Question

Which of the following correctly represents 360 g of water?

(i) $2molesof$ $H_{2}O$
(ii) $20molesofwater$
(iii) $6.022\times {10}^{23}moleculesofwater$
(iv) $1.2044\times {10}^{25}moleculesofwater$

(a) (i)
(b) (i) and (iv)
(c) (ii) and (iii)
(d) (ii) and (iv)

Answer 1

(ii) $20molesof$ $H_{2}O$ = $20\times 18g=360g$ of water, because mass of 1 mole of water is the same as its molar mass i, e., $18g$

(iv) $1.2044\times {10}^{25}$ molecules of water contains
$\frac{1.2044\times {10}^{25}}{N_A}$ number of moles, $N_A=6.023\times {10}^{23}$
$\therefore \frac{1.2044\times {10}^{25}}{6.022\times {10}^{23}}=20moles$

$20molesofwater$ = $20\times 18g$
= $360g$ of water

Hence option D is correct.