What is obtained when one mole of calcium phosphide is reacted with excess water?

If $1\frac{1}{2}$ moles of oxygen combine with $Al$ to form $Al_2O_3$,the weight of $Al$ used in the reaction is ............. $g$ $(Al=27)$.

$X \ g$ of $Ag$ is dissolved in $HNO_3$ and this solution is treated with excess $NaCl$. If $2.87 \ g$ of $AgCl$ precipitate is obtained,then the value of $X$ is ............. $g$.

Three solutions of $HCl$ having normalities $12 \ N$,$6 \ N$,and $2 \ N$ are mixed to obtain a solution of $4 \ N$ normality. Which among the following volume ratios is incorrect for the above mixture?

How many gram-equivalents of $NaOH$ are required to neutralize $25 \ cm^{3}$ of a decinormal $HCl$ solution?

For the given series of reactions:
$NH_{3(g)} + O_{2(g)} \rightarrow NO_{(g)} + H_2O_{(l)}$
$NO_{(g)} + O_{2(g)} \rightarrow NO_{2(g)}$
To obtain the maximum mass of $NO_2$ from a given mass of a mixture of $NH_3$ and $O_2$,the ratio of the mass of $NH_3$ to $O_2$ should be: