The symbol of S.I unit of amount of substance is:

$180 \mathrm{g}$ of water can be represented as

(i) $5 \mathrm{g}$ mole of water
(ii) $10$ moles of water
(iii) $6.023\times {10}^{23}$ molecules of water
(iv) $6.023\times {10}^{24}$ molecules of water.

Define the following term

Avogadro's number