Question

Steam at $100^{\circ} C$ is passed into $1.1 \, kg$ of water contained in a calorimeter of water equivalent $0.02\, kg$ at $15^{\circ} C$ till the temperature of the calorimeter and its contents rises to $80^{\circ} C$. The mass of the steam condensed in $kg$ is

• A. $0.130$
• B. $0.065$
• C. $0.260$
• D. $0.135$

Answer 1

Answer: (A)

Heat is lost by steam in two stages:
(i) for change of state from steam at $100^{\circ} C$ to water at $100^{\circ} C$ is $m \times 540$
(ii) to change water at $100^{\circ} C$ to water at $80^{\circ} C$ is $m \times 1 \times(100$ $80)$,
where $m$ is the mass of steam condensed.
Total heat lost by steam is $m \times 540+m \times 20=560\, m$ (cals) Heat gained by calorimeter and its contents is
$=(1.1+0.02) \times(80-15)=1.12 \times 65 $ cals.
using Principle of calorimetery, Heat gained = heat lost
$\therefore 560 \,m =1.12 \times 65 \,m =0.130\, gm$