How much $H_2$ gas (in $L$) will be produced at $STP$ when $27 \ g$ of aluminum reacts with aqueous $NaOH$?

How many grams of iron are theoretically produced by the reduction of $1 \ kg$ of $Fe_2O_3$?

Three solutions of $HCl$ having normalities $12 \ N$,$6 \ N$,and $2 \ N$ are mixed to obtain a solution of $4 \ N$ normality. Which among the following volume ratios is incorrect for the above mixture?

$A$ metal chloride contains $55.0 \%$ of chlorine by weight. $100 \ mL$ of vapours of the metal chloride at $STP$ weigh $0.57 \ g$. The molecular formula of the metal chloride is $...$. (Given: Atomic mass of chlorine is $35.5 \ u$)

$0.092 \ g$ of a compound with the molecular formula $C_3H_8O_3$ on reaction with an excess of $CH_3MgI$ gives $67.00 \ mL$ of methane at $STP$. The number of active hydrogen atoms present in a molecule of the compound is

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]