Investigating the Changes in Reaction When Sodium Thiosulphate is Added to Dilute Hydrochloric Acid

Investigating the Changes in Reaction When Sodium Thiosulphate is Added to Dilute Hydrochloric Acid

Concentration

Aim:

To observe the changes in reaction when sodium thiosulphate is added

to dilute hydrochloric acid.

Prediction:

I predict that the higher the concentration of hydrochloric acid is

the faster the reaction will take place.

Scientific knowledge:

When the concentration of hydrochloric acid is high the reaction will

take place faster. This is because in a high concentration of

hydrochloric acid there are more particles so collisions will occur

more frequently. The more collisions there are, the faster the

particles will react. If there was a lower concentration of sodium

thiosulphate the particles will not collide as often as they would in

a high concentration so the reaction will take place slower. This is

why a graph of results may look like this:

Effect of Changing

Concentration

[IMAGE]

The temperature of the solution will effect the rate of reaction. This

is because the higher the temperature is the more energy the particles

will have, with the particles moving faster they will be colliding

faster than a colder solution, thus increasing the speed of the

reaction. A larger surface area will also speed up the reaction time.

This is because with a larger surface area the more particles there

will be to collide with each other. This therefore will be faster than

using a smaller surface area. Lastly a catalyst would increase the

speed of the reaction as it reacts with the elements in the solution

without being used up itself.

Equation for experiment:

[IMAGE]Sodium thiosulphate + hydrochloric acid sodium chloride +

sulphur + sulphur dioxide

[IMAGE]Na S O (aq) + 2HCl (aq) 2NaCl (aq) + S (s) + So (g)

+ Water

H O (l)

Effect of Changing

Concentration

Key variables: These are the factors I could vary:

* Temperature

* Concentration

* Surface area

* Use of a catalyst