Question
Which of the following correctly represents $$180\,g$$ of water ?
(i) $$5{\text{ }}moles$$ of water
(ii) $$10{\text{ }}moles$$ of water
(iii) $${\text{6}}{\text{.023}} \times {\text{1}}{{\text{0}}^{23}}$$ molecules of water
(iv) $${\text{6}}{\text{.023}} \times {\text{1}}{{\text{0}}^{24}}$$ molecules of water
A.
(i) and (ii)
B.
(i) and (iv)
C.
(ii) and (iv)
D.
(ii) and (iii)
Answer :
(ii) and (iv)
Solution :
$$\eqalign{
& 18\,g\,\,{\text{of}}\,\,{H_2}O = 1\,mol \cr
& 180\,g\,\,{\text{of}}\,\,{H_2}O = 10\,mol \cr} $$
$$18\,g\,\,{\text{of}}\,\,{H_2}O$$ $$ = 6.023 \times {10^{23}}\,\,{\text{molecules}}\,\,{\text{of}}\,\,{H_2}O$$
$$\eqalign{
& 180\,g\,\,{\text{of}}\,\,{H_2}O = \frac{{6.023 \times {{10}^{23}}}}{{18}} \times 180 \cr
& = 6.023 \times {10^{24}}\,\,{\text{molecules}}\,\,{\text{of}}\,\,{H_2}O \cr} $$