What is the mass of potassium chloride produced when $12.25 \ g$ of potassium chlorate undergoes decomposition (in $g$)? (Atomic masses: $K=39, Cl=35.5, O=16$)

$X \ g$ of $Ca$ [atomic mass $= 40$] dissolves completely in concentrated $HCl$ solution to produce $5.04 \ L$ of $H_2$ gas at $STP$. The value of $X$ is closest to

$100 \ mL$ of $PH_3$ on decomposition produces phosphorus and hydrogen. The change in volume is ............... $mL$ increase.

The volume of $0.6 \, M$ $NaOH$ required to neutralize $30 \, cm^3$ of $0.4 \, M$ $HCl$ is ........ $cm^3$.

At $STP$,for complete combustion of $3\, g$ of $C_2H_6$,the required volume of $O_2$ will be - ............. $litre$.

In the reaction $SO_{2(g)} + 1/2 O_{2(g)} \to SO_{3(g)}$,how many liters of air at $STP$ are required for the complete conversion of $6.4 \, g$ of $SO_2$ to $SO_3$ (in $, L$)? (Assume air contains $20 \% \, O_2$ by volume).