I am completely lost, please explain and show work Part 1: CCl2F2 is considered

Question

I am completely lost, please explain and show work

Part 1: CCl2F2 is considered to be environmentally safe and is used as a refrigerant. The heat of vaporization of CCl2F2 is 289 J/g. What mass of this substance must evaporate in order to freeze (at 0 °C) 2 moles of water initially at 20 °C? The heat of fusion of water is 334 J/g and the specific heat of water is 4.18 J/g-K.

A. 52.0g

B. 26.0g

C. 15.0g

D. 3.01g

E. 2.89g

Part 2: If an empty aluminum can weighs 13.49 g, how much energy does it take to completely melt 12 cans that are initially at 20 °C? (Aluminum melts at 660 °C.) C (s) = 24.2 J/mol-°C DHfus = 10.71 kJ/mol C (!) = 29.3 J/mol-°C DHvap = 294.0 kJ/mol

A. 157.19 kJ

B. 64.26 kJ

C. 92992 kJ

D. 26.20 kJ

E. 15.49 kJ

Explanation / Answer

Qwater = m*C*(Tf-Ti)

2 mol = 36 g of water

Qwater = 36*4.184 * (0-20) = -3012.48 J

Qfreezing = m*LH = 334*36= -12024 J

Total Q = 3012.48 +12024 = -15036.48 J

so..

QCCl2F2 = m*LH of CCl2F2

QCCl2F2 = - Qwater = 15036.48

15036.48 = m*LH

m = 15036.48 /289

m = 52.029 g required

choose A

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