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Question: How much energy (approx) is required to melt 450 g of ice at \[{\text{ }}0^\circ {\text{C }}\]? A....

How much energy (approx) is required to melt 450 g of ice at  0∘C {\text{ }}0^\circ {\text{C }}?
A.1500 KJ
B.1600 KJ
C.150 KJ
D.None of these

Explanation

Solution

To calculate the energy required to melt ice we must know the specific latent heat of fusion to change the phase. Using the latent heat and mass of ice we will calculate the energy required.
Formula used:
 Q=LIce×m {\text{ Q}} = {{\text{L}}_{{\text{Ice}}}} \times {\text{m }}
Here  Q {\text{ Q }}is latent heat,  LIce {\text{ }}{{\text{L}}_{{\text{Ice}}}}{\text{ }}is the specific latent heat and m is the mass of body. Specific latent heat for ice is  0.334 KJ/g {\text{ 0}}{\text{.334 KJ}}/{\text{g }}

Complete step by step answer:
Latent heat is the energy released or absorbed when a substance undergoes a phase change during a constant temperature. Whenever a phase change occurs for example a solid change into liquid or a liquid change into gas or gas change into solid then the temperature during that process remains constant contrary to what we expected the temperature should increase. To change phase we have to give the energy and we know when we provide energy then the temperature of the system should increase. When phase change occurs all the temperature that is provided to the system is consumed in breaking the bonds, for the conversion of solid to liquid. During that not even a single degree rise in temperature occurs until all the solid gets converted into liquid.
As soon as the solid gets converted into liquid the rise in temperature occurs when we provide energy. Specific latent heat is referred to the amount of energy that is required to bring the phase change in 1 gram of the substance.
Specific latent heat is given to us, so putting the known variables in the formula we will get:
 Q= 0.334 KJ/g ×450 g =150.3 KJ {\text{ Q}} = {\text{ 0}}{\text{.334 KJ}}/{\text{g }} \times 450{\text{ g }} = 150.3{\text{ KJ }}

Hence, the correct option is C.

Note:
The process of conversion of ice to liquid is known as melting. During this phase change the energy is absorbed by the system and hence melting is an endothermic process and the entropy of the system increases due to increase in degree of movement.