# Investigating The Rate Of Reaction Between Sodium Thiosulphate And Hydrochloric Acid

Investigating The Rate Of Reaction Between Sodium Thiosulphate And Hydrochloric Acid

In this coursework I am going to be investigating the rate of reaction between sodium thiosulphate and hydrochloric acid. The rate of reaction can be changed by theses 4 factors:

1. Temperature
2. Concentration
3. Catalyst
4. Surface area

For this course work I have decided to find out how concentration affects the rate of reaction between Sodium Thiosulphate and Hydrochloric Acid. The equation for this reaction is:

Sodium Thiosulphate + Hydrochloric Acid    Sodium Chloride + Sulphur + Sulphur Dioxide + Water

Na2S203(aq) + 2HCL (aq)   2NaCl(aq) + S(s) + SO2(g) + H2O(l)

When Sodium Thiosulphate and Hydrochloric Acid are mixed together, the solution turns from a colourless solution to a cloudy colour gradually change again into a yellow colour solution (This is called Sulphur). Because the solution turns from a colourless liquid to a cloudy colour solution we could use this information to show how concentration affects the rate of reaction. This experiment I am going to carry out is both simple and safe. I will be carrying out this experiment in the school laboratory because of the space and the equipment I will need is widely available.

In order for my experiment to be fair I will make sure that the measuring cylinders for the Hydrochloric Acid and Thiosulphate will not be mixed up, after each experiment the measuring cylinders, flasks will be rinsed and dried ready for the next experiment. The concentration of either Sodium Thiosulphate or Hydrochloric acid can be changed, I have chosen to change the concentration of the Hydrochloric Acid, I will change the concentration by adding the correct amount of water. I have decided to use a range of 5 different concentrations of Hydrochloric Acid 50-0cm3 going down in steps of 10. To change the concentration I am going to add water 0-50cm3 going up in steps of 10. The amount of Sodium Thiosulphate will be fixed at 10cm3. When doing the experiment I will not stir or move the Chomical flask as this will speed up the rate of reaction by creating more collisions with particles. I will use the same paper with the black cross for all my experiments I will repeat my experiment for each concentration three times as this will make my results more reliable.

## Prediction And Theory Why

I predict that the higher the concentration the quicker the reaction will be. The collision theory says Particles are always moving around, in order for a reaction to occur, the particles have to collide with enough force. If there is not enough energy it will only make the particles bounce off each other. If solutions of reacting particles are made more concentrated there are more particles per unit volume. Collisions between reacting particles are therefore more likely to occur.

...

#### Here's what a teacher thought of this essay

This is a good piece of work, with an excellent risk assessment, and shows a good use of data to support the conclusion.