Molarity of a given orthophosphoric acid solution is $3 \ M$. Its normality is (in $N$)

What volume of ammonia is required to react with $250 \ mL$ of oxygen by following the reaction at same conditions?
$4NH_3(g) + 5O_2(g) \to 4NO(g) + 6H_2O(g)$

$x$ grams of calcium carbonate was completely burnt in air. The weight of the solid residue formed is $28 \,g$. What is the value of $x$ (in grams)?

$7.5 \ g$ of a gas occupies $5.8 \ L$ of volume at $STP$. The gas is

$18 \ L$ mixture of $N_2$ and $H_2$ gives maximum $6 \ L$ of $NH_3$ at same temperature and pressure. What will be the ratio of $N_2$ and $H_2$ initially taken?

Combustion of glucose $(C_6H_{12}O_6)$ produces $CO_2$ and water. The amount of oxygen (in $g$) required for the complete combustion of $900 \ g$ of glucose is:
[Molar mass of glucose in $g \ mol^{-1} = 180$]