Rate of Reaction Coursework

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An experiment to find the rate of reaction between two liquids

Introduction

This is an experiment to determine the effect of changing the

concentration of sodium thiosluphate (Na S O (aq)) on the rate of

reaction between sodium thiosulphate and hydrochloric acid (HCL (aq)).

HCl+sodium thiosulphatearrowsodium chloride+sulphur

dioxide+sulphur+water.

HCl(aq) + Na2S2O3(aq) arrow NaCl(aq) + SO2(g) + S(s) + H2O(l)

If one were to place hydrochloric acid and sodium thiosulphate into a

beaker a white cloudy solution is left in the beaker. The rate of the

reaction can be controlled by concentrating one of the liquids, or one

could add water to dilute the mixture to slow the reaction.

Method Apparatus

Two beakers of 50cm3

Sodium Thiosulphate

Hydrochloric acid

Conical flask

Measuring tube-10cm3

Measuring tube-50cm3

The apparatus is set up as shown above. I will place 50cm3 of Sodium

Thiosulphate; I will keep Hydrochloric acid at a constant rate of

5cm3. Then I will reduce the sodium thiosulphate and increase the

water, for example:

50cm3: 0cm3

40cm3: 10cm3

30cm3: 20cm3

20cm3: 30cm3

10cm3: 40cm3

When the reaction is complete the solution left should be white and

cloudy, to test this; I will place a piece of paper with a cross on

it. If I cannot see the cross on the paper then the reaction has

finished.

Constants

* Hydrochloric acid

* Temperature

* Length of X on paper

* Room temperature

Variables

· Sodium thiosulphate

· Water

Hydrochloric acid will be kept at a constant rate because the

experiment is about changing the concentration of sodium thiosulphate.

The temperature will be kept constant with a precise thermometer in

the solution. The paper with the X on it will always be the same piece

of paper. The room temperature will be kept constant because I will

make sure the windows are closed.

Sodium thiosulphate will be varied because that is the point of the

experiment. The water will be varied to dilute the reaction.

Scientific explanation

In order for the sodium thiosulphate and Hydrochloric acid to react

their particles must:

* Collide with each other

* The collision must have enough energy

This is shown by the explanation below:

The particles in the liquid If the collision has enough If the

collision move around continually. energy, a reaction takes place does

not have here an acid particle is enough energy about to collide with a

no reaction sodium atom occurs. The acid particle bounces away again.

If there are a lot of collisions then the rate of the reaction is

fast. If there are not many, the rate is low.

The rate of a reaction depends on how many successful collisions there

are in a given unit of time.

There are three main ways of speeding up a reaction:

* Changing the concentration

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