One mole of magnesium nitride on the reaction with an excess of water gives

How many grams of $3-$hydroxypropanal $(MW=74)$ must be dehydrated to produce $7.8 \ g$ of acrolein $(MW=56)$ $(C_3H_4O)$ if the percentage yield is $64\%$? (Round off to the nearest integer).
[Given: Atomic masses: $C = 12.0 \ u, H = 1.0 \ u, O = 16.0 \ u$]

Concentrated nitric acid is labelled as $75 \%$ by mass. The volume in $mL$ of the solution which contains $30 \ g$ of nitric acid is $.............$ Given : Density of nitric acid solution is $1.25 \ g / mL$

$A$ sample of $NaNO_3$ weighing $0.38 \ g$ is placed in a $50.0 \ mL$ volumetric flask. The flask is filled to the mark with water. What is the molarity of the solution?

The volume of oxygen at $STP$ required to burn $2.4 \,g$ of carbon completely is $.... \,L$

Calculate the mass of sodium acetate $(CH_{3}COONa)$ required to make $500 \,mL$ of $0.375 \,M$ aqueous solution. Molar mass of sodium acetate is $82.0245 \,g \,mol^{-1}$.