$A$ metal oxide contains $75 \%$ metal by mass. If the vapour density of the metal chloride is $89$,what is the atomic weight of the metal?

$50 \ mL$ of $10 \ N \ H_2SO_4$,$25 \ mL$ of $12 \ N \ HCl$,and $40 \ mL$ of $5 \ N \ HNO_3$ were mixed together,and the volume of the mixture was made $1000 \ mL$ by adding water. The normality of the resultant solution will be.....$N$.

Iron sulphide is heated in air to form $A$,an oxide of sulphur. $A$ is dissolved in water to give an acid. The basicity of this acid is

What quantity (in $mL$) of a $45\%$ acid solution of a mono-protic strong acid must be mixed with a $20\%$ solution of the same acid to produce $800 \ mL$ of a $29.875\%$ acid solution?

The volume of $HCl$,containing $73 \ g \ L^{-1}$,required to completely neutralize $NaOH$ obtained by reacting $0.69 \ g$ of metallic sodium with water,is $........ mL$. (Nearest Integer) (Given: molar masses of $Na, Cl, O, H$ are $23, 35.5, 16$ and $1 \ g \ mol^{-1}$ respectively)