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

Calcium carbonate reacts with aqueous $HCl$ to give $CaCl_{2}$ and $CO_{2}$ according to the reaction,
$CaCO_{3(s)} + 2HCl_{(aq)} \rightarrow CaCl_{2(aq)} + CO_{2(g)} + H_{2}O_{(l)}$
What mass of $CaCO_{3}$ is required to react completely with $25 \ mL$ of $0.75 \ M$ $HCl$ (in $g$)?

One mole of methanol when burnt in excess of $O_2$ releases $723 \ kJ \ mol^{-1}$ of heat. If $1 \ mol$ of $O_2$ is used,what will be the amount of heat evolved in $kJ$?

$510 \ mg$ of a liquid on vaporisation in Victor Mayer's apparatus displaces $510 \ cm^3$ of dry air (at $NTP$). The molecular weight of the liquid is:

Chemical equations convey quantitative information on the

When $500 \, mL$ of a gaseous hydrocarbon is burned with sufficient $O_2$,it produces $2.5 \, L$ of $CO_2$ and $3.0 \, L$ of water vapor. What is the molecular formula of the hydrocarbon?