Chemistry Coursework

Essay by pmagur01High School, 11th gradeA, November 2004

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The Effect of Concentration on the Rate of Reaction between Hydrochloric Acid and Sodium Thiosulphate


In this experiment we are going to react Hydrochloric Acid with Sodium Thiosulphate. We are going to see what effect the concentration of Hydrochloric Acid has on the rate of reaction. We are going to keep the concentration of the Sodium Thiosulphate constant. We are going to vary the concentration of the Hydrochloric acid. The total volumes of the two solutions will remain constant therefore keeping the overall volume constant.

Na2S2O3 + 2Hcl S + SO2 + 2NaCl + H2O

Scientific Knowledge

Particles, such as molecules, atoms or ions, must collide before a chemical reaction can take place. This diagram shows this:

So the increase in concentration means increase in rate of reaction. If you doubled the concentration you would also double the amount of the product that is produced.

This is explained in our textbook Longmans GCSE chemistry:

"If you increase the concentration of the reactants, the reaction becomes faster.

Increasing the concentration increases the chances of particles hitting each other"


As the concentration increases the rate of reaction increases because of the scientific knowledge shown above.


· Lab coats are to be warn as spillages may occur

· Safety glasses must be worn as we are using acid

· If any glass is broken tell the teacher immediately

· Wipe up any spillages and then wash your hands.

Preliminary Work

We are going to have to do some preliminary work so that we can decide what ranges we are going to do and if there is anything we can do to improve the method to make it more accurate.

Preliminary Method

1. Measure out the Sodium Thiosulphate using a measuring cylinder.

2. Measure out and then dilute the Hydrochloric...