$20.0 \ g$ of a magnesium carbonate sample decomposes on heating to give carbon dioxide and $6.0 \ g$ magnesium oxide. What will be the percentage purity of magnesium carbonate in the sample? (Atomic weight of $Mg = 24$)

What is the value of percent atom economy if the molar mass of reactants is $36 \ u$ and the mass of the desired product is $27 \ u$ (in $\%$)?

When $100 \, ml$ of $0.1 \, M$ $H_2SO_4$ reacts with $Na_2CO_3$, how many liters of $CO_2$ will be produced at $STP$ (in $L$)?

What is the volume (in litres) of oxygen at $STP$ required for complete combustion of $32 \,g$ of $CH_4$? (Molecular weight of $CH_4$ is $16$)

Calculate the amount of $CO_2$ gas produced when $32 \text{ g}$ of $CH_4$ is burned with a sufficient amount of oxygen. (Given: atomic weights of $C=12, O=16, H=1$) (in $\text{ g}$)

Chlorine is prepared in the laboratory by treating manganese dioxide $(MnO_{2})$ with aqueous hydrochloric acid according to the reaction
$4HCl_{(aq)} + MnO_{2(s)} \rightarrow 2H_{2}O_{(l)} + MnCl_{2(aq)} + Cl_{2(g)}$
How many grams of $HCl$ react with $5.0\ g$ of manganese dioxide?