Question

From data below, calculate the total heat (J) needed to convert 0.172 mol of gaseous ethanol (C2H6O) at 451° C and 1 atm to liquid ethanol at 25.0° C and 1 atm.
Boiling point at 1 atm 78.5°C
cgas 1.43 J/g · °C
cliquid 2.45 J/g · °C
ΔH°vap 40.5 kJ/mol

Answer 1

When no phase change is involved, use this equation.
q = mass x specific heat x (Tfinal-Tinitial).

When a phase change is involved (at the melting point or boiling point) use this one.
q = mass x heat fusion or heat vap

Total q = sum of individual qs.