Phosphoric acid $(H_3PO_4)$ is a tribasic acid and one of its salts is sodium dihydrogen phosphate $(NaH_2PO_4)$. What volume of $1 \ M$ $NaOH$ solution should be added to $12 \ g$ of sodium dihydrogen phosphate (mol. wt. $120$) to exactly convert it into trisodium phosphate $(Na_3PO_4)$? (Answer in $mL$)

At sea level,the dry air mass percentage composition is given as nitrogen gas: $70.0$,oxygen gas: $27.0$,and argon gas: $3.0$. If the total pressure is $1.15 \ atm$,calculate the ratio of the following respectively:
$(i)$ partial pressure of nitrogen gas to partial pressure of oxygen gas
$(ii)$ partial pressure of oxygen gas to partial pressure of argon gas
(Given: Molar mass of $N_2$,$O_2$,and $Ar$ are $28, 32$,and $40 \ g \ mol^{-1}$ respectively)

The charge carried by $1 \text{ millimole}$ of $M^{n+}$ ions is $193 \text{ C}$. The value of $n$ is

One litre of a gas at $STP$ weighs $1.16 \ g$. It can possibly be:

The moles of methane required to produce $81 \ g$ of water after complete combustion is $.... \times 10^{-2} \ mol.$ [nearest integer]

$4.0 \, g$ of caustic soda is dissolved in $100 \, mL$ of solution. The normality of the solution is: (in $, N$)