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Rate of Reaction - Sodium Thiosulphate and Hydrochloric Acid
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?Aim??Investigation, to find out how the rate of reaction between Sodium?Thiosulphate and Hydrochloric acid is affected by changing the?concentration.??Introduction??I must produce a piece of coursework investigating the rate of?reaction, and the effect different changes have on them. The rate of?reaction is the rate of loss of a reactant or the rate of development?of a product during a chemical reaction. It is measured by dividing 1?by the time taken for the reaction to take place. There is five?factors which affect the rate of a reaction, according to the?collision theory of reacting particles: temperature, concentration of?solution, pressure in gases, surface area of...
due to?time restrictions.??· I used ICT to display my coursework, but I did not use it in anyway?that affected the experiment.??· I would like to do a further experiment to confirm my results.?However I am restricted by time and the available facilities which?means I cannot repeat it.??· Also instead of using a cross on a piece of paper I could use a?single beam of light until it could no longer be seen??· Use of computer to aid analysis of results??· Carry out all of the experiments on same day to improve accuracy??· Calculate more than ten tangents to improve accuracy?
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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...

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Aim: To investigate... Aim: To investigate the rate of reaction between Hydrochloric acid and marble chips. Background Knowledge: Factors that affect the rate of reaction between hydrochloric acid and marble chips or any other reaction are called variables. They are: ¨ The surface area of the chips Solids with a large surface area react faster than solids with a smaller surface area. This is due to the fact that if there is more area on the solid to react with the substance the reaction is able to occur much faster. Page 79 "“ GCSE Chemistry revision Guide This diagram shows a large particle small surface area and lots of small particles large surface area and how the particles can react with more area on the smaller pieces. ¨ The temperature of the acid The more heat particles have, the more energy they have. So if the particles have more energy they're going to move around faster. As they're moving around faster, there's more chance of collisions. So the higher temperature increases collisions therefore speeds up the reaction. Page 79 "“ GCSE Chemistry revision Guide This diagram shows the difference in movement between hot and cold particles. ¨ The concentration of the acid As the concentration increases, the rate of reaction increases. This, like the temperature of the acid, is based on the collision theory. The higher the concentration, the more particles therefore the more collisions so the reaction takes place faster. Page 79 "“ GCSE Chemistry revision Guide This diagram shows the movement and difference between a low concentration of particles and a high concentration of particles. ¨ Catalysts A catalyst speeds up a reaction. It does this by lowering the activation energy. The activation energy is what is needed to turn reactants marble chips into products hydrogen gas. To make reactants turn into products a sufficient amount of energy is needed to make the particles collide to start the reaction. This is activation energy and it gives an exothermic reaction the energy it needs to continue the reaction. Catalysts lower the activation energy so it is easier for particles to react so a lot more particles have enough energy to react, therefore, speeding up the rate of reaction. Page 79 "“ GCSE Chemistry revision Guide This diagram shows how a catalyst gives particles something to stick to, increasing the number of collisions. Page 80 "“ GCSE Chemistry revision Guide This graph shows the effect of a catalyst on the rate of reaction. The factors that affect the rate of reaction are all based on the collision theory. The theory that all particles have to collide to cause a reaction. Preliminary work: To investigate the different concentrations of the acid would be the easiest to measure conducted over a short period of time and satisfactory results would be produced. To measure the rate of reaction, the amount of gas given off could be measured. From the equation: CaCO3 + 2HCL à CaCL2 + H20 + CO2 It is seen that a gas is produced, CO2 so the amount of gas that is produced at different concentrations could be measured. A mole calculation was used to find out how much Calcium Carbonate to use. If I use a 100cm3 measuring cylinder to measure gas: 24000cm3 of gas is 1 mole of gas 100/24000 = 1/240 = 4.2 x 10-3 moles CaCO3 : CO2 1 : 1 1 mole : 1 mole 100g : 44g 4.2 x 10-3 m : 4.2 x 10-3 m 4.2 x 10-3 m x 100g = 0.42g 0.42g of calcium carbonate should produce 100cm3 of gas. Therefore, the minimum of calcium carbonate I will use to get sufficient results is 0.5g. I will be using five different concentrations of acid: 100%, 75%, 50%, 25% and 0%. So the amount I will use will be: 100% = 20cm3 HCL 0cm3 Water 75% = 15cm3 HCL 5cm3 Water 50% = 10cm3 HCL 10cm3 Water 25% = 5cm3 HCL 15cm3 Water 0% = 0cm3 HCL 20cm3 Water This is used as a control A 0% concentration will be used as a control to see if calcium carbonate would react with water or not. This would then make sure that the reaction only takes place if HCL is present. Prediction: The higher the concentration, the faster the reaction will occur. From background knowledge, it is known that a reaction will occur when particles collide, so the more particles there are the more collisions there will be. If there are more reactant particles per set volume higher concentration more collisions will occur per second, consequently, more particles reacting per second and the rate of reaction is increased. So for a lower concentration there will be less particles, so there will be less collisions therefore the reaction will be slower. Also the higher the concentration the more gas will be produced. This is because if there's more particles higher concentration reacting with the solid marble chips then the reaction will take place quicker. Consequently, the lower the concentration, the less particles to collide and start a reaction so less gas is produced. Equipment: · HCL · Water · Marble chips · Pessel and mortar · Stopwatch · Weighing scales correct to 2d.p. · Spatula · Water trough · Measuring cylinder x2 · Boiling tube with bung and pipe · Clamp stands x2 Method: To measure the rate of reaction, time how long it takes for the marble chips to react and measure the gas given off. To do this put a 100cm3 measuring cylinder in a water trough, with water inside it, held up by a clamp stand. Then put the pipe from the boiling tube under the measuring cylinder. The boiling tube with a pipe will be held by another clamp stand opposite the measuring cylinder. Crush the marble chips into powder with a pessel and mortar and measure out 0.5g of powder for each experiment with the weighing scales. Then, measure the amount of water and HCL needed with the second measuring cylinder. For each different concentration the exact same thing will be done. Put the HCL/Water solution into the boiling tube and make sure the pipe is under the measuring cylinder. After that pour the calcium carbonate powder into the solution, then start the stop clock and put the bung on the boiling tube the same time the calcium carbonate goes in. Then, every five seconds, measure how much gas has been produced using the scale on the measuring cylinder. Repeat the experiment three times for each different concentration and then take an average. Diagram: Chemistry for you page 190 This diagram is similar to the experiment conducted except a boiling tube held by a clamp stand with a pipe and bung was used instead of a flask. Fair test: · The marble chips are crushed to make sure the surface area is the same for each experiment because a larger surface area would take longer to react than a smaller one. So if all the chips are of the same surface area, then they will all react at the same speed, making it a fair test. · All the HCL will be of the same strength, as all experiments will use the same HCL from the same bottle. Stronger acid will speed up the rate of reaction. · The water and acid will be of the same temperature each time because temperature affects the rate of reaction. · After each experiment, the boiling tube will be cleaned properly to get rid of the acid and bits of Calcium carbonate so there's no extra acid or calcium carbonate in the next experiment. · The 100cm3 measuring cylinder will always be full to the top with water so that measurements will be fair. Safety: · To ensure that no acid gets into anyone's eyes, safety goggles will be worn. · Make other persons aware of harmful chemicals. HCL · Necessary medical equipment near by, e.g. eye wash. · Have a cloth or towel near by to clean up any spilt acid so it isn't hazardous to anyone around. Results: Amount of HCL cm3 Amount of water cm3 Gas produced every 5seconds cm3 Average 1st time 2nd time 3rd time 20 0 25 24 25 24.67 45 44 40 43.00 55 57 53 55.00 61 60 57 59.33 65 68 64 65.67 67 68 66 67.00 68 69 67 68.00 69 69 68 68.67 70 71 69 70.00 70 70 70 70.00 70 70 70 70.00 70 70 70 70.00 15 5 20 19 22 20.33 38 35 40 37.67 44 40 41 41.67 47 44 42 44.33 48 45 45 46.00 51 47 46 48.00 53 50 48 50.33 55 54 49 52.67 57 56 50 54.33 58 57 55 56.67 59 58 58 58.33 61 59 59 59.67 64 60 60 61.33 64 62 63 63.00 65 63 65 64.33 66 65 66 65.67 66 67 70 67.67 66 67 71 68.00 10 10 12 10 13 11.67 26 23 20 23.00 29 25 26 26.67 31 27 27 28.33 32 28 28 29.33 33 28 29 30.00 34 29 32 31.67 35 31 34 33.33 36 32 35 34.33 36 33 37 35.33 37 35 38 36.67 38 36 39 37.67 39 37 39 38.33 39 38 40 39.00 40 38 41 39.67 41 39 41 40.33 41 40 42 41.00 43 40 43 42.00 43 41 44 42.67 44 42 44 43.33 45 43 45 44.33 45 44 45 44.67 45 44 46 45.00 5 15 12 13 11 12.00 20 19 21 20.00 23 24 22 23.00 24 24 25 24.33 25 25 25 25.00 25 25 25 25.00 25 26 26 25.67 0 20 0 0 0 0 All results will be plotted on the same graph. This will then make it easier to analyze my results. The average amount of gas measured cm3 will be plotted against time seconds. Graph to show results: The graph was produced by hand and scanned into the word document. Analysis: All concentrations produced gas rapidly to begin with but the most rapid was the 100% concentration. This happened with all the different concentrations except they all started to increase with a steady rate at different times. 100% 30 seconds 75% 15 seconds 50% 10 seconds 25% 10 seconds From this we can see that the higher the concentration, the faster the reaction starts and the longer it continues rapidly. The graph indicates this in the linear gradient of the slope. As the reaction increases the gradient becomes steeper. This result supports the predictions made based on the collision theory. As there are more particles in a higher concentration, there are more collisions so the reaction is faster. When the graph became flat, it was shown that there was no more solid to react with the HCL saturation. The reactions all varied in how long the reaction took place for. 100% 60 seconds 75% 90 seconds 50% 115 seconds 25% 40 seconds The longest reaction was the 50% concentration. The graph shows this by the line leveling out for longer linear gradient. Although it was the longest reaction it didn't produce the most gas. It just produced gas very slowly as it was a low concentration, because there wasn't enough particles to react to make the reaction faster. So gas was produced but very slowly and not much of it. 100% concentration solution was over quickly again, shown by the line on the graph and produced a lot of gas; due to there being more particles to react with the solid marble chips. The 25% concentration however, took place over an even shorter time than the 100% concentration but a lot less gas was produced in the 25% concentration again, due to there not being many particles. The different concentrations also varied on how much gas was produced overall on average. 100% 70.00 cm3 75% 68.00 cm3 50% 45.00 cm3 25% 25.67 cm3 As predicted, the most gas was produced by the higher concentration and the least gas was produced by the lowest concentration. From the graph it can be seen that for different concentrations the amount of gas produced varies. This is due to there being more particles in a higher concentration to react with the solid marble chips. The results gained support the theory that the more concentration, the faster the reaction and the more gas is produced. This matches the predictions made. It is also seen that as the concentrations become less, gas is produced at a much slower, yet at a steady rate because of not having enough particles to react with the substance making the reaction slower. The conclusions and prediction are all based on the collision theory: All particles have to collide in order to react with one another. Evaluation: The method used for conducting the experiment was an effective one as: · It was easily done over the amount of time given in class to conduct the experiment. · It was simple and easy to repeat a lot of times to get enough results to calculate averages. · Produced sufficient results and were easy to present on a graph to compare. · It was a safe experiment. · It was an easy experiment to make sure everything was a fair test and accurate. If the investigation was to be done again, consideration may be given to repeating the test a few more times for each concentration to produce a better average. From the graph it can be seen that some of the concentrations don't level out. This is because for each concentration, each time the experiment was conducted; the gas stopped being produced at different times. So when the average was taken it didn't always show the gas had stopped being produced. So the graph doesn't always level off. Maybe if the gas produced every 5 seconds had been recorded more times, say 10 or 20, instead of 3, the graph would've leveled off. Another reason for this is maybe that the experiment wasn't left going for long enough and a few more bubbles of gas could've been recorded giving more accurate results. It is shown on the graph that the 50% concentration produced more than the 75% most probably because of the reason just mentioned. Even though the results weren't as accurate as they could've been for the reasons mentioned above, they still verified the predictions and conclusions made. Further experiments could be conducted to extend the work I have done. These could be to investigate the other variables in the same way I have conducted my experiment: · Surface area "“ different sizes of marble chips for each experiment. · Temperature of the acid "“ investigate a range of temperatures. · Catalysts "“ investigate the effect of a catalyst in an experiment. If then all these different factors were investigated, all the results could be put together to prove the conclusions further. Bibliography: Books: 1. Chemistry For You, National Curriculum Edition for GCSE "“ Lawrie Ryan Page 190 "“ diagram of experiment 2. Revision Guide for GCSE Double Science, Chemistry, Higher level "“ Richard Parsons Page 79 "“ diagrams to show how different variables affect the rate of reaction Page 80 "“ Graph to show the effect of a catalyst on the rate of reaction Websites: 1. http://www.revisioncentral.co.uk 2. http://www3.mistral.co.uk/cns/depts/science/sc1/GCSE/   

Aim: To investigate the rate of reaction between Hydrochloric acid and marble chips. Background Knowledge: Factors that affect the rate of reaction between hydrochloric acid and marble chips or any other reaction are called variables. They are: ¨ The surface area of the chips...

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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...

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