Which of the following is formed when calcium combines with oxygen?

In the preparation of baking soda,what is the ratio of $H_2O$ and $CO_2$ used to react with $Na_2CO_3$ to form $NaHCO_3$?

$A + 2B + 3C \rightleftharpoons AB_2C_3$. Reaction of $6.0 \ g$ of $A$,$6.0 \times 10^{23}$ atoms of $B$,and $0.036 \ mol$ of $C$ yields $4.8 \ g$ of compound $AB_2C_3$. If the atomic mass of $A$ and $C$ are $60$ and $80 \ amu$,respectively,the atomic mass of $B$ is .............. $amu$ (Avogadro no. $= 6 \times 10^{23}$)

The mass of $Mg_3N_2$ produced if $48 \ g$ of $Mg$ metal is reacted with $34 \ g$ $NH_3$ gas is:
$3Mg + 2NH_3 \to Mg_3N_2 + 3H_2$

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 quantity of carbon dioxide is produced when $2 \,mol$ of carbon is burnt in $16 \,g$ of dioxygen (in $\,g$)?