Module 2: Born Haber Cycles

• Find the standard enthalpy of formation of ethane. Given the following enthalpies of combustion;

• C(s) = -393 KJ mol-1

• H2(g)= -286 KJ mol-1

• C2H6(g) = -1560 KJ mol-1

Step 1: Write equations for the data provided

• C(s) + O2 CO2(g)

• H2(g)+ ½ O2(g) H2O(l)

• C2H6(g) + 7/2 O2 2CO2(g) + 3H2O(l)

• 2C(s)+ 3H2(g) C2H6(g)

• Start your cycle with the left hand side of this equation.

Step 2: Write an equation for what you

want to find.

Step 3: The Cycle

2C(s) + 3H2(g)

2CO2(g) +3H2(g)

2CO2(g) +3H2O(l)

C2H6(g)2Hc[C]

3Hc[H2]

Hc[C2H6]

Hf[C2H6]

Step 4: Calculation

Hf[C2H6(g)] =

2(-393) + 3(-286) + (1560)

= -84 KJ mol-1