$2 \ g$ of aluminium is treated separately with excess of dilute $H_{2}SO_{4}$ and excess of $NaOH$. The ratio of the volumes of hydrogen evolved is

$4.4 \ g$ of an unknown gas occupies $2.24 \ L$ of volume at standard temperature and pressure. The gas may be

$CaCO_3$ reacts with $HCl$ to produce $CaCl_2, CO_2$ and $H_2O$. The approximate mass (in $g$) of $CaCO_3$ required to react completely with $25 \ mL$ of $0.75 \ M \ HCl$ is (atomic mass of $Ca=40, C=12, O=16, Cl=35.5$ and $H=1$).

Number of moles of oxygen gas evolved by electrolysis of $180 \ g$ of water?

What is the percent atom economy if the formula weight of reactants and the formula weight of products are $45 \ u$ and $35 \ u$ respectively (in $\%$)?

$A$ cold drink bottle contains $200 \ mL$ liquid in which $CO_2$ is $0.1 \ M$. Considering $CO_2$ as an ideal gas,the volume of the dissolved $CO_2$ at $S.T.P$ is: (in $L$)