What is the mass of$-$
$\left(a\right)$ $1$ mole of nitrogen atoms?
$\left(b\right)$ $4$ moles of aluminium atoms(Atomic mass of aluminium $=27)?$
$\left(c\right)$ $10$ moles of sodium sulphite $\left(N{a}_{2}S{O}_3\right)?$

(a) 1 mole of nitrogen atoms=$1\times massofN=1\times 14=14g$

(b) 4 moles of aluminium atoms=$4\times 27=108g$

(c) 10 moles of sodium sulphite($N{a}_{2}S{O}_3$)=$10\times MassofN{a}_{2}S{O}_3$.

Mass of $N{a}_{2}S{O}_3=2\times MassofNaatom+1\times MassofSatom+3\times MassofOatom$

$=2\times 23+1\times 32+3\times 16=46+32+48=126g/mol$

$\therefore 10molesofN{a}_{2}S{O}_3=10\times 126=1260g$