How many kilograms of $CaCO_3$ must be heated to obtain $56$ kilograms of $CaO$? [Atomic masses: $Ca = 40, C = 12, O = 16$]

Haemoglobin contains $0.33\%$ of iron by weight. The molecular weight of haemoglobin is approximately $67200$. The number of iron atoms (At. wt. of $Fe = 56$) present in one molecule of haemoglobin is

The amount of iron $(Fe)$ in $g$ which can be produced from $600 \ g$ of magnetite ore is [Atomic mass of $Fe$ : $55.8$]

$16.8 \ L$ of a gas mixture containing $H_2$ and $O_2$ is formed at $NTP$ by the electrolysis of water. What is the mass of the electrolysed water in $g$?

$1 \ mol$ of metal '$M$' reacts completely with alcohol to give $1.5 \ mol$ of $H_2$. What is the valency of metal '$M$'?

$20 \, mL$ of a $1 \, N$ solution of $KMnO_4$ just reacts with $20 \, mL$ of a solution of oxalic acid. The weight of oxalic acid crystals in $1 \, L$ of the solution is $... \, g$