A calorimeter of water equivalent 15 g contains 165 g of water at 25- C- Steam at 100- C is passed through the water for some time- The temperature is increased to 30- C and the mass of the calorimeter and its contents is increased by 1-5 g- Calculate the latent heat of vaporization of water- Heat capacity of water is 1 cal - g - CA- 630 cal - gB- 1530 cal - gC- 530 cal - gD- 1500 cal - g

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Standard XII

Physics

Calorimetry

A calorimeter...

Question

A calorimeter of water equivalent 15g contains 165g of water at $25^{\circ} C$ . Steam at $100^{\circ} C$ is passed through the water for some time. The temperature is increased to $30^{\circ} C$ and the mass of the calorimeter and its contents is increased by 1.5 g. Calculate the latent heat of vaporization of water. Heat capacity of water is $1 c a l / g^{\circ} C$

630 cal/g

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530 cal/g

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1530 cal/g

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1500 cal/g

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Solution

The correct option is B 530 cal/g
Let L be the specific latent heat of vaporization of water. The mass of the steam condensed is 1.5g. Heat lost in condensation of steam is
$Q_{1} = (1.5 g) L$
The condensed water cools from $100^{\circ} C$ to $300^{\circ} C$ . Heat lost in this process is -
$Q_{2} = (1.5 g) (1 c a l / g^{\circ} C) (70^{\circ} C) = 105 c a l$
Heat supplied to the calorimeter and to the cold water during the rise in temperature from $25^{\circ} C$ to $30^{\circ} C$ is -
$Q_{3} = (15 g + 165 g) (1 c a l / g^{\circ} C) (5^{\circ} C) = 900 c a l$
If no heat is lost to the surrounding,
$(1.5 g) L + 105 c a l = 900 c a l$
or $L = 530 c a l / g$

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Similar questions

A calorimeter of water equivalent $15 g$ contains $165 g$ of water at $25^{\circ} C$ . Steam at $100^{\circ} C$ is passed through the water for some time. The temperature is increased to $30^{\circ} C$ and the mass of the calorimeter and its contents is increased by $1.5 g$ . Calculate the specific latent heat of vaporization of water. The heat capacity of water is $1 c a l g^{- 1}^{\circ} C^{- 1}$

Q. A steam at

100^{o} C

is passed into

1 k g

of water contained in a calorimeter of water equivalent

0.2 k g

9^{o} C

, till the temperature of the calorimeter and water in it is increased to

90^{o} C

. The mass of steam condensed in

k g

is nearly:

[sp. heat of water

= 1

c a l / g^{o}

C, latent heat of vaporisation

= 540 c a l / g

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

latent heat of vaporization of water = $540 c a l k g^{-} 1$ , specific heat capacity of water = $10^{3} c a l k g^{-} 1^{\circ} C^{-} 1$

Steam at $100^{\circ} C$ is passed into $1.1 k g$ of water contained in a calorimeter of water equivalent $0.02 k g$ at $15^{\circ} C$ till the temperature of the calorimeter and its contents reaches $80^{\circ} C$ . Considering the latent heat of steam $= 540 c a l g^{- 1}$ $and s$ pecific heat capacity of water $= 4183 J k g^{- 1} K^{- 1}$ ${or}$ $= 1 c a l k g^{- 1} K^{- 1}$ ,
calculate the mass of the steam condensed.

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