If $30 \ mL$ of $H_2$ and $20 \ mL$ of $O_2$ react to form water,what is left at the end of the reaction?

When $22.4 \ L$ of $H_{2(g)}$ is mixed with $5.6 \ L$ of $Cl_{2(g)}$,each at $S.T.P.$,the moles of $HCl_{(g)}$ formed after completion of the reaction is closest to $.... \ mol$.

$CaCO_3 + 2HCl \to CaCl_2 + CO_2 + H_2O$. In this chemical reaction,what will be the amount of $CaCl_2$ produced when $10 \ g$ of calcium carbonate and $200 \ mL$ of $0.75 \ M$ $HCl$ are used? $.............. \ g$

$A$ reaction gas mixture contains $50 \%$,$30 \%$,and $20 \%$ of $A$,$B$,and $C$ by volume,respectively. The mixture undergoes the following reactions:
$1. A + 2B \rightarrow P_1$
$2. 4P_1 + 3C \rightarrow P_2$
$P_1$ and $P_2$ are two products of the reactions. Choose the correct answer if the reaction completes.

For the reaction $2Al + 3MnO \xrightarrow{\Delta} Al_2O_3 + 3Mn$; If $108 \ g$ of $Al$ and $213 \ g$ of $MnO$ are heated,then which of the following is incorrect?

An electric discharge is passed through a mixture containing $50 \ mL$ of $O_{2(g)}$ and $50 \ mL$ of $H_{2(g)}$. The volume of the product $(H_2O)$ formed at $110 \ ^oC$ will be ............... $mL$.