Question

From the data below, calculate the total heat (in J) needed to convert 0.896 mol of gaseous ethanol at 300.0°C and 1 atm to liquid ethanol at 25.0°C and 1 atm:

b.p. at 1 atm:78.5°C

ΔH⁰_vap

:40.5 kJ/mol

c_gas:1.43 J/g·°C

c_liquid:2.45 J/g·°C

Answer 1

Molar mass of C2H5OH = 2*MM(C) + 6*MM(H) + 1*MM(O)

= 2*12.01 + 6*1.008 + 1*16.0

= 46.068 g/mol

we have below equation to be used:

mass of C2H5OH,

m = number of mol * molar mass

= 0.896 mol * 46.068 g/mol

= 41.28 g

Ti = 300.0 oC

Tf = 25.0 oC

Cg = 1.43 J/g.oC

Heat released to convert vapour from 300.0 oC to 78.5 oC

Q1 = m*Cg*(Ti-Tf)

= 41.28 g * 1.43 J/g.oC *(300-78.5) oC

= 13075.2336 J

Hovap = 40.5J/mol

Heat released to convert gas to liquid at 78.5 oC

Q2 = n*HVap

= 0.896 mol *40.5 J/mol

= 36.2907 J

Cl = 2.45 J/g.oC

Heat released to convert liquid from 78.5 oC to 25.0 oC

Q3 = m*Cl*(Ti-Tf)

= 41.28 g * 2.45 J/g.oC *(78.5-25) oC

= 5410.776 J

Total heat released = Q1 + Q2 + Q3

= 13075.2336 J + 36.2907 J + 5410.776 J

= 18522 J

Since it is heat released, please enter your answer with negative sign

Answer: 1.85*10^4 J