Question

How much heat (in kJ) is evolved in converting 1.00 mole of steam at 145.0 °C to ice at -50.0 °C? The heat capacity of ice is 2.09 J/g°C and that of steam is 2.09 J/g°C

Answer 1

We do this in steps   1mol steam mass = molex molar mass = 1 x 18 = 18 g

Heat released cooling steam form 145 C to 100C = specific heat x temp change x mass of steam

                                                      = ( 2.09) x ( 145-100) x 18 = 1692.9 J

Heat releasd in condesation of vapor to liquid water at 100C = mass x enthalphy of condesation in J/g

                                                    = 18 x 2257J/g   = 40626 J

Heat released in cooling water from 100 to 0C = specifi cheat of water x temp change x mass of water

         = 4.184 x 100 x 18 = 7531.2 J

heat released in fusing water to ice at 0C = mass x enthalphy of fusion = 18 x 333.5 = 6003 J

heat released in coolince ice from 0 to -50 C = specifi cheat of cie x temp change x mass of ice

           =   2.09 x 50 x 18 = 1881 J

combining all we get heat lost in converting 1 mol steam to ice at -50C

       = ( 1692.9+40626+7531.2+6003+1881) = 57733 J = 57.7 KJ