The number of chlorine atoms in $1.98 \ g$ of $BaCl_2$ is ..... (Atomic weight of $Ba = 137$,$Cl = 35.5$)

If $8 \ g$ of $NaOH$ is dissolved in $1 \ L$ of solution,its molarity will be ....... $M$.

$28 \ g$ $KOH$ is required to completely neutralize $CO_2$ produced on heating $60 \ g$ of impure $CaCO_3$. The percentage purity of $CaCO_3$ is approximately (molar masses of $KOH$ and $CaCO_3$ are $56$ and $100 \ g \ mol^{-1}$, respectively).

$A$ $10 \ g$ effervescent tablet containing sodium bicarbonate $(NaHCO_3)$ and oxalic acid $(H_2C_2O_4)$ releases $0.25 \ L$ of $CO_2$ at $T = 298.15 \ K$ and $p = 1 \ bar$. If the molar volume of $CO_2$ is $25.0 \ L \ mol^{-1}$ under these conditions,what is the percentage by mass of sodium bicarbonate in each tablet? [Molar mass of $NaHCO_3 = 84 \ g \ mol^{-1}$,Molar mass of $H_2C_2O_4 = 90 \ g \ mol^{-1}$]

$A$ $100 \ mL$ solution of $CH_3CH_2MgBr$ on treatment with methanol produces $2.24 \ mL$ of a gas at $STP$. The weight of gas produced is $......mg$. [nearest integer]

The right option for the mass of $CO_2$ produced by heating $20 \ g$ of $20 \%$ pure limestone is $........ \ g$ (Atomic mass of $Ca = 40$) $[CaCO_3 \stackrel{1200 \ K}{\longrightarrow} CaO + CO_2]$