What is a limiting reagent?

If $0.50 \ mol$ of $CaCl_2$ is mixed with $0.20 \ mol$ of $Na_3PO_4$,the maximum number of moles of $Ca_3(PO_4)_2$ which can be formed,is

When copper is reacted with a certain concentration of nitric acid,nitric oxide and nitrogen dioxide are produced in equal volumes according to the following reaction:
$xCu + yHNO_3 \to xCu(NO_3)_2 + NO + NO_2 + 3H_2O$
What are the stoichiometric coefficients $x$ and $y$?

Percentage loss in mass on heating a mixture of $Na_2CO_3$ and $CaCO_3$ containing equal mass of the two components will be ............. $\%$

What will be the volume of the mixture after the reaction? $litre$
$NH_3(4 \ litre) + HCl(1.5 \ litre) \to NH_4Cl(s)$

What is the value of $PV$ type of work for the following reaction at $1 \ bar$ pressure (in $J$)? The reaction is: $C_2H_4(g) + HCl(g) \rightarrow C_2H_5Cl(g)$. Given volumes are $200 \ mL$ of $C_2H_4$ and $150 \ mL$ of $HCl$.