Question

Enter your answer in the provided box. Diamond and graphite are two crystalline forms of carbon. At 1 atm and 25°C, diamond changes to graphite so slowly that the enthalpy change of the process must be obtained indirectly. Determine ΔHrxn for C(diamond) → C(graphite) with equations from the following list: (1) C(diamond) + O2(g) → CO2(g) ΔH = −395.4 kJ (2) 2 CO2(g) → 2 CO(g) + O2(g) ΔH = 566.0 kJ (3) C(graphite) + O2(g) → CO2(g) ΔH = −393.5 kJ (4) 2 CO(g) → C(graphite) + CO2(g) ΔH = −172.5 kJ

Answer 1

Answer:

ΔHrxn = -1.9kJ

Explanation:

Considering the 3 elementary equations

Cancelling out O2 From equation 1 reactant and equation 2 product,

Also

Cancelling out CO2 From equation 1 and 3 product and equation 2 reactant..

Finally

Cancelling out 2CO From equation 2 product and 2CO from equation 3 reactant..

This will give us an overall equation that is due to arithmetic addition of equation 1,2&3

Hence

C(diamond) → C(graphite)

ΔHrxn= -395.4+566.0-172.5 = -1.9kJ

ΔHrxn = -1.9kJ