Which of the following is a redox reaction?

Fluorine reacts with ice and results in the change:
$H_2O_{(s)} + F_{2(g)} \rightarrow HF_{(g)} + HOF_{(g)}$
Justify that this reaction is a redox reaction.

The number of moles of acidified $KMnO_4$ required to convert one mole of sulphite ion into sulphate ion is

Explain the balancing of a redox reaction by the oxidation number method.

Consider a titration of potassium dichromate solution with acidified Mohr's salt solution using diphenylamine as indicator. The number of moles of Mohr's salt required per mole of dichromate is

Assertion: Change in color of acidic solution of potassium dichromate by breath is used to test drunk drivers.
Reason: Change in color is due to the complexation of alcohol with potassium dichromate.