Coursework: rates of reaction, strength of acid

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Coursework: rates of reaction, strength of acid

I have been asked to investigate the speed of reaction of acid acting on marble chips.

Aim

To find out what factors effect the rate of a reaction - the reaction between marble chips and hydrochloric acid.

Key factors

The Quantity of marble chips used , This could increase or decrease the surface area of the marble chips. Speeding up or slowing down the reaction because with a larger surface area more of the marble is reacting with the acid.

The amount of acid used, more or less acid could change the amount of time that the reaction takes. Varying the amount of acid used would alter the time for the reaction because there are more or less acid particles to react with the marble chips. More acid longer time, less acid quicker time.

The strength (concentration) of the acid used, alters the amount of particles of acid in cm3, this means that as the strength increases the amount of particles increase, giving more acid particles to react with the marble chips. Increasing the acid strength will speed up the reaction but taking longer to finish because there are more acid particles to react with the marble chips.

The size of the marble chips, as marble chips increase their size there is less surface area for the acid to react with. The same weight of Marble chips of smaller size will increase the reaction speed.

Prediction

The variable in the experiment that I am going to change is acid Strength.

As the strength increases the amount of particles increase, giving more acid particles to react with the marble chips.

I predict that as the concentration of the acid increases the speed of the reaction will increase, also increasing the amount of gas produced.

Hypothesis

My Hypothesis is that the higher the concentration of acid the faster the reaction will take place, this is because in a higher concentration there will more hydrochloric acid molecules per set volume. This means that there will be a higher chance of the calcium carbonate molecules colliding with the hydrochloric acid and reacting. This should in theory increase the rate of reaction as the concentration is increased.
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The reaction rate, however, should decrease as the experiment progresses because as the reaction time increases the number of hydrochloric acid molecules present will decrease as they have been reacted to form water calcium chloride and carbon dioxide. The additional water and calcium chloride present as the experiment progresses should decrease the rate of reaction because of decrease in acid concentration. The graph of the reaction should be curved as the reaction rate will slow down.

The increase in the acid concentration should be directly proportional to the increase of the reaction rate at a given ...

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