The mass of one steel screw is $4.11 \, g$. Find the mass of one mole of these steel screws. Compare this value with the mass of the Earth $(5.98 \times 10^{24} \, kg)$. Which one of the two is heavier and by how many times?

What is the fraction of the mass of water due to neutrons?

The difference in the mass of $100 \, mol$ each of sodium atoms and sodium ions is $5.48002 \, g$. Compute the mass of an electron.

$(a)$ Calculate the number of moles in $112 \, g$ of iron.
$(b)$ Calculate the mass of $0.5$ mole of sugar $(C_{12}H_{22}O_{11})$.
$(c)$ Calculate the number of atoms in $8 \, g$ of oxygen $(O_2)$ molecules.
(Atomic mass of $Fe = 56 \, u, C = 12 \, u, H = 1 \, u, O = 16 \, u, N_A = 6.022 \times 10^{23} \, mol^{-1}$)

$A$ sample of vitamin $C$ is known to contain $2.58 \times 10^{24}$ oxygen atoms. How many moles of oxygen atoms are present in the sample?

Find the ratio by mass of the combining elements in the following compounds. (You may use Appendix $-III$)
$(a)$ $CaCO_{3}$ $(b)$ $MgCl_{2}$
$(c)$ $H_{2}SO_{4}$ $(d)$ $C_{2}H_{5}OH$
$(e)$ $NH_{3}$ $(f)$ $Ca(OH)_{2}$