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Question: \[C_{(\text{diamond})} + O_{2}(g) \rightarrow CO_{2}(g);\Delta H = - 395kJ\] \[C_{(g\text{raphite})...

C(diamond)+O2(g)→CO2(g);ΔH=−395kJC_{(\text{diamond})} + O_{2}(g) \rightarrow CO_{2}(g);\Delta H = - 395kJ

C(graphite)+O2(g)→CO2(g);ΔH=−393.5kJC_{(g\text{raphite})} + O_{2}(g) \rightarrow CO_{2}(g);\Delta H = - 393.5kJ

From the data, the ΔH\Delta H when diamond is formed from graphite is

A

–1.5Kj

B
  • 1.5kJ
C

+3.0kJ

D

–3.0kJ

Answer
  • 1.5kJ
Explanation

Solution

C(graphite)→C(diamond)C_{(\text{graphite})} \rightarrow C_{(\text{diamond})}

ΔH(diamond)=−395kJ\mathbf{\Delta}\mathbf{H}_{\mathbf{(}\text{diamond}\mathbf{)}}\mathbf{= - 395kJ}; ΔH(graphite)=−393.5kJ,\mathbf{\Delta}\mathbf{H}_{\mathbf{(}\text{graphite}\mathbf{)}}\mathbf{=}\mathbf{-}\mathbf{393.5kJ,}

ΔH=ΔHgraphite\mathbf{\Delta H = \Delta}\mathbf{H}_{\text{graphite}}– ΔHdiamond\mathbf{\Delta}\mathbf{H}_{\text{diamond}}=–393.5−(−395.0)\mathbf{393.5}\mathbf{-}\mathbf{(}\mathbf{-}\mathbf{395.0)}

ΔH\mathbf{\Delta H} = +1.5kJ\mathbf{+ 1.5kJ}