The density of a gas at $STP$ is $2.86 \, g \, L^{-1}$. Which of the following is the gas?

When $100 \, g$ of $CaCO_3$ reacts with $1 \, N \, HCl$,how many grams of $CO_2$ will be obtained upon completion of the reaction?

Which of the following contains the maximum number of carbon atoms?

How many kilograms of $CaCO_3$ must be heated to obtain $56$ kilograms of $CaO$? [Atomic masses: $Ca = 40, C = 12, O = 16$]

$30.0 \ mL$ of the given $HCl$ solution requires $20.0 \ mL$ of $0.1 \ M$ sodium carbonate solution for complete neutralisation. What is the volume of this $HCl$ solution required to neutralise $30.0 \ mL$ of $0.2 \ M$ $NaOH$ solution (in $mL$)?

What will be the amount of $MgCl_2$ produced when $17 \ g$ of $HCl$ is reacted with an excess of $MgO$ in the following reaction?
$MgO + 2HCl \longrightarrow MgCl_2 + H_2O$