In the dehydration of oxalic acid by conc `H_(2)SO_(4)`
`(COOH)_(2) rarr CO + CO_(2) + H_(2)O`
`2 mL` of the solution was withdraw at different times and titrated against `0.1 N K MnO_(4)` solution. Show that the reaction is of first order.
`|{:("Time (mins)",0,300,450,600),("Vol of" KMnO_(4) "used (mL)",22.0,17.0,15.0,13.4):}|`
Note: This is an example of indirect estimation of reactant, i.e., titrating of oxalic acid by `KMnO_(4)`.

Explanation

`(COOH)_(2) rarr CO + CO_(2) + H_(2)O`
`k = (2.303)/(t)log.(V_(0))/(V_(t))`
(a) `k = (2.303)/(300)log.(22)/(17)`
`= (2.303 xx 0.119)/(300) = 0.00085 min^(-1)`
(b) `k = (2.303)/(450)log.(22)/(15) = 0.00085 min^(-1)`
(c ) `k = (2.303)/(600) log.(22)/(13.4) = 0.00085 min^(-1)`
The value of `k` constant. Hence, first order reaction.