Question

How many joules of energy must be removed from 192 g of water at 23.6 C to form ice at 0 C? Significant digits is set to 3

Answer 1

Remember it takes energy to go from a liquid to a solid. That's why we get those flat areas in cooling curves.

So you need to calculate two energies

1)The energy to cool the liquid water down to 0 degrees
192 g of H2O(l) at 23.6 degrees to 192g of H2O(l) at 0 degrees
and then
2)The energy to freeze the liquid water into ice
192 g of H2O(l) to 192 g of H2O(s)

we have the equation: energy = m x C x T

= 192 x 4.1855 J/g K x 23.6                                                        ( heat capacity= 4.1855 )

= 18965.3376 J

WE HAVE energy= heat of fusion x mass

= 334 x 192 g             ( LATENT HEAT OF FUSION OF WATER= 334)

= 64128 J

adding both ( 18965.3376 J + 64128 J ) gives approx 5.4 x 10^-4 J