Chemistry calculations: Phase changes

[candiishop]

Hi, I'm having trouble answering this question. I don't know how to start. Any help is greatly appreciated Thanks.

 

Using the data below for CCl4, calculate the total energy required to heat 1.24 mol of CCl4 from -43°C to 109°C.

 

Cp(s) = Cp(l) = 132 JK-1mol-1, Cp(g) = 83 JK-1mol-1 Cp: molar heat capacity

melting point = -23°C, boiling point = 77°C

Hm (melting) = 2.50 kJmol-1, Hv (Heat vaporisation)= 33.0 kJmol-1

 

A) 23.0 J

 

B) 67.0 kJ

 

C) 60.3 kJ

 

D) 56.9 kJ

 

E) 22.9 kJ

[candiishop]

Is the answer B?

[Tom Mattson]

Can you show your work? That would make it easier to check!

[candiishop]

phase 1)

q= 1.24 mol x 132J/Kmol x (43-23)K

= 3274J

= 3.27kJ

 

phase 2)

q= 1.24 mol x Delta Hm

= 1.24 mol x 2.5kJ mol-1

= 3.1kJ

 

phase 3)

q= 1.24 mol x 132J/Kmol x (77+23)k

= 16368J

= 16.4 kJ

 

phase 4)

q= 1.24 mol x delta Hv

= 1.24 mol x 33kJmol-1

= 40.92 kJ

 

phase 5)

q= 1.24 mol x 83J/Kmol x (109-77)K

= 3293.44J

= 3.29 kJ

 

:. Total energy (q)= 3.27 + 3.1 + 16.4 + 40.92 + 3.29

= 67.0kJ

 

:. B