How does the concentration of acid affect the rate of a reaction with calcium carbonate?

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How does the concentration of acid affect the rate of a reaction with calcium carbonate? 

  Calcium       +     Hydrochloric           Calcium    +  Carbon   +    Water

Carbonate                 Acid                           Chloride       Dioxide

CaCO3 (s)      +        2HCl (aq)            CaCl2 (aq)  +  CO2 (g)     +    H2O (l)

Introduction

        I will be using the reaction between calcium carbonate and hydrochloric acid to see how the concentration of acid affects the rate of a reaction. By doing the above experiment I will prove that the higher the concentration of acid, the faster a reaction will occur. I have carried out a previous experiment called the ‘Disappearing Cross’, in which I used the reaction between thiosulphate, hydrochloric acid and water to see how concentration affects the rate of reaction. When we added the hydrochloric acid to the water and thiosulphate a reaction occurred, causing the water to become foggy so that the cross was no longer visible through the conical flask.

The results for the Disappearing Cross experiment were as follows;

        You can see that when the hydrochloric acid was most dilute the cross took 711 seconds to disappear, and when the acid was most concentrated the cross took just 82 seconds to disappear. This shows that the more dilute the concentration of acid, the slower the rate of reaction and the more concentrated the acid the faster the rate of reaction because when acid is more concentrated there are more molecules, therefore increasing the chance of a successful collision, and speeding up the reaction. This is known as the ‘Collision Theory’. I am now going to do another experiment, using calcium carbonate and hydrochloric acid to see if the same effect is observed with a different reaction.

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Apparatus Needed

  • Gas syringe
  • Retort stand
  • Conical flask
  • Boss and clamp
  • Bung
  • 2x Measuring cylinder
  • Stopwatch
  • Delivery tube
  • Beaker
  • Balance
  • Goggles
  • CaCO3 (Medium sized Calcium Carbonate chips)
  • H2O (Water)
  • HCl (Hydrochloric acid)

Diagram

Below is a diagram showing how apparatus should be set up:

Method

  • Set apparatus up as shown in the diagram above
  • Using the balance, measure 5g of Calcium Carbonate
  • Measure 30cm3 of acid solution
  • Add CaCO3 and the acid solution together in the conical flask and put the bung ...

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