How many gram-equivalents of $NaOH$ are required to neutralize $25 \ cm^{3}$ of a decinormal $HCl$ solution?

The solution of sulphuric acid contains $80\%$ by weight $H_2SO_4$. The specific gravity of this solution is $1.71$. Its normality is about:

$20 \ mL$ of methane is completely burnt using $50 \ mL$ of oxygen. The volume of the gas left after cooling to room temperature is (in $mL$)

What mass of $95 \%$ pure $CaCO_3$ will be required to neutralise $50 \ mL$ of $0.5 \ M \ HCl$ solution according to the following reaction? (In $g$)
$CaCO_{3(s)} + 2HCl_{(aq)} \rightarrow CaCl_{2(aq)} + CO_{2(g)} + H_2O_{(l)}$
[Calculate up to the second decimal place]

How many moles of potassium chlorate $(KClO_3)$ are required to be heated to produce $11.2 \text{ L}$ of oxygen gas at $STP$?

$A$ $20 \ mL$ solution of $KMnO_4$ with a concentration of $1 \ N$ reacts with $20 \ mL$ of oxalic acid. The weight of oxalic acid in the $1 \ N$ solution is ......... $g$.