7.1.2 Average Rate of Reaction – Immeasurable Quantities
Finding Average Rate of Reaction from Immeasurable Quantities
- In some reaction, some changes are observable but difficult to be measured. For example
- Change in colour
- Precipitation
- The time taken for the colour of a reactant to change or certain amount of precipitate to form can be used to measure the rate of reaction.
- If the quantity change is immeasurable
Example
When the aqueous of ethanadioic is mixed with acided potassium manganate(VII) , the reaction happen slowly at room temperature. The purple colour of the solution is bleached after 20 seconds. Calculate the average rate of reaction.
Answer
Rate of reaction
= 1/time
= 1/25
=0.04 s-1
Example
2HCl(aq) + Na2S2O3(aq)
→2NaCl(aq) + S(s) + SO2(g) + H2O(l)
In a reaction between dilute hydrochloric acid and sodium thiosulphate, sulphur precipitate was produced after 2 minutes. Find the average rate of the reaction?
Answer
