The rate of reaction of sodium thiosulphate and hydrochloric acid

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Chemistry Coursework

Problem

How do we measure the rate of reaction of sodium thiosulphate and hydrochloric acid, and how does the rate of reaction change as the independent variable is changed.

I have listed below some of the factors and variables, which I think, can affect the aforesaid problem above.

The temperature of the hydrochloric acid.

2 The concentration of the hydrochloric acid.

Factors/Variables to be investigated.

I have decided to choose how the temperature of the hydrochloric acid will affect its reaction rate with sodium thiosulphate. I decided to choose this because I think that our results would be more precise than if we were investigating the effect of concentration on the rate of reaction with sodium thiosulphate. This is because if we had chosen to do concentration, it would have been very difficult to make sure that we were measuring the correct volume of water to decrease the concentration of the acid. We would have had to have used precision equipment such as burettes, which would have been rather time consuming in the limited amount of time that we have allocated to us.

Independent Variable

I am going to investigate how the temperature of the hydrochloric acid will affect its rate of reaction with sodium thiosulphate.

Dependant Variable

I am going to measure the rate of reaction between sodium thiosulphate and hydrochloric acid.= it takes for the cross to disappear.

Controlled Variables

1 The cross-drawn on paper that we use to see how long it takes for it to disappear when the Hydrochloric acid is added to the Sodium Thiosulphate.

2 The room temperature

3 If we have to carry on our experiment to the next day,

We will try and use the same apparatus that we had used the day before to ensure a fair test.

4 The volume of Hydrochloric acid.

5 The volume of Sodium Thiosulphate.

Prediction

I predict that as we raise the temperature of the acid, the reaction will speed up. This is from experience from past experiments and the collision theory. I also predict that when we raise the temperature of the acid, the rate of reaction will increase. I also predict that as the temperature increases by 10 , the rate approximately doubles. I have conducted an experiment earlier, in which I studied the effect of temperature on the rate of reaction of magnesium and hydrochloric acid. Here is the equation below.

Mg + 2HCl ==> MgCl + H

I found that as we raised the temperature, the time taken for the reaction to take place decreased.

Time (secs)

88

72

36

24

Temp ( )

20

30

40

50

Rate

0.0114

0.0139

0.0278

0.0417

As we can see from the table, as we increase the temperature of the acid, the rate of reaction increases. We know when the reaction is finished because the mixture is cloudy and yellow.
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In order to explain this we must look at the collision theory. In order for the magnesium and acid particles to react together,

They must collide with each other.

2 The collision must have enough energy.

This is shown by the drawings below.

The rate of the reaction depends on how many successful collisions there are in a given unit of time. We must also remember that the more successful collisions there are, the faster the reaction. At low temperatures, particles of reacting substances do not have much energy. However, when the ...

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