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

The molecular formula of a commercial resin used for exchanging ions in water softening is $C_8H_7SO_3^- Na^+$ $(Mol. \ wt. 206)$. What would be the maximum uptake of $Ca^{2+}$ ions by the resin when expressed in mole per gram resin?

What is the mass of oxygen in $g$ required to produce enough $CO$ for the complete reduction of $1.6 \ kg$ of $Fe_2O_3$ (molar mass $= 160 \ g/mol$)?

Number of moles of oxygen gas evolved by electrolysis of $180 \ g$ of water?

To change the strength of $25 \, mL$ of $0.15 \, M$ $HCl$ to $0.1 \, M$,the quantity of water that is to be added is.......$mL$

The ratio of mass percentage (w/w) of $C : H$ in a hydrocarbon is $12 : 1$. It has two carbon atoms. The weight (in $g$) of $CO_2(g)$ formed when $3.38 \ g$ of this hydrocarbon is completely burnt in oxygen is : (Given : Molar mass in $g \ mol^{-1}$, $C : 12, H : 1, O : 16$)