The molecule having an atomicity of $4$ is

$(a)$ $A$ 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?
$(b)$ Write one word for the following:
$(i)$ In a balanced chemical equation,the sum of the masses of reactants and products remains unchanged.
$(ii)$ $A$ group of atoms carrying a fixed charge on them.
$(c)$ Write chemical formulae of the following compounds:
$(i)$ Sodium phosphate
$(ii)$ Ammonium carbonate

The chemical formula of the oxide of an element $X$ is $X_2O_5$. Write the chemical formula of its chloride.

Which of the following correctly represents $360 \,g$ of water?

What is the difference between $2H$ and $H_2$?

One mole of $H_{2}O$ means:
$(i)$ $18 \text{ g}$ of $H_{2}O$
$(ii)$ $6.022 \times 10^{23}$ molecules of $H_{2}O$
$(iii)$ $180 \text{ g}$ of $H_{2}O$
$(iv)$ $1.8 \text{ g}$ of $H_{2}O$