Question

The fluorocarbon compound C2Cl3F3 has a normal boiling point of 47.6 ∘C. The specific heats of C2Cl3F3(l) and C2Cl3F3(g) are 0.91 J/g⋅K and 0.67 J/g⋅K, respectively. The heat of vaporization for the compound is 27.49 kJ/mol. Calculate the heat required to convert 74.0 g of C2Cl3F3 from a liquid at 10.55 ∘C to a gas at 87.40 ∘C.

Answer 1

1. Sensible heat needs to be transferred to the liquid from 10.55 to 47.6 deg.c   , sensible heat= mass * specific heat of liquid* temperature difference = 74*0.91*(47.6-10.55) =2495 Joules=2.495 KJ

at 47.6 deg,c, latent heat need to be supplied to C2Cl3F3 to convert into vapor. Since latent heat is given in KJ/mol, mass of 74 of C2Cl3F3 need to be converted to moles

moles of C2Cl3F3 in 74 gm = mass/molar mass

molar mass of C2Cl3F3= 2*12+3*35.5+3*19= 187.5 gm/mole

moles of C2Cl3F3= 74/187.5= 0.395

2. heat to be supplied to convert 74 gm of 0.395 moles of C2Cl3F3 into vapor = moles* latent heat ( Kj/mole)= 0.395*27.49 Kj=10.85 Kj

3. From 47.6 to 87.4 deg,c it is the sensible heat of vapor= 74*0.67*(87.4-47.6) = 1973 Joules = 1.973 KJ

total heat to be supplied = sum of 1, 2 and 3 = 2.495+10.85+1.973=15.318 KJ