How Does Temperature Affect the Rate of Reaction Between Hydrochloric Acid and Sodium Thiosulphate

Authors Avatar

Investigating How Temperature Affects The Rate Of Reaction Between Hydrochloric Acid and Sodium Thiosulphate

Aim: To investigate how temperature affects rate of reaction between hydrochloric acid and sodium thiosulphate.

Background Info

When sodium thiosulphate reacts with hydrochloric acid (or any acid) it forms a yellow precipitate. This is sulphur, as shown in this equation:

Na2S2O3(aq) + 2HCl(aq) ---> 2NaCl(aq) + SO2(g) + H2O(l) + S(s)

Sodium thiosulphate + hydrochloric acid --> sodium chloride + sulphur dioxide + water + sulphur

The sulphur precipitate, when the beaker is placed over a cross, will obscure the cross and by timing how long this takes we can time the rate of reaction.

It should work out that the higher the temperature, the faster the rate of reaction. This is because higher temperatures give particles more energy so they move around more, and in turn this means that there are more collisions per second. When particles collide, they react with each other so more collisions means a faster reaction. This is called collision theory.

Activation energy is the minimum energy needed to start a reaction. If particles collide with less than the activation energy, no reaction will occur. It can be thought of as a barrier to the reaction. Various things increase energy and break this barrier so that reaction can take place. Shaking the mixture (in a conical flask) is one of time, because it makes particles collide more frequently and more violently. Higher temperature is another, because it gives particles more energy and they move more, so collide more frequently.

Prediction

Based on my background information, I predict that with every 10ºC increase in temperature, they time taken to obscure the cross will decrease by 4 seconds.

Preliminary Work

To find the most accurate way of recording results we conducted preliminary tests. We varied the amount of sodium thiosulphate compared to hydrochloric acid, but kept the total volume of the mixture at 60cm3. We went up in steps of 5cm3 along the hydrochloric acid column, and down in steps of 5cm3 along the sodium thiosulphate column.

 

Because test 4 gave the slowest reaction, I decided to use this combination - 35cm3 of hydrochloric acid and 25cm3 sodium thiosulphate. This is because if a reaction takes longer, it leaves more time to think and press the timer at just the right time.

Join now!

Plan

Temperature is the only variable in this reaction, as the aim is to look at the effect of temperature on rate of reaction. All other factors will need to stay constant, including volume of reactants, method of heating up, equipment used, amount of time the mixture is shaken for, and when the cross can be said to be obscured. Here is a step by step plan, taking into account issues of reliability and accuracy.

1. Measure out 35cm3 of hydrochloric acid using a measuring cylinder into a conical flask first. The volumes of the reactants were ...

This is a preview of the whole essay