The chemical symbol for nitrogen gas is

What is meant by the following?
$(i)$ Molar mass
$(ii)$ Valency

Mention the name given to the number of $6.022 \times 10^{23}$ particles.

Which of the following correctly represents $360 \, g$ of water?
$(i)$ $2$ moles of $H_2O$
$(ii)$ $20$ moles of water
$(iii)$ $6.022 \times 10^{23}$ molecules of water
$(iv)$ $1.2044 \times 10^{25}$ molecules of water

Write the names of the following compounds:
$(a)$ $NiS$
$(b)$ $Mg(NO_3)_2$
$(c)$ $Na_2SO_4$
$(d)$ $Al(NO_3)_3$
$(e)$ $K_3PO_4$
$(f)$ $Ca_3N_2$

Calculate the number of moles of magnesium present in a magnesium ribbon weighing $12 \, g$. The molar atomic mass of magnesium is $24 \, g \, mol^{-1}$. (in $, mol$)