States of Matter - Result Question 2-2

2. At $100^{\circ} \mathrm{C}$ and 1 atm if the density of the liquid water is $1.0 \mathrm{~g} \mathrm{~cm}^{-3}$ and that of water vapour is $0.0006 \mathrm{~g} \mathrm{~cm}^{-3}$, then the volume occupied by water molecules in 1 L of steam at this temperature is

(2000, 1M)

(a) $6 \mathrm{~cm}^3$

(b) $60 \mathrm{~cm}^3$

(c) $0.6 \mathrm{~cm}^3$

(d) $0.06 \mathrm{~cm}^3$

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Answer:

Correct Answer: 2. (c)

Solution:

Let us consider, 1.0 L of liquid water is converted into steam.

Volume of $\mathrm{H}_2 \mathrm{O}(l)=1 \mathrm{~L}$, mass $=1000 \mathrm{~g}$

$\Rightarrow \quad$ Volume of 1000 g steam $=\dfrac{1000}{0.0006} \mathrm{~cm}^3$

$\because$ Volume of molecules in $\dfrac{1000}{0.0006} \mathrm{~cm}^3$ steam $=1000 \mathrm{~cm}^3$

$\therefore$ Volume of molecules in

$ 1000 \mathrm{~cm}^3 \text { steam }=\dfrac{1000}{1000} \times 0.0006 \times 1000=0.60 \mathrm{~cm}^3 $