The Relationship Between Reaction Rate and Concentration

The Relationship Between Reaction Rate and Concentration

I am going to investigate how varying the concentration of Sodium

thiosulphate solution affects the rate of reaction with Hydrochloric

Acid.

The equation for the reaction is:

[IMAGE]Sodium thiosulphate + Hydrochloric Acid Sodium

Chloride + Water + Sulphur + Sulphur dioxide

[IMAGE]Na2S2O3(aq) + 2HCl(aq)

2NaCl(aq) + H2O(l) + S(s) + SO2(aq)

This reaction has a definite end (when the cross on the test tube

'disappears'). The faster the cross 'disappears' the faster the

reaction and by timing how long this takes, we can establish the rate

of reaction.

I predict that the greater the concentration of Sodium thiosulphate

solution in the experiment, the faster the chemical reaction will take

place. Therefore, the cross will disappear more quickly due to the

cloudiness of the solution, but only up to a certain temperature

point. After this, the solution will not react within a reasonable

time because the solution will begin to decompose.

I think that the concentration of a solution affects the rate of

reaction because the rate of reaction depends on how frequently the

molecules of the reacting substances collide. A more concentrated

substance has more molecules for a given volume than a more dilute

substance. Because there are more molecules about, the frequency of

successful collisions is greater, and the reactions happen faster.

Prediction

I predict that when I add more water to the sodium thiosulphate

solution, the time it takes for the cross to disappear will lengthen.

I predict this because, for particles to react they must collide with

each other. If there is a higher concentration of sodium thiosulphate

particles in a given volume there, is a higher chance of the particles