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How Does Changing the Concentration of a Substance Affect the Rate of Reaction?

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Introduction

How Does Changing the Concentration of a Substance Affect the Rate of Reaction? Introduction Rates of reactions are affected by four factors. The four factors are the concentration of the acid used, the surface area of the reactant, the temperature of the acid and whether a catalyst is used or not. I have chosen to investigate the concentration of the acid used to dissolve calcium carbonate. The reason I have chosen to investigate this is because there is not a known catalyst for calcium carbonate, so this would be a hopeless experiment, and a waste of time. Also, changing the surface area of the reactant would pose too difficult as it is difficult to change the surface area and at the same time keeping the mass the same. I chose not to change the temperature of the acid because it is too difficult to maintain a constant temperature. For example, if a water bath is used, before the acid came out of the water bath the temperature of the acid could be 80�C, however by the time the reactant is added to it, the temperature may have dropped. This would make it an unfair test. When Hydrochloric acid and Calcium Carbonate are mixed together, they make Carbon Dioxide, water and Calcium Chloride. This is shown in a formula as like this: Hydrochloric acid + Calcium Carbonate (HCl) (CaCO3 ) Carbon Dioxide + Water + Calcium Chloride (CO2 ) (H2O) (CaCl2) Prediction I think that the stronger the acid the faster the rate of reaction will be. ...read more.

Middle

4. Put the delivery tube under the measuring cylinder in the beaker. 5. Add 1g of Calcium Carbonate marble chips to the Hydrochloric acid in the conical flask, and immediately afterwards put the bung from the delivery tube into the conical flask, and start the timer, to trap any gas given off. 6. Time for one minute, and record the volume of gas collected in the measuring cylinder every 10 seconds. Once the one minute mark is reached, remove the bung from the conical flask and then record how much gas was collected in the measuring cylinder. 7. Repeat this twice with the same concentration of Hydrochloric acid. 8. Repeat this whole experiment with another 4 different concentrations of Hydrochloric acid. Diagram of Equipment Safety To make sure my experiment is safe, I will wear goggles to protect my eyes from the Hydrochloric acid and keep all bags and stools under tables to prevent me from tripping and falling with acid. I will mop up any spills straight away to stop me from slipping over, which could prove dangerous if I was carrying acid. Preliminary Findings Primarily, I had decided to dissolve 3g of Calcium Carbonate marble chips in 50ml of hydrochloric acid for 5 minutes. However, all of the marble chips had dissolved before the 5 minutes. As a result of this I decided to time for a shorter amount of time. I decided to time for 1 minute. However, the marble chips still dissolved too fast so I decided to, instead of shortening the length of time, use a smaller amount of marble chips. ...read more.

Conclusion

When using the 1.5M concentration of Hydrochloric acid, after ten seconds the volume of gas produced was 0cm�. This did not fit on the line of best fit for the 1.5M concentration, and to have fit on the line of best fit it would have had to have produced approximately 1.3cm� of gas. This anomaly could have happened because the temperature in the room could have changed and not stayed at a constant temperature. Also, the surface area may have affected how the experiment substance reacted. The second anomaly was when I used the 2.0M concentration of Hydrochloric acid. After 60 seconds, the volume of gas produced was 14.3cm�. This appeared to be too high to fit on the line of best fit. The reason for this anomaly will be the same reasons as for the first anomaly. The method I used was fairly reliable; however, a few improvements could have been made such as controlling the variables. To keep the surface area the same, a special cutter could have been used to cut the Calcium Chloride marble chips into equal size and shape. This would have kept the surface area the same. Also, a temperature controlled environment would have controlled the temperature variable. These two improvements would have kept the experiment a fair test. Another improvement would be to use a set of scales that were more accurate than to 0.1g. This would ensure that each Calcium Carbonate marble chip was exactly 1g, but because I used a set of scales that were only accurate to 1g, the marble chips I used may have been slightly under or slightly over 1g. This would have affected my experiment. ?? ?? ?? ?? ...read more.

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