When oxygen is heated in the presence of a catalyst,$15 \%$ of it is converted into ozone. How many grams of oxygen are required to produce $33.6 \, L$ of $O_3$ at $STP$?

What is the weight in $g$ of $90\%$ pure $H_2SO_4$ required to neutralize $5 \ g$ of caustic soda?

$1.25 \ g$ of a solid dibasic acid is completely neutralized by $25 \ mL$ of $0.25 \ M$ $Ba(OH)_2$ solution. The molecular mass of the acid is:

Sodium oxide reacts with water to produce sodium hydroxide. $20.0 \ g$ of sodium oxide is dissolved in $500 \ mL$ of water. Neglecting the change in volume,the concentration of the resulting $NaOH$ solution is $........ \times 10^{-1} \ M.$ (Nearest integer)
[Atomic mass $: Na=23.0, O=16.0, H=1.0]$

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 $mL$)

$5\, g$ of benzene on nitration gave $6.6\, g$ of nitrobenzene. The theoretical yield of the nitrobenzene will be $..............$ $g$.