[bugsmenot]

I did an experiment investigating how concentration affects the rate of reaction between sodium thiosulphate and hydrochloric acid.

I worked out the orders to give the following equation to work out the rate constant:

rate constant = rate / [ sodium thiosulphate] [ hydrochloric acid ]

(where rate = 1/time taken)


In the experiment I changed the concentration of sodium thiosulphate while keeping hydrochloric acid the same, and changed the concentration of hydrochloric acid while keeping the concentration of sodium thiosulphate the same.

The problem is this gave me two rate constants. So what would the rate constant 'k' be in the following equation?

rate = k [Sodium Thiosulphate] [ Hydrochloric Acid]

The values of both rate constants I got when rounded were 0.18. So does k = 0.18? I'm just confused because I worked out two rate constants (one for sodium thiosulphate and one for hydrochloric acid)

[Donaldson Tan]

1. have u determined/confirm the reaction rate is 1st order with respect to HCl and Thiosulphate concentration?

2. the rate constants you get from different sets of experiment data should arrive at roughly the same value.

[bugsmenot]

Ok thanks I figured it out now, thanks for your help

[mass]

why is it necessary to measure rate constants?