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JAMB Physics 2017 Paper

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Question : 8

Total: 49

Calculate the specific latent heat of vaporization of steam of 1.13 x 106J of heat energy is required to convert 15kg of steam to water.

7.53 x 105 Jkg $^{-1}$
7.53 x 10-2Jkg $^{-1}$
$7.53 \times 10^{4}$ Jkg $^{-1}$
7.53 x 10-3Jkg $^{-1}$

Solution:

Concept:

Specific latent heat is the amount of heat energy needed to change the state of

1\,\text{kg}

of a substance without changing its temperature.

Explanation:

The heat energy is given by

Q = mL

, where

m

is the mass and

L

is the specific latent heat.

Rearrange to find

L

:

L = \frac{Q}{m}

.

Substitute

Q = 1.13 \times 10^{6}\,\text{J}

and

m = 15\,\text{kg}

.

L = \frac{1.13 \times 10^{6}}{15}

.

L = 7.53 \times 10^{4}\,\text{Jkg}^{-1}

.

Answer:

L = 7.53 \times 10^{4}\,\text{Jkg}^{-1}

, which matches option C.

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