JEE MAIN - Chemistry (2008 - No. 11)
Amount of oxalic acid present in a solution can be determined by its titration with $$KMn{O_4}$$ solution in the presence of $${H_2}S{O_4}.$$ The titration gives unsatisfactory result when carried out in the presence of $$HCl,$$ because $$HCl$$ :
gets oxidised by oxalic acid to chlorine
furnishes $${H^ + }$$ ions in addition to those from oxalic acid
reduces permanganate to $$M{n^{2 + }}$$
oxaidises oxalic acid to carbon doxide and water
Explanation
The titration of oxalic acid with $$KMnO{}_4$$ in presence of $$HCl$$ gives unsatisfactory result because of the fact that $$KMn{O_4}$$ can also oxidise $$HCl$$ along with oxalic acid. $$HCl$$ on oxidation gives $$C{l_2}$$ and $$HCl$$ reduces $$KMnO{}_4$$ to $$M{n^{2 + }}$$ thus the correct answer is $$(c).$$
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