Question

The enthalpy of fusion of ice is 6 kjmol-1 the heat capacity of water is  what is the smallest number of ice cubes at 0°c, each containing one mole of water that are needed to cool 500 g of liquid water from 20° to 0° c?

Answer 1

Molecular mass of hydrogen = 1  

Molecular mass of oxygen =16  

Molecular mass of water = 18 gram per mole  

As,

n = m / M

n = 500 / 18

n = 27.8 moles  

For cooling 27.8 moles at 20 = 27.8 x 75.4 x 20 = 41.922 kilo joule

41.922/6  = 6.987 that is approximately equal to 7  

So, the number of ice cubes that are required to cool the water will be 7.