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  4. A block of ice of mass mg is at -5° C at atmospheric pressure. It is given 420J of heat so that the ice starts melting. Finally, when the ice-water mixture is in equilibrium, it is found that 1g of ice has melted. Assuming there is no other heat exchange in the process, the value of m is [heat capacity of ice = 2100JKg- 1° C- 1 and latent heat of ice = 3.36 × 105 Jkg- 1 ]

Q. A block of ice of mass $mg$ is at $-5^\circ C$ at atmospheric pressure. It is given $420J$ of heat so that the ice starts melting. Finally, when the ice-water mixture is in equilibrium, it is found that $1g$ of ice has melted. Assuming there is no other heat exchange in the process, the value of $m$ is
[heat capacity of ice = $2100JKg^{- 1}^\circ C^{- 1}$ and latent heat of ice = $3.36 \times 10^{5}$ $Jkg^{- 1}$ ]

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Solution:

The heat capacity given in the question is really the specific heat. Now applying the heat exchange equation:
$420=\left(m \times \left(10\right)^{- 3}\right)\left(2100\right)\left(5\right)+\left(1 \times \left(10\right)^{- 3}\right)\left(\right.3.36\times \left(10\right)^{5}\left.\right)$
Solving this equation, we get
$m$ $=8g$
$\therefore $ The correct answer is 8.

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