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GCSE CHEMISTRY COURSEWORK: Titrations
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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.

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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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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 ...

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The following shows the collision theory...The following shows the collision theory used to explain the effect of temperature and concentration Prediction: In this investigation I expect to find as I increase the temperature the reaction will take place faster. This is because as the temperature increases, it gives more energy to the sodium thiosulphate and hydrochloric acid particles causing them to collide more often and with more force; this increases the rate of reaction. As the temperature rises, a greater number of sodium thiosulphate and hydrochloric acid particles have energy greater than the activation energy therefore leading to more successful collision, and increasing the rate of reaction. * Plan: I will be mixing the two clear liquids 'Hydrochloric Acid' 1M "“HCl and 'Sodium Thiosulphate Solution' 40G/L - Na2S2O3, in order to observe and analyse the reaction changes if any when I increase the temperature. I will add 50cm of weak sodium thiosulphate and 5cm of hydrochloric acid into the beaker; I will make a quick mix of the solution before beginning to start the clock. I will watch the reaction and try to find out whether the solution goes milky and the cross disappears, this will indicate whether the reaction is done. Once the cross has disappeared in the solution I will stop the clock and record the results. Place Apparatus in middle of desk: Boiling tube, test tube, 600ml beaker, kettle, Distilled water bottle, Sodium Thiosulphate, Hydrochloric Acid, Stop Clock, Paper Cross, 25ml measuring cylinder, 100ml measuring cylinder and 10ml measuring cylinder. I will then draw a cross of any size on a piece of A4 paper Prepare Batch of sodium thiosulphate and distilled water using both a 100ml and 25ml measuring cylinders. Place 10cm of Hydrochloric acid into test tube using 10ml-measuring cylinder. Place 50cm of sodium thiosulphate/distilled water solution into boiling tube using a 25ml-measuring cylinder. Put water in kettle and switch on Place a cross on the outside of the 600ml beaker Place 150ml of cold water into 600ml beaker Mix the hot and cold water in beaker Use Thermometer to take the temperature of the sodium thiosulphate and distilled water and Hydrochloric acid with two thermometers in each test tube Wait for the temperature of both the Solution and Hydrochloric Acid to reach the required temperature Pour Hydrochloric acid into solution and start stop clock immediately Wait until cross disappears because of the cloudy solution, and then stop the stop clock Record the time in table Take the temperature of the mixture and record in table Pour away as soon as possible Wash boiling tube out with cold tap water then rinse with distilled water Take average of the start and finishing temperatures and times Repeat Experiments twice for each temperature to improve reliability or to make them reliable. Plot on graph The temperatures that I will carry out the experiments at 25, 30, 35, 40, 45°c. Fair test: I will be able to make this a fair test by keeping all of the solution the same amounts 50cm of weak sodium thiosulphate and 5cm of dilute hydrochloric acid. I will keep these variables the same: Concentration of 2HCl: Concentration of sodium thiosulphate and Hydrochloric acid "“ The concentration of sodium thiosulphate and hydrochloric acid will be kept the same, as to make it a fair test, because if you change the concentration of one reactant it changes the number of particles making the reaction unfair and not reliable. If you create batches of the reactants you reduce the percentage error of volume measurement and of the concentration. E.g. when you measure 25ml of water from a 25ml measuring cylinder a certain amount of water will stay in the cylinder, Then instead of water it was hydrochloric acid and some was left behind, it would change the total concentration because the number of particles has been reduced therefore there is less particles for the other reactant to collide with, also the chance of the amount left behind being the same will be small Volume of Na2S2O3: If I don't keep this constant then it'll effect the reation. Volume of 2HCl: if I don't keep this constant then it'll effect the reation. Temeperature of solution: If I don't keep this constant then it'll increase the energy of the particlesand also increase the chance of a successful collision. I will use the same cross for the whole experiment, also time it accurately and make sure my equipment is working. Equipment: Diagram *Sodium thiosulphate Hydrochloric acid Distilled water 2 Beakers Cross of A4 paper Burette Stopwatch Goggles Funnel Thermometer Water bath To follow this reaction you can measure how long it takes for a certain amount of sulphur to form. You do this by observing the reaction down through a conical flask, viewing a black cross on white paper see diagram below. The X is eventually obscured by the sulphur precipitate and the time noted. By using the same flask and paper X you can obtain a relative measure of the speed of the reaction in forming the same amount of sulphur. Mixè *èOngoing*èWatch stopped* Here is the preliminary result: * Safety: I will make the experiment safe by wearing goggles while handling the irritants and when the reactions are occurring during the experiment. Sulphur and sulphur dioxide are given off during the reactions and are irritants, if breathed in it is dangerous. To avoid this occurring I will keep the room well ventilated by opening windows so the gas can disappear. Each try I do I wash out the beaker several times before starting the experiment. I will make sure the hydrochloric acid does not get in contact with my hands. Analysis: The experiment shows, that when the hydrochloric acid is added to the sodium thiosulphate, a cloudy precipitate appeared. It also shows that when you increase the temperature at which a reaction is taking place, the particles move more quickly resulting in a faster reaction. This has two effects: 1 More collisions take place 2 When a collision occurs, there is more chance that the collision will lead to a reaction, because the amount of energy is more likely to be greater than the minimum amount of energy needed the activation energy Raising the temperature makes the particles move faster. This means that the particles collide more frequently with each other and the rate of the reaction increases. Also, the faster the particles are travelling, the greater is the proportion of them which will have the required activation energy for the reaction to occur. Refer back to prediction diagram HCl+sodium thiosulphatesodium chloride+sulphur dioxide+sulphur+water. HClaq + Na2S2O3aq NaClaq + SO2g + Ss + H2Ol Evaluation: I believe that my results, in general, were very much accurate as I repeated my experiment twice to be able to get an average time taken for the reaction to take place. Providentially, I had no anomalous results which proved the precision and accuracy of my experiment. The method did show the relationship between the temperature and the rate of the reaction. The line graph proves my hypothesis to be correct, but also provides me with some additional information. I have marked on the exact points of the average rate of reaction for every 5 ºC, you can see that at temp 30ºC the speed of reaction did not fall on the line of best fit. This was because the temperature was increased from the previous temp of 25ºC. At 25ºC, the particles would be moving quickly, but not as quickly as they are 30ºC, because as the temperature is increased the particles started moving more quickly and more frequently colliding with more energy so that a faster reaction occurred. Drawing in a line of best fit onto my graph, made it easier to get a more accurate picture from the results. My line graph showed positive correlation meaning that as the temperature was increased the rate of reaction increases. It's also a curve, levelling off gradually. For my Experiment, by having a 5°c rise in temperature allows the number of particles that have energy greater than the Ea Activation Energy 5.45times larger than the number before. This tells me that for this reaction the rate of reaction is almost double for a 5°c rise, therefore shows that the variables were controlled to a sufficient degree of accuracy to allow the reaction to take place at an optimum rate. The experiment was fair and reliable. However, to collect results that are far more accurate, I could have used a mechanical stirrer to act as a catalyst for speeding up the rate of reaction. This would become more precise and dependable. Another factor that we could have improved is the repetitions of experiments; I could have completed the test a further one more time to give me a more adequate average of my results. It was difficult to be able to get both the substances to the required temperature at the same time due to many human errors that can occur. Overall, from my investigation, I believe that the data provides sufficient evidence to support my collision theory as when I increased the temperature the rate of reaction increased. This has turned out to be a successful experiment.   

The following shows the collision theory used to explain the effect of temperature and concentration Prediction: In this investigation I expect to find as I increase the temperature the reaction will take place faster. This is because as the temperature increases, it gives more energy to the sodium thiosulphate and...

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