$60 \ mL$ $NaOH$ solution is required for complete neutralization of $0.98 \ g$ orthophosphoric acid. The concentration of $NaOH$ solution is ............. $M$.

When $22.4 \, L$ of $C_4H_8$ at $STP$ is burnt completely,$89.6 \, L$ of $CO_2$ gas at $STP$ and $72 \, g$ of water are produced. The volume of the oxygen gas at $STP$ consumed in the reaction is closest to $.... \, L$

$7.8 \ g$ of a compound having molecular formula $C_6H_6$,on reacting with $CH_3COCl / AlCl_3$ gives $8.4 \ g$ of a product which has molecular formula $C_8H_8O$. Calculate the percentage yield of the product $C_8H_8O$. (Given atomic weights of $H$,$C$ and $O$ respectively are $1$,$12$ and $16$) (in $\%$)

Reaction of $x \ g$ of $Sn$ with $HCl$ quantitatively produced a salt. The entire amount of the salt reacted with $y \ g$ of nitrobenzene in the presence of the required amount of $HCl$ to produce $1.29 \ g$ of an organic salt (anilinium chloride) quantitatively.
$(1)$ The value of $x$ is. . . . .
$(2)$ The value of $y$ is. . . . .

The normality of $1 \ M$ solution of $H_3PO_4$ will be.....$N$

One mole of calcium phosphide on reaction with excess of water gives