Question

Calculate the amount of heat necessary to change 200.0 g of ice at -15.0◦C to steam at 110◦C. Is this process endothermic or exothermic?

Answer 1

Heat required to change the temperature of ice from - 15C to 0C

Q1 = m x Cp x (T2-T1)

= 200g x 2.108 J/gC x (0 + 15) C

= 6324 J

Phase change at 0 C from ice to liquid water

Q2 = m x latent heat of fusion

= 200 g x 6.02 kJ/mol x 1 mol/18g x 1000 J/kJ

= 66888.88 J

Heat required to change the temperature of liquid from 0C to 100C

Q3 = m x Cp x (T2-T1)

= 200g x 4.184 J/gC x (100-0) C

= 83680 J

Phase change at 100 C from liquid water to steam

Q4 = m x latent heat of vaporization

= 200 g x 40.6 kJ/mol x 1 mol/18g x 1000 J/kJ

= 451111.11 J

Heat required to change the temperature of syean from 100 C to 110C

Q5 = m x Cp x (T2-T1)

= 200g x 1.996 J/gC x (110-100) C

= 3992 J

Total amount of heat required

= 6324 + 66888.88 + 83680 + 451111.11 + 3992

= 611995.99 J

= 611.99599 kJ = 612 kJ

The process is endothermic