Calculate the amount of energy in kilojoules needed to change 225 g of water ice at -10 C to steam at 125 C. The following constants may be useful:
Cm(ice)=36.57 J/(mol*C)
Cm(water)=75.40 J/(mol*C)
Cm(steam)=36.04 J/(mol*C)
Delta H(fus)=+6.01 kJ/mol
Delta H(vap)=+40.67 kJ/mol
3 answers
I will be happy to check your work. Do these in order (heat ice to OC), melt ice, heat water to 100C, vaporize, heat steam.
These are the numbers I calculated:
Cm(ice)=4.57 kJ
Delta H(fus)=75.06 kJ
Cm(water)=94.17 kJ
Delta H(vap)=507.97 kJ
Cm(steam)=11.25 kJ
Total= 693 kJ
Cm(ice)=4.57 kJ
Delta H(fus)=75.06 kJ
Cm(water)=94.17 kJ
Delta H(vap)=507.97 kJ
Cm(steam)=11.25 kJ
Total= 693 kJ
The only one I disagree with slightly is vaporization. I obtained 507.95 kJ. I don't round anything until the last calculation; i.e., (225/18.015) x 40.67 = 507.95171 which rounds to 507.95 kJ.
2 answers