Related Keywords

No Related Keywords

Register NowHow It Works Need Essay Need Essay
GCSE CHEMISTRY COURSEWORK: Titrations
1 User(s) Rated!
Words: 2086 Views: 585 Comments: 0
Titrations Introduction: In this experiment we are going to be testing to see which antacid tablet works the best in helping us get rid of stomache aches. From our preliminary experiment, the results we got told us that Rennie was the best antacid tablet with the most accurate results and was also the best tablet in strength. Neautralisation basically occurs when the right amounts of acid and alkaki react. Aim: The aim of this experiment is to find out which antacid tablet works the best in removing stomache aches the quickest. Key Factors: In...
weights and by taking 1g pf each tablet our results would be fair.

To make our method more accurate we could test each tablet on people who have stomache aches and see which one is more effective. We could also test the pH of a stomache and see which tablet would be most suitable.

Another improvement to our experiment would be to get slices of the stomache and let it grow to see what happens and then test the tablets. We could also do the test more times and see if we get the same results.

Become A Member Become a member to continue reading this essay orLoginLogin
View Comments Add Comment

HYPOTHESIS We can recognize four... HYPOTHESIS We can recognize four types of substances due to their structure: ionic, metallic, covalent, and molecular. If a given substance has a metallic luster, is malleable and ductile, is a good conductor of heat and electricity, and has high melting and boiling points, than it is supposed to be a giant metallic structure. If a given substance has low melting and boiling points and does not conduct electricity, it surely is a molecular structure. If a given substance is soluble in water and in other polar solvents, if it conducts electricity after being melted or dissolved, and if it has high melting and boiling points, we can predict that it is a giant ionic structure. So we will have to check which of these properties does a given substance have. APARATUS spatula stirring rod open electric circuit batteries, light bulb, electric wire with two dismantled endings two metal plates the first made of copper, the second made of zinc plastic wash bottle test tubes in amount of 4 watch glasses in amount of 5 Bunsen burner test-tube rack porcelain crucible crucible tongs triangle tripod I decided to use separate watch glass for each substance to avoid possible laboratory errors resulting from contamination with the previous one. CHEMICALS substance A "“ white, granulated powder substance E "“ silver nodules, apparent metallic luster substance C "“ tiny, white crystals substance D "“ a bit larger white crystals substance B "“ black powder distilled water SAFETY RULES Be careful while burning substances in a flame! Don't put your hand into water when the electric current flows "“ you can have your skin seriously damaged! Do not touch hot crucible with bare hand, use crucible tongs! PROCEDURE I put a few grams of each substance except for substance E, which I put into a watch glass using a spatula into separate test tubes, placed in a test tube rack. I put a hint of each substance into separate watch glass. I use open electric circuit in order to investigate electric conductivity of each substance in solid state. I pour a few droplets of water into each watch glass using plastic wash bottle. Then I mix each substance with a stirring rod in order to make process of dissolving faster and more effective. I put two metal plates into each watch glass, so they are partly sunk in the water or solution, if it was formed in the manner one ending of the electric wire sticks to the first plate, and the second ending sticks to the second plate, and it is important that plates do not touch each other. Then I observe whether the light bulb is shining. I take a hint of each substance one by one, using a spatula. I put each substance into a porcelain crucible. I put crucible on a triangle placed on a tripod above the Bunsen burner. Then I turn the burner on and wait up to a minute in order to check whether the melting point is low or high. To handle the crucible I use crucible tongs. Note: I carefully clean spatula before using it again and again, I do the same with the stirring rod and porcelain crucible. DATA COLLECTION A B C D E Conductivity in solid state - + - - + Conductivity after being dissolved - - + - - Solubility in water + - + - - Melting point low high high high high CONCLUSION Substance A is soft and granulated. This substance has low melting point, what indicates that the intermolecular forces are weak. It does not conduct electricity, because molecules are not charged. So substance A has undoubtedly molecular covalent structure. However, on contrary to other substances with molecular covalent structure, it is quite soluble in water, what means that its' molecules can form hydrogen bonds to the water to compensate for the water-water hydrogen bonds broken. Example of such molecules are sugar molecules, so this substance is probably sucrose. In the case of the substance E there is an apparent metallic luster, so it has the giant metallic structure. This metal has high melting point, because it takes a lot of energy to break up a lattice of ions in a sea of electrons with strong forces of attraction, called metallic bonds, between them. Metals are good conductors of electricity because the delocalized, free electrons can move through the lattice carrying charge, when a voltage is applied across the metal structure. The substance C is the only substance aqua solution of which conducts electricity, so it has to have giant ionic structure. It's because the water molecules, which are dipoles, can attract the ions away from the lattice. The ions move freely, surrounded by water molecules. Dissolved or melted ionic compound conducts electricity, because the lattice breaks up and the ions are free to move as charged particles. It can be assumed that substance D is a giant covalent structure, because it is insoluble, it is very hard, but brittle, it forms crystal lattice, and it has high melting point. In addition, this substance does not conduct electricity at all. Substance B is soft and brittle in touch - the sheets can slide over each other easily. It may indicate that this substance has a molecular structure, like the first one. But it has much higher melting point than molecular substances. Besides that, it conducts electricity in solid state, and it does not dissolve in water. This set of properties is very specific "“ it is a combination of single properties of different types of structures. The fact that this substance could well be used as a lubricant layers are easily rubbed off could indicate that this substance can be graphite. EVALUATION After an experiment was finished, our chemistry teacher wrote the names of substances that we were to determine structures of, on the blackboard, so we could verify if our findings were correct and propose improvements to the method in case they were not. And so: substance A appeared to be glucose, substance B "“ graphite, substance C "“ sodium chloride, substance D "“ silicon dioxide, and substance E "“ chromium metal. My predictions according to substance A appeared to be correct. In case of substance E, which is chromium metal, I also obtained correct results. I think that this substance, like it is in case of all metallic substances, has a structure very easy to determine experimentally, even, to say, with bare eye, because we know that metals are the only type of substances that perform a property called metallic luster. Other properties I observed also form a set of properties typical for metal, which is chromium in this case. I was right in case of substance C, which, as it appeared later, is sodium chloride, and sodium chloride is the most characteristic representative of ionic substances. My assumptions relating to substance D are also proved to be correct, since I know now that this substance was silicon dioxide, commonly occurring as quartz, being a good exemplification of properties connected with a giant covalent structure. In case of substance B, I was again right, due to the fact that this substance appeared to be graphite, as I have predicted. Graphite is another example of giant covalent structure, but, on contrary to silicon dioxide, it conducts electricity "“ this property is specific only for this particular substance.   

HYPOTHESIS We can recognize four types of substances due to their structure: ionic, metallic, covalent, and molecular. If a given substance has a metallic luster, is malleable and ductile, is a good conductor of heat and electricity, and has high melting and boiling points, than it is supposed to...

Words: 1217 View(s): 301 Comment(s): 0
I am measuring the... I am measuring the rate of reaction how fast a reaction takes of sodium thiosulphate and hydrochloric acid. There are different variables I could use to see the change in the rate of reaction. These include temperature, concentration or catalysts. I am going to do two experiments, one changing the temperature and one changing the concentration of the sodium thiosulphate. This is how they will be done. Planning Experimental Procedures Equipment Sodium thiosulphate Na S O of different concentrations Hydrochloric acid HCl Tile marked with a cross Measuring cylinder x2 Beaker x2 Bunsen Tripod Test tube x2 Stopwatch Thermometer As the diagrams show, firstly I will measure the right amount of sodium thiosulphate and hydrochloric acid into two separate test tubes. If it is needed, these will then be put into water and heated with a Bunsen burner and tripod until they are up to temperature, which will be measured with a thermometer in the water. They will then be put into the beaker. Firstly, the experiment will be done with the substances at room temperature. This means that the beaker will be filled with Na S O and HCl via two measuring cylinders and placed on the tile marked with a cross. The amount of Na S O and HCl being put in the beaker will be determined by prior tests, but they will only need to be quite small amounts. As soon as the two substances are mixed together, the stopwatch will start timing and it will stop when the cross is obscured. When the substances need to be heated, they will be put in separate test tubes and heated in a beaker of water as above. They will be mixed together when up to temperature. One of the experiments will show the difference temperature makes and the other will show the difference the concentration of the sodium thiosulphate makes. During the experiments, goggles and aprons will be worn at all times for safety. The tests will be made fair by the fact that only one thing will be changed each time "“ the temperature or concentration of the sodium thiosulphate. We presume that when the concentration of the Na S O is increased, the rate of reaction will be higher. This is because if there are more molecules, they are more likely to collide and react. However, the collision theory says that a very small percentage of these collisions results in a reaction. This is because of an energy barrier. Only those particles with enough energy to overcome the energy barrier will react when they collide. So, if the frequency of collisions is increased, the rate of reaction will increase. However, the percentage of successful collision will remain the same. The particles go through random collisions in which energy is transferred between the colliding particles and this leads to particles with differing energies. The distribution of the energies of a particle of gas is shown by the Maxwell-Boltzmann energy distribution curve, shown below. We would also presume that when the temperature is increased it will have the same effect. This is because the molecules will collide more often and with greater energy and so will be more likely to successfully react because their bonds break. For an average reaction a 10 C temperature rise doubles the rate of reaction because about twice as many particles possess the necessary activation energy. The next diagram shows Maxwell-Boltzmann distribution curves for a fixed mass of gas at two temperatures T and T where T is about 10 C higher than T . The total area under the curve remains the same since there is no change in the number of particles present. So, I predict that in the experiment were the temperature is varied, the rate of reaction will go up as the temperature goes up. In the experiment where the concentration of the thiosulphate is to be varied, I expect the rate of reaction to go up as the concentration goes up. If the concentration doubles, I would expect the rate of reaction to double and if the concentration is zero I would expect the rate of reaction to be zero. In the graph showing temperature compared to rate of reaction, I would expect there to be negative correlation and in the graph showing concentration compared to rate of reaction, I would expect there to be negative correlation. However, it remains to be seen if the results will follow this theory. Here are the results tables that will be used: Temperature 1st results 2nd results Average Rate Of Reaction C seconds seconds seconds seconds Room approx.20 30 40 50 60 70 This is for the first half of the experiment where everything will be kept the same except the temperature which will range from 20 C to 70 C. It is hoped that there will be sufficient time for two experiments and an average will be calculated afterwards. The concentration of the sodium thiosulphate used throughout will be 30g/dm. Concentration 1st results 2nd results Average Rate Of Reaction g/dm seconds seconds seconds seconds 15 20 25 30 35 40 This is the other section to the experiment where everything will be constant apart from the concentration of the sodium thiosulphate. It has been decided that a concentration of no less that 15g/dm will be tested because any less than this would probably take too long. The hydrochloric acid and the sodium thiosulphate will not be heated and the tests will be done at room temperature, usually around 20 C. The experiment will be done twice or three times if possible and the results will be made fair by the fact that only one thing will vary each time. Goggles and aprons will be worn at all times for safety. It has been decided that 5ml of HCl and 20ml of Na S O will be used. Obtaining Evidence These are the results of the experiments: Temperature 1st results 2nd results Average Rate Of Reaction C seconds seconds seconds secs Room approx.20 74.5 69.9 72.2 13.85 30 38.1 38.3 38.2 26.18 40 35.9 39.4 37.65 26.56 50 20.7 18.1 19.4 51.55 60 12.3 9.9 11.1 90.09 70 5.9 5.2 5.55 180.18 Concentration 1st results 2nd results Average Rate Of Reaction g/dm seconds seconds seconds secs 15 125.2 123.5 124.35 8.04 20 74.5 69.9 44.2 13.85 25 53.6 51.2 52.4 19.08 30 49.6 51.6 50.6 19.76 35 45.7 48.8 47.25 21.16 40 22.6 30.5 26.55 44.35 Analysing evidence and drawing conclusions All results have now been obtained and they seem to be quite good, all showing correlation. As was hoped at the start, a repeat was managed for each test and an average worked out from those figures. The results were recorded with decimal place and the averages and rate of reactions are to two decimal places. The rate of reaction is the key thing being looked at in this experiment and this is how it was calculated: 1 Time taken for cross to be obscured This figure was then multiplied by 1000 to make it easier to deal with. The figures have all been rounded to two decimal places. My predictions have been correct. When the concentration of the sodium thiosulphate has gone up, as the first part of the experiment shows, the rate of reaction goes up. When the temperature goes up, as the second results table shows, so does the rate of reaction. This is what was expected and therefore makes it highly unlikely that there have been any major mistakes, although all results are obviously not perfect. The next three pages are graphs. Graphs one and two relate to the first table of results and graph three relates to the second table. The reason there are two graphs for the first table is that one shows time taken for cross to be obscured and the other shows rate of reaction. Rate of reaction is what is being investigated and so only a rate of reaction graph was needed for table two. There are two graphs for the first results table to show the difference in time taken and rate of reaction i.e. the time taken for cross to be obscured shows negative correlation while graph two shows positive correlation. By drawing a line of best fit on the rate of reaction graphs, we can see that there are no results that are obviously completely wrong. With both graphs the last result is suprisingly high, and this can be seen on the results table as well. Evaluating Evidence The procedure used was good and produced good results but it could have been improved and these will be listed later. The results are mainly good, there are no odd results and everything came out as expected. This could mean that the experiment was done perfectly but it doesn't. Although all the average times and rates of reaction all conform to a pattern, they are not all evenly spaced and therefore are probably not perfect. As an example, in the first experiment, where the temperature was being varied, the rates of reaction of 30 C and 40 C were 26.18secs and 26.56secs respectively. This was only an increase of 0.38secs compared to an increase of 90.09secs for 60 C to 70 C from 90.09secs to 180.18secs . Clearly this is an enormous difference and disproportionate. The results could be correct but the results do appear to nearly double each time, except for in this instance. There are similar examples from the second experiment but they are not as obvious. Improvements that could be made if the experiment was repeated: When doing the results that took less time some took around five seconds, it would have been more accurate to have two people so one person could put the substances together while the other person started timing Obviously it would have been good to have done more repeats. Two tests were managed each time but if one had been wrong this could have dramatically changed the average time and therefore rate of reaction. Increasing the surface area of a reactant will increase the rate of a reaction. This is because the reacting particles can only collide with he surface of the solid and the particles within the solid cannot react until those on the surface have reacted and moved away. Powdered calcium carbonate has a much larger surface are than the same mass of marble chips and therefore will react more quickly. All in all I think this was a good experiment and the best that could have been done with the time and resources available. The results supported my predictions and they seem to be fairly reliable results. Aim : We did 4 experiments to find out how the rate of reaction changes with differing concentrations of Sodium Thiosulphate, Hydrochloric Acid and water. As an inert and stable liquid, water was used to alter concentration of Sodium Thiosulphate without changing the end amount of solution. All the atoms in a water molecule have a full outer shell, so they would not react with the other chemicals. WATER IS USED TO SLOW THE REACTION SO THAT IT IS EASIER TO TIME HOW LOG   

I am measuring the rate of reaction how fast a reaction takes of sodium thiosulphate and hydrochloric acid. There are different variables I could use to see the change in the rate of reaction. These include temperature, concentration or catalysts. I am going to do two experiments, one...

Words: 2030 View(s): 661 Comment(s): 0
Acid Limestone SC1 HF Planning...Acid Limestone SC1 HF Planning We are going to investigate the factors that affect the rate of a chemical reaction. Input Variables of this investigation I could study are: Amount of Calcium Carbonate CaCO3 Temperature of Acid Concentration of Acid molarity Surface Area Amount of Acid Gas Pressure The Variable I have chosen is the Concentration of Acid molarity. My prediction is that if the concentration of the acid increases there will be an increase in the rate of reaction for example the highest concentration will have the fastest reaction time with the Calcium carbonate to produce Carbon Dioxide. I think this will happen because activation energy is an amount of energy needed for a reaction to occur; this amount varies from different elements and type of reaction. This may save energy for industrial use, as they will only supply the amount of energy needed exactly and not more. The Collision Theory, from the kinetic theory of gases, the collision theory of bimolecular reactions in a gas phase was developed. In a reaction between two gaseous substances A&B a molecule of A must collide with B for the reaction to proceed but in a concentrated solution there will be a higher percent of reactants which will have no more energy. Not all collisions cause a reaction, only the ones which reach the activation energy of the reaction. If a solution is more concentrate it means there are more particles of reactant knocking about between the water molecules, which makes collisions between important particles more likely. In a gas, increasing pressure means the molecules are more squashed up together so there are going to be more collisions. Reactions only happen if the particles collide with enough energy. This is called initial energy, is known as the activation energy, and is needed to break the initial bonds shown in the diagrams below. The more often the particles collide and the harder they hit, the greater the reaction rate. This is why I predict that the rate of reaction will increase as the concentration of a solution increases. The higher the concentration of the hydrochloric acid is, the higher the chance of the bonds breaking because the stronger the hydrochloric acid is the more energy the molecules have so they travel with more force which means the bonds break. They get this energy from colliding with each other this is why the higher concentrated acids have more energy as they have more particles to collide with to produce energy. If the molecules do not have much energy they will just bounce of the bonds harmlessly. The energy is needed to break the bonds and get the reaction started. Rates of reaction can be changed not only by catalysts but also by changes in temperature and by changes in concentrations. Increasing the concentration can also increase the reaction rate by increasing the rate of molecular collisions. Image to show the collision theory and why by increasing the concentration of the acid the more likely the acid particles will hit the calcium carbonate bond in the correct place. The line has the classic shape of a rate of reaction graph. It starts off steep, becoming shallower until it levels off. You can tell the rate of reaction at any particular time by the slope gradient of the line. The word equation for this experiment is: CALCIUM CARBONATE + HYDROCHLORIC ACID=CARBON DIOXIDE+ WATER + CALCIUM CHLORIDE CaCO3 + 2HCl = CO2 + H20 + CaCl2 Fair Test Details The input Variable I am going to change is the concentration of acid. The variables I need to keep the same are: Amount of Calcium Carbonate CaCO3 Temperature of Acid Surface Area Amount of Acid Gas Pressure The outcome variable I am going to measure is the amount of Carbon Dioxide given off in 1 minute. The other outcome variables I could have measured are: How long it takes to produce 100ml of Carbon Dioxide, I have chosen the concentration of acid as my input variable as it is one of the easier variables to control, as variables like temperature and surface area are hard to either keep at a constant temperature or get the surface area the same each time you repeat the experiment. I will use the following equipment in my experiments: 10g-15g Marble Chips, 1 Conical flask, 1 Thistle Funnel, 25ml dilute Hydrochloric Acid, 1 Delivery Tube, 1 Gas Jar, 1 Bee Hive Shelf, 1 Measuring Cylinder, 1 Tub of water, 1 Bung, 1 Thermometer, 1 Greasy lid for gas jar, 1 Stopwatch, 1 Set of Scales, Distilled Water, 1 pair of Goggles, 1 Bench Mat, 1 Sieve. I will weigh out the marble chips on the scales so I have exactly the same mass of marble chips each time to make it a fair test. I will then place the chips in the conical flask, and place the airtight bung in the top so no Carbon Dioxide will escape making it a fair test. The bung will have the thistle funnel attached to it and the delivery tube. I will make sure the thistle funnel tube is touching the bottom of the flask so no carbon dioxide can escape that way. I will pour the 25ml of hydrochloric acid into the conical flask through the thistle funnel so that all the carbon dioxide is captured and non-can escape so it is a fair test. The carbon dioxide cannot escape through the thistle funnel, as the bottom of the tube will be submerged in acid if it is touching the bottom of the conical flask making it impossible for the gas to travel up it. The delivery tube will take the carbon dioxide produced up through the bee hive shelf and into the gas jar filled with water, as the carbon dioxide is produced it will push the water out of the jar and at the end of the experiment we can measure how much gas was collected by the amount of water we need to refill the gas tube to repeat the experiment. We will the gas jar to the top with water and then slide the greased lid across the top that makes sure the gas jar is full to the top. We will pull the end of the delivery tube up through the hole in the beehive shelf. The beehive shelf is then placed in the tub of water that goes about 4-5cm over the top of it. We will then put the gas jar with lid in the tub filled with water, we will then slide the greasy lid of the top and carefully keeping the top of the jar under the water place the open end of the jar on top of the beehive shelf over the top of the delivery tube so the carbon dioxide produced will be able to go straight into it, making it easier to record how much was produced. We use the measuring cylinder to measure how much water is needed to top up the gas jar after each experiment to wok out how much gas was produced. To make the measuring easier we can put an elastic band around the gas jar where the water level is at the end of each experiment so it is easier to measure. We will need the stopwatch to time the minute for the experiment so we will know when to stop the experiment and measure how much gas has been produced. I will use the Distilled water to dilute the acid to give me other concentrations to experiment with. I will try to take 4 "“ 5 readings for each concentration of acid as it will give us a clearer pattern and will make it easier to spot anomalous results so my average will be more accurate. I will use the concentrations of acid within the rage of 0.5m and 2m, as these are the acids available to us in school at the moment. I will be able to change the concentrations of the acids by diluting them with distilled water this will give us other concentrations giving us a wider range of concentrations to work with. I will make sure that I dispose of the left over marble chips correctly so the sink doesn't get blocked with the un-reactive pieces ate the experiment. I will make sure that the bung is on the conical flask securely in case of a violent reaction so it doesn't harm anyone. I will wear goggles to make sure that the acid doesn't go in my eyes. I will be careful when carrying or handling the glass equipment so not to drop it or cut my self with it. I will be careful when handling the acid, by not to using too much and making sure that any spills are mopped up straight away. I will make sure I keep an eye on my experiment so I get reliable results and also so it doesn't react to vigorously. Concentration of acid. M Amount of Carbon Dioxide produced in 1 min ml 1 2 3 4 5 Average 0.5 M 0.75 M 1 M 1.5 M 2 M Preliminary Work I hope to find out: How much Hydrochloric acid to use, What temperature is the best for getting my chemicals to react, How many grams of marble chips work best, How long too time for, for the best results i.e. 1 or 2 minutes. In my Preliminary work I took 0.5m acid and 2m hydrochloric acid as these are the highest and lowest concentrations of acids I am going to use. I did this to test to see how large a gas jar I needed and how easy it was going to be to carry out my experiment. I found that I needed a gas jar that could contain about a litre of water for my experiment as if the gas jar was any smaller the 2m acid would react to produce to much carbon dioxide to be measured accurately. I also found that the reaction wasn't as violent if I use only 20ml of acid instead of 25ml, this was enough to cover all of the marble chips but didn't produce to much carbon dioxide for me to measure. By using 15g of marble chips slowed down the rate of the reaction as there was more for the acid to react with which made the product easier to measure. Amount acid Concentration Result 25 ml 0.5 M 85 ml 25 ml 2 M Emptied gas jar. 20 ml 2 M 323 ml 20 ml 0.5 M 82 ml Obtaining Evidence Concentration of acid m Amount of Carbon Dioxide produced in 1 min ml 1 2 3 4 Average 0.5 M 40 ml 75 ml 76 ml 72 ml 74.33 ml 0.75 M 97 ml 115 ml 120 ml 105 ml 109.25 ml 1 M 190 ml 165 ml 157 ml 175 ml 171.75 ml 1.5 M 234 ml 200 ml 240 ml 221 ml 223.75 ml 2 M 225 ml 301 ml 320 ml 323 ml 314.66 ml Results from another group doing the same experiment using the same variable. Concentration of acid m Amount of Carbon Dioxide produced in 1 min ml 1 2 3 4 Average 0.25 M 23 ml 34 ml 19 ml 31 ml 26.75 ml 0.5 M 67 ml 75 ml 78 ml 64 ml 71.0 ml 1 M 169 ml 221 ml 175 ml 174 ml 172.66 ml 1.5 M 265 ml 276 ml 279 ml 273 ml 273.25 ml 2 M 383 ml 358 ml 370 ml 376 ml 376.33 ml Circled and pink results are the anomalous results, which are not included in the average. Analysis At the end of the experiment there was more gas produced by the 2m hydrochloric acids reaction than the 0.5m hydrochloric acids reaction. The higher the concentration of acid the faster the reaction and so more gas was produced in the minute. The lower the concentration of acid the less gas was produced, as the reaction takes longer. This is because a high concentrated substance has more particles, this means that the reaction is quicker because the reactant has more particles to collide with and so reacts faster. This happened because activation energy is an amount of energy needed for a reaction to occur; this amount varies from different elements and type of reaction. This may save energy for industrial use, as they will only supply the amount of energy needed exactly and not more. The Collision Theory, from the kinetic theory of gases, the collision theory of bimolecular reactions in a gas phase was developed. In a reaction between two gaseous substances A&B a molecule of A must collide with B for the reaction to proceed but in a concentrated solution there will be a higher percent of reactants which will have no more energy. Not all collisions cause a reaction, only the ones which reach the activation energy of the reaction. The higher the concentration of the hydrochloric acid is, the higher the chance of the bonds breaking because the stronger the hydrochloric acid is the more energy the molecules have so they travel with more force which means the bonds break. They get this energy from colliding with each other this is why the higher concentrated acids have more energy as they have more particles to collide with to produce energy. If the molecules do not have much energy they will just bounce of the bonds harmlessly. The energy is needed to break the bonds and get the reaction started. Rates of reaction can be changed not only by catalysts but also by changes in temperature and by changes in concentrations. Increasing the concentration can also increase the reaction rate by increasing the rate of molecular collisions. If a solution is more concentrate it means there are more particles of reactant knocking about between the water molecules, which makes collisions between important particles more likely. In a gas, increasing pressure means the molecules are more squashed up together so there are going to be more collisions. Reactions only happen if the particles collide with enough energy. This is called initial energy, is known as the activation energy, and is needed to break the initial bonds. The more often the particles collide and the harder they hit, the greater the reaction rate. If the experiment is completed with a high concentrated acid, the hydrogen is evolved much more quickly, making the liquid fizz. This is because the rate of reaction depends upon how frequently the molecules of the reacting substance collide. The concentrated acid has more molecules for a given volume than the more dilute acid. This is because there are more molecules about, the frequency of the collisions is greater, and the reaction is faster. Both of my graphs and my hypothetical graph from my plan show me that the higher the concentration of the acid the faster the reaction and the more product is produced in the time given. On the graph to show my results I have one anomalous result, this is at 1m of acid, but apart from this the rest of my results fit into my best-fit curve. All my graphs are of a similar nature and show the same thing this makes me confident in my readings. Evaluation For each concentration of acid the results seemed to come out close together which gave me confidence. I found it difficult to make accurate readings as gas could easily escape as not all of the equipment was as air tight as it could have been and I could have made silly mistakes as we were pushed for time and so we rushed a bit while carrying out the experiment. There are two reasons why I thought my results wee accurate. Firstly in most cases the amounts of Carbon Dioxide given off during the reactions were quite close together. Secondly the graph shows a clear pattern showing the different amounts of Carbon Dioxide produced for each concentration of acid. I spotted two anomalies which I ringed but ignored these when working out the averages, for my results and the other groups results which are included in my obtaining evidence. Taking 4 readings allowed me to even out the difficulties of measuring the amount of Carbon Dioxide produced in a minute for each concentration of acid, as it was difficult to pull the delivery tube out of the gas jar exactly after one minute, also gas could have been lost through the thistle funnel and through the gap between the bung and the conical flask or any other air tight materials these were all slight human errors which could have caused some of my anomalous results. The method worked quite well because most results seemed consistent. There were a few problems capturing the gas accurately because it was difficult to prevent leaks in the equipment if there were any. Sometimes the acid didn't cover all of the limestone, so I would have to next time make sure I choose flatter pieces of limestone to make sure it was all covered by the acid. Also the conical flask that the reaction was taking place in was getting slightly warm after each experiment this may have changed my results slightly. I would use a different conical flask each time to prevent temperature rise if I repeated the experiment. The fastest concentration of acid to react was the highest concentrated. The graphs show this clearly. The one 'odd' result ringed at 1 m acid on the graph was over average. This may have occurred by an inaccurate reading or by mixing unevenly as I may have mixed some acids more or less than others. However ignoring this, the other readings were consistent. The results covered a wide range of the concentrations available to us and agreed with the results of the rest of my class, who tried out different concentrations of acid. There are several ways I could improve the way the gas is collected. There are several ways in which this experiment can be extended. The surface area of the limestone used could be used, but would be very time consuming as each time the experiment was repeated we would need to make sure that the limestone was ground to the same size each time otherwise this would not be a fair test. Temperature could be altered to extend this experiment, but I would have to be careful when heating the acid not to go above 70°c as above this temperature the acid starts to decompose. Similar equipment would be needed for both of these experiments, for the surface area of the limestone we would need to use a mortise and pestle to grind it up to different surface areas, for the temperature variable we would have to use ice and a Bunsen burner to establish different temperatures. As one the products, is in the form of gas, another way of extending the experiment is to use different reactants and keep the variables the same, as you can control the concentration of the substrate and collect the gas given off from the reaction between the substrate and the enzyme. The volume of the product can be measured to demonstrate the difference of the reaction when certain factors are changed. Enzymes are made to e specific; this means that they can have only one substrate that they will wok on. Each enzyme has an active site that is where their own specific substrate's molecules will fit. Enzymes all work best at optimum temperature that is usually body temperature at 37°C. If the temperature that the enzyme has to work at gets to high, normally 40°C it will start to become denatured and therefore no longer wok on it's substrate as the active site has changed shape. Also enzymes usually wok best at an optimum pH level, this is normally seven because enzymes are proteins, which are damaged by very acidic or very alkaline conditions. Most reactions work better at higher temperatures, this is because molecules move around much quicker. This makes the molecules have more chance to collide with the substrate. With more collisions there is more chance of a reaction-taking place. This makes the rate of reaction faster. At 40°C the enzymes start to get damaged, this slows down reaction and by around 60°C the enzyme will be completely destroyed. SUBSTRATEGLUCOSE SOLUTION + EMZYMEYEAST GAS PRODUCTCARBON DIOXIDE + LIQUID PRODUCTALCOHOL + CHEMICAL PRODUCT + ENERGY   

Acid Limestone SC1 HF Planning We are going to investigate the factors that affect the rate of a chemical reaction. Input Variables of this investigation I could study are: Amount of Calcium Carbonate CaCO3 Temperature of Acid Concentration of Acid molarity Surface Area...

Words: 3539 View(s): 253 Comment(s): 0
I will be investigating how... I will be investigating how the concentration of hydrochloric acid affects the rate of reaction between hydrochloric acid and magnesium ribbon. Equation: Mgs+2HClaq→MgCl2aq+H2g Planning: The input variables are: "¢ temperature of acid "¢ concentration of acid "¢ surface area of magnesium "¢ use of catalyst I will measure the concentration of acid and control the temperature of acid, surface area of magnesium, mass of magnesium and use of catalyst. The temperature of the acid will effect the rate of reaction because as the acid particles heat up, they gain kinetic energy, therefore move faster and collide more often and more successfully because the collisions are more energetic, therefore there are more collisions in a given time, and the rate of reaction increases. The surface area of the magnesium will effect the rate of reaction because the larger the surface area, the more collisions can take place in a given time, and the rate of reaction increases. The use of a catalyst will effect the rate of reaction because they give an alternative pathway that has a lower activation energy, therefore more of the collisions will result will result in reaction because they need less energy to be successful. This is the apparatus I will use: I will place some magnesium in a flask with an amount of acid. I will place a bung on the tube to prevent any gas from escaping. A tube will run from the flask to a graduating tube in a trough, both filled with water. I will then measure the amount of gas given off in a certain time. I will repeat the experiment 3 times in order to highlight any anomalies. In order to work safely, I will wear goggles in order to protect my eyes from acid. Prediction: I predict that the higher the concentration of the acid, the faster the rate of reaction. This is because there will be more acid particles in a given volume, therefore there are more collisions in a given time, and the rate of reaction increases. If the concentration was to double, I would expect the rate to double. This is in reference to a previous experiment with a reaction between marble chips and various concentrations of acid. It was proved in this experiment that doubling the concentration of the acid doubled the rate of the reaction, therefore the two sets of results were directly proportional. Pre-test: The concentrations we decided to use as our upper and lower values were 2M and 0.2M. From our pre-test, we discovered that 0.2M took too long to react, so the concentrations that we chose were not workable. We then decided to change our lowest concentration to 0.6M. Concentration of Acid M Time to react seconds 2 8.81 0.6 65.90 From the results of my pre-test, I will use 3cm of magnesium and measure the time to collect 10cm3 gas, as these provided workable results. Obtaining Evidence: Concentration of Acid M 1 2 3 2.0 8.52 7.84 8.42 1.8 11.52 6.49 9.12 1.6 9.35 16.02 10.01 1.4 13.95 11.58 11.21 1.2 13.25 13.78 16.05 1.0 18.81 18.24 20.72 0.8 32.78 32.81 22.02 0.6 67.51 48.28 62.46 Concentration of Acid M Temp Before ˚C Temp after ˚C Temp Before ˚C Temp after ˚C Temp Before ˚C Temp after ˚C 2 23 29 20 20 23 30 1.8 23 29 22 22 23 30 1.6 23 29 22 22 24 28 1.4 23 30 21 21 23 27 1.2 23 31 23 23 24 27 1 23 27 23 23 24 27 0.8 23 25 23 23 24 26 0.6 21 23 22 22 23 25 Concentration of Acid M Average Time seconds Rate x100 2 8.260 12.107 1.8 10.185 9.818 1.6 10.010 9.990 1.4 12.246 8.166 1.2 14.915 6.705 1.0 19.256 5.193 0.8 29.203 3.424 0.6 64.985 1.539 Results in bold are anomalies. Analysing and Conclusions From the temperatures taken before and after the reaction, I have discovered that the reaction is exothermic. My graphs show that the higher the concentration of acid, the faster the rate of reaction. This is because there are more acid particles in a given volume, therefore more collisions in a given time, therefore increasing the rate of reaction. If the concentration was doubled, there would be double the amount of acid particles in a given volume, double the amount of successful collisions in a given time, therefore the rate of reaction should double. This means that the concentration of acid and rate of reaction are directly proportional, as stated in my prediction. However, form looking at my results table, I have discovered that the rate of reaction is the concentration of the acid squared. This disagrees with my original prediction. Evaluating: The readings on my graph do not fit the best-fit line very well, as there are several anomalies, therefore the results are not very reliable. The anomalies could be due to the fact that we had to use two different bottles of acid during the experiment, so the concentrations could have been slightly different. We did parts of our experiment at different times, so the temperature in the lab could have been higher, therefore increasing the temperature of the acid, so the particles would have more energy, move faster, increasing the number of collisions, therefore altering the rate of reaction. Where the magnesium had oxidised, a substance had formed on the surface on the magnesium, which meant that the acid had to get through it to reach the magnesium, increasing the time to react. We did however try to make our data more accurate by using a syringe to measure small amounts of acid and water, and using as many decimal places as we could in our calculations. The temperature of the acid was hard to control, as it was controlled by the temperature of the room. If I was to repeat the experiment, I would use more varied concentrations in order to show more clearly the pattern, and also to attempt to clear any anomalies. I would also like to investigate larger concentrations of acid, but would have been hard to measure.   

I will be investigating how the concentration of hydrochloric acid affects the rate of reaction between hydrochloric acid and magnesium ribbon. Equation: Mgs+2HClaq→MgCl2aq+H2g Planning: The input variables are: • temperature of acid • concentration of acid • surface area of magnesium ...

Words: 1207 View(s): 326 Comment(s): 0