For the following reaction,

C (diamond) + O₂ → CO₂ (g); $Δ H = - 97.6 k c a l$
C (graphite) + O₂ → CO₂ (g); $Δ H = - 94.3 k c a l$
The heat change for the conversion of 1 g of
C (diamond) → C (graphite) is:

Question

For the following reaction,

C (diamond) + O₂ → CO₂ (g); $Δ H = - 97.6 k c a l$

C (graphite) + O₂ → CO₂ (g); $Δ H = - 94.3 k c a l$

The heat change for the conversion of 1 g of

C (diamond) → C (graphite) is:

TestHub · Accepted Answer

Question Explanation:

Calculating the heat change for the conversion of diamond to graphite per gram.

Concept:

Hess's Law of Constant Heat Summation

Solution:

The enthalpy of conversion from diamond to graphite is obtained by subtracting the combustion enthalpy of graphite from that of diamond. The result is then converted from a per-mole basis to a per-gram basis using the molar mass of carbon.

$C ($ diamond $) + O_{2} \to CO_{2}; Δ H_{1} = - 97.6 kcal . C ($ graphite $) + O_{2} \to CO_{2}; Δ H_{2} = - 94.3 kcal$ .

For $C ($ diamond $) \to C ($ graphite $) : Δ H = Δ H_{1} - Δ H_{2} = - 97.6 - (- 94.3)$ $= - 3.3 kcal / mol$ .

Heat change for $1 g = \frac{3.3 kcal}{12 g} = 0.275 kcal$ .

Final Answer: 0.275 kcal

Chemistry - Thermochemistry Question with Solution | TestHub

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