An investigation into what affects the rate of reaction between Sodium Thiosulphate and Hydrochloric Acid

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Daniel John Constable (8041)

An investigation into what affects the rate of reaction between Sodium

Thiosulphate and Hydrochloric Acid

Investigation to find out how the rate of reaction between sodium

thiosulphate and hydrochloric acid is affected by changing the

concentration.

Introduction

In this experiment I am going to find out how the rate of reaction

between sodium thiosulphate and hydrochloric acid is affected by

changing the concentration.

We place the reaction mixture on a paper with a black cross-drawn on

it. When the cross is completely hidden, the reaction will have

finished. The time taken for this to happen is the measure of the rate

of reaction. We must do this several times, and change the

concentration of sodium thiosulphate, in order for us to determine if

it is a safe test.

The rate of reaction is a measure of the `change', which

happens during a reaction in a single unit of time. The things that

affect the rate of reaction are as follows:

· Surface area of the reactants

· Concentration of the reactants

· The temperature at which the reaction is carried out

· Light

· Use of a catalyst

The factor which we are using is Concentration of the reactants.

Plan

Apparatus

· Conical flask

· Sodium thiosulphate (different concentrations)

· Hydrochloric acid (same concentration each time)

· Water (different concentrations)

· Stop watch

· Paper with black cross on it

· Small memiscus'

· A large memiscus

Method

Firstly, we drew a black cross on a white piece of paper. Then, we put

10 cm³ of hydrochloric acid in a conical flask (measuring the HCL with

a small memiscus), and then put the conical flask on the black cross
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on the paper. We then added 50 cm³ of sodium thiosulphate to the

hydrochloric acid, and at this time we do not need to add any water.

Then, we started the stopwatch.

We waited for the black cross to be completely hidden by the

mixture. When this happened we stopped the stopwatch. By this time the

mixture was completely clouded. Then we recorded what the time was.

We then emptied out the contents of the conical flask, and

cleaned it out, and dried it. Next, we added 45 cm³ of sodium
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