Calculating ΔHfθ from combustion data

1.Find ΔHfθ of ethyne C2H2 given the

following combustion data ΔHc

θ C2H2 (g) = -1300 kJmol-1

C (s) = -394 kJmol-1

H2 (g) = -286 kJmol-1

2.Find ΔHfθ of propan-1-ol C3H7OH given the

following combustion data ΔHc

θ C3H7OH (l) = -2010 kJmol-1

C (s) = -394 kJmol-1

H2 (g) = -286 kJmol-1

Ans: +226kJmol-1

Ans: -316kJmol-1

Calculating ΔHrθ from formation data

1. Calculate ΔHrθ for the following reaction:

CH2=CH2(g) + H2(g) CH3CH3(g)

ΔHfθ ethene = +52kJmol-1

ΔHfθ ethane = -85kJmol-1

2. Calculate ΔHrθ for the reaction:

CaCO3(s) CaO(s) + CO2(g)

ΔHfθ CaCO3= -1207kJmol-1

CaO = -635kJmol-1

CO2 = -394kJmol-1

Ans: -137kJmol-1

Ans: +178kJmol-1