The decomposition of $CaCO_3$ produces $11.2 \, dm^3$ of $CO_2$ gas at $STP$. What mass of $KOH$ in grams is required to completely neutralize this gas?

Ferrous sulphate heptahydrate is used to fortify foods with iron. The amount (in $grams$) of the salt required to achieve $10 \; ppm$ of iron in $100 \; kg$ of wheat is
Atomic weight : $Fe = 55.85$,$S = 32.0$,$O = 16.00$

How many grams of $BaCO_3$ are produced when excess $CO_2$ is passed through $0.205 \ mol$ of $Ba(OH)_2$?

The heat of combustion of methane is given by the following equation. How many grams of methane are required to produce $445 \ kJ$ of heat (in $g$)?
$CH_4 + 2O_2 \rightarrow CO_2 + 2H_2O \ (\Delta H = -891 \ kJ/mol)$

Find the molecular weight of a solid containing $20\%$ by mole of $S$ atoms,whose $400\ g$ provides just sufficient $S$ atoms to produce enough $H_2SO_4$ to neutralise $100\ g$ $NaOH$.

$25 \ mL$ of a solution of $Na_2CO_3$ having a specific gravity of $1.25$ required $32.9 \ mL$ of a solution of $HCl$ containing $109.5 \ g$ of the acid per litre for complete neutralization. Calculate the volume of $0.84 \ N$ $H_2SO_4$ that will be completely neutralized by $125 \ g$ of the $Na_2CO_3$ solution (in $mL$).