Balance the following chemical equations:
$(i)$ $Cu_2S + O_2 \to Cu_2O + SO_2$
$(ii)$ $Ca_3(PO_4)_2 + H_2SO_4 \to Ca(H_2PO_4)_2 + CaSO_4$

Assign $A, B, C, D$ from the given type of reaction.
$NaBr + AgNO_3 \longrightarrow AgBr \downarrow + NaNO_3$

Moles of conc. $HNO_3$ required to oxidise one mole of sulphur is :
$S + 6HNO_3 \rightarrow H_2SO_4 + 6NO_2 + 2H_2O$

Write about Limiting Reagent.

In the reaction $2H_2 + O_2 \to 2H_2O$,if $6 \ g$ of $H_2$ combines with $64 \ g$ of $O_2$,find the mass of the excess reagent left in $g$.

What is the value of $PV$ type of work for the following reaction at $1 \ bar$ pressure (in $J$)? The reaction is: $C_2H_4(g) + HCl(g) \rightarrow C_2H_5Cl(g)$. Given volumes are $200 \ mL$ of $C_2H_4$ and $150 \ mL$ of $HCl$.