An investigation into how changing one variable influences the rate of reaction between marble chips and dilute hydrochloric acid.

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Craig Smith

10TER

10L

Chemistry coursework

Planning Section

This experiment is an investigation into how changing one variable influences the rate of reaction between marble chips and dilute hydrochloric acid.

When dilute hydrochloric acid reacts with marble chips the following reaction occurs:

CaCO3 + 2HCl = CaCl2 + H2O + CO2

List of variables which could affect the rate.

  • Surface area: The bigger the surface area of the marble chips means that there will be more CaCO3 particles which means there will be a higher rate of reaction because there is a higher possibility of acid particles hitting the marble chips.
  • Temperature: The higher the temperature the bigger the reaction takes will be when the temperature is higher the acid particles have more energy which means they hit the marble chips harder, therefore the reaction takes place faster.
  • Concentration: The higher the concentration of Hydrochloric acid the higher the rate of reaction will be because there are more acid particles, which means there is a higher possibility that there will be collisions between the hydrochloric acid particles and marble chips.

A list of variables which I will attempt to keep the same.

  • Temperature: I will try to keep this constant by having a thermometer in my solution and always checking that it is at room temperature.
  • Surface area: I will try to keep this constant by using the same weight of chips each time and also the same amount of chips each time.

The variable which I have decided to investigate is.

The variable, which I have decided to investigate, is concentration of Hydrochloric acid.


Preliminary work.

In my preliminary work I am going to see whether it is better to use the same marble chips over and over again or using new marble chips each time.

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I will use 5 grams of marble chips and I will use a concentration of 2 Molar.

Results of preliminary work

 

This shows me that it is better to use new chips every time because it is more accurate and the results are closer together. This happened because when I used the same chips over and over again some of the Chips reacted with the acid, which meant the surface area got smaller which meant the reaction took longer but with new chips each time the surface area stays approximately the same which means the ...

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