Amount of oxygen required for combustion of $1 \, kg$ of a mixture of butane and isobutane is ............. $kg$.

$10 \ mL$ of conc. $H_2SO_4$ $(18 \ M)$ is diluted to $1 \ L$. The approximate strength of the dilute acid is $........... \ N$.

For the given series of reactions:
$NH_{3(g)} + O_{2(g)} \rightarrow NO_{(g)} + H_2O_{(l)}$
$NO_{(g)} + O_{2(g)} \rightarrow NO_{2(g)}$
To obtain the maximum mass of $NO_2$ from a given mass of a mixture of $NH_3$ and $O_2$,the ratio of the mass of $NH_3$ to $O_2$ should be:

$A$ $300 \ mL$ bottle of soft drink has $0.2 \ M$ $CO_2$ dissolved in it. Assuming $CO_2$ behaves as an ideal gas,the volume of the dissolved $CO_2$ at $STP$ is $...... \ mL$. (Nearest integer) Given: At $STP$,molar volume of an ideal gas is $22.7 \ L \ mol^{-1}$.

$1.0 \ g$ of pure calcium carbonate was found to require $50 \ mL$ of dilute $HCl$ for complete reaction. The strength of the $HCl$ solution is given by ........ $N$.

$x$ 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)?