Question

The specific latent heat of fusion of ice is:
\[\begin{align}
  & A.~~~~~~~~4.2J{{g}^{-1}}{}^{0}{{C}^{-1}} \\
 & B.~~~~~~~~4200Jk{{g}^{-1}}{}^{0}{{C}^{-1}} \\
 & C.~~~~~~~~336J{{g}^{-1}} \\
 & D.~~~~~~~~336,000J{{g}^{-1}} \\
\end{align}\]

Answer 1

Hint: Latent heat of fusion of ice is the amount of heat required to convert unit gram ice to water. Latent heat of fusion of a substance is calculated or determined experimentally. Its unit is $Jk{{g}^{-1}}$, so this rules out some of the given options too.

Complete Step By Step Solution:
Latent heat of fusion of a substance in $J{{g}^{-1}}$ is the amount of energy required (in joule) to convert one gram of the substance from solid state to liquid state. It is represented by L.
So, latent heat of fusion of ice is the amount of heat required to convert unit gram ice to water. The energy required to convert m gram of a substance having latent heat of fusion L, is given by mL.
When a substance reaches its melting point and is still subjected to heat, this heat does not further raise the temperature of the substance; instead it is used to weaken the interaction forces between molecules of solid, so that the substance can be converted to liquid state.
The SI unit of latent heat of fusion is given by
$Jk{{g}^{-1}}$
The value of specific latent heat of fusion of ice is calculated to be \[~336J{{g}^{-1}}\]
So, the correct option is C.

Note: If you heat any solid substance, its temperature will rise but after a specific temperature the temperature of the substance stops rising (this temperature is called melting point of the substance). This is because this heat energy is being utilized as the latest heat of fusion. The same thing happens when we heat a liquid substance. Here, the heat is being utilized as the latest heat of vaporization. Also, we have reached what is called boiling point of the liquid.