Rate of Reaction Investigation

Rate of Reaction Investigation

Aim:

To investigate the effect of concentration upon the rate of reaction

between Sodium thiosulphate (Na²S²O³) and dilute Hydrochloric acid

(HCl). This is:

Na²S²O³ + HCl 2NaCl + H²O + SO² + S

This experiment will be done in two parts. Firstly the experiment will

be done with the volume of HCl and total volume constant, and changing

the Thiosulphate and water volumes, thereby changing the concentration

of the thiosulphate. The second part of the experiment will be keeping

the thiosulphate and total volume constant and changing the HCl and

water volumes. The indicator for the rate of reaction is the sulphur

deposit left by the reaction, and when it covers a cross on a piece of

paper, the timing is stopped.

Theory:

I believe that the weaker the concentration of the thiosulphate, the

slower the rate of reaction. This is because of collision theory. In

collision theory there are three main things that affect the collision

of atoms in a reaction and thus the rate of reaction, temperature of

reagents, surface area of reagents and the concentration of the

reagents. For concentration (which is the part which is being

investigated) it says that the higher the concentration of the

reagents, the quicker the rate of reaction. I also believe that the

weaker the acid concentration, the slower the rate of reaction. This

is also because of collision theory. I also believe that changing the

concentration of the thiosulphate will have more of an effect on the

reaction time, as this is the reagent that reacts to give the sulphur

used for indicating the reaction time.

Method:

1) Set up apparatus as in diagram. (Note protective goggles must be

worn at all times)

2) Add 10cm³ of Na²S²O³ and 40cm³ of water. (Measured by measuring

cylinder)

3) Add 10cm³ of HCl and start timing the reaction. When the deposits

cover the cross, stop timing.

4) Repeat experiment with other values for Na²S²O³ and water, keeping