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Investigating the effect of concentration on the rate of reaction Skill(s) assessed: Topic C10 [Experiment 9 (in S4)] Investigating the factors affecting the rate of reaction IGCSE Coursework Skills C2, C3, & C4 Some of the factors affecting the rate of a reaction that you have studied are: Temperature Concentration Surface area Aim: Investigating the effect of changing the concentration on the reaction between calcium carbonate and hydrochloric acid, by collecting the carbon dioxide gas given off.
CaCO3(s) + 2HCl(aq) –> CaCl2(aq) + H2O(l) + CO2(g) Hypothesis: My hypothesis is that as we increase the concentration of the HCl, the rate of the reaction will be faster; this is because more collisions will be present Materials: – Small calcium carbonate chips – Dilute hydrochloric acid (1 moldm-3) – Distilled water – Delivery tube – Bowl – Conical flask (100ml) – Beaker – Measuring cylinder (100 cm3) – Stop watch – Balance – Clamp – Clamp holder – Safety Glasses.
Method: 1. Collect all materials 2. Fill the bowl and the 100 cm3 cylinder with water 3. Holding the end so that the water doesn’t go out, turn the cylinder upside down and place it down the bowl, keeping it still with the clamp, put the delivery tube at the hole of the cylinder 4. Weight 3g of small size calcium carbonate chips 5. Put on your safety glasses 6. Add the 3g of small carbonate chips into the conical flask 7. Add the HCl acid in the conical flask 8.
Quickly afterwards put a cork so that you shut all air entries in the conical flask 9. At the same time as you place the cork, start timing how much it takes to get 50cm3 of gas 10. Repeat this experiment using different concentrations of HCl acid by diluting the acid with distilled water, to make it a fair test use always the same amount of chips and always reach 25cm3 in the measuring cylinder so that only concentration and not amount will affect the rate of reaction.
11. Record your results in a neat and tidy table Results: Table: Volume of 1. 0 mol dm^-3 HCl (cm^3) Volume of H2O (cm^3) Concentration of HCl (mol dm^-3) Time (s) to reach 50ml Time to reach 100ml Graph: Anomalous Results: In this experiment we were lucky to find no anomalous results at all, everything went on as we planned it was going to go like. Conclusion:
As you can see in the graph, our hypothesis was right, as we increased the concentration of the HCl acid in out experiment, more collision were happening and therefore the time for it to reach 50ml was becoming smaller and smaller, meaning that the reaction was becoming faster. So we end up with the conclusion; more concentration of acid = faster rate of reactions = more collision. We could also see in the trend/pattern that at first, when we started increasing by only 0. 2 in concentration, the time for it to reach 50ml decreased from 38 to 17 seconds, almost half of what it was before!.
After a while, as we increased the concentration, the difference between the two concentrations began to get smaller and smaller, it first started at decreasing from 38s to 17s, then from 17s to 9s, 9s to 7s and from 7 to five seconds. At this last 2 differences, at the change from 0. 6 to 0. 8, and 0. 8 to 1 in mol dm^-3 of concentration of HCl, the difference was in both only of 2s, showing off that if the acid was yet too concentrated, and almost getting to being fully concentrated, the difference in time to reach the 50ml will become smaller and smaller.
Evaluation/Improvement: The experiment was carried out really well, there was no significant anomalous result which indicated that we were doing the right thing, the experiment fulfilled our hypothesis decision, it went on as we planned it would. We should have repeated the experiment, repeating the experiment would have given us much more accurate results, and we have used the same balance for each measuring of calcium carbonate, so that we make it a fair test.