The average molecular weight of the air which has $21 \%$ of $\mathrm{O}_2$ and $79 \%$ of $\mathrm{N}_2$, is

The number of significant figures in 2.0400 is

Identify the values of $a, b, c, d$ and $e$ for the following unbalanced reaction,

$$ \begin{aligned} a \mathrm{KNO}_3+5 \mathrm{C}_{12} \mathrm{H}_{22} \mathrm{O}_{11} \longrightarrow b \mathrm{~N}_2 & +c \mathrm{CO}_2 +d \mathrm{H}_2 \mathrm{O}+e \mathrm{~K}_2 \mathrm{CO}_3 \end{aligned} $$

Calculate the number of moles of NaOH required to completely neutralise 100 g of $118 \%$ oleum.