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26/09/2021 12:07 pm
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Calculate the heat produced (in kJ) when 224 g of CaO is completely converted to CaCO3 by reaction with CO2 at 27°C in a container of fixed volume.
Given : ΔH°f (CaCO3,s) = -1207 kJ/mol;
ΔH°f (CaO,s) = -635 kJ/mol, ΔH°f (CO2, g) = -394 kJ/mol; [Use R = 8.3 JK–1 mol–1]
(a) 702.04 kJ
(b) 721.96 kJ
(c) 712 kJ
(d) 721 kJ
1 Answer
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26/09/2021 12:16 pm
Correct answer: (a) 702.04 kJ
Explanation:
CaO(s) + CO2 → CaCO3
ΔH°f = ΔH°f (CaCO3) - ΔH°f (CaO) - ΔH°f (CaCO2)
= -1207 - (-635) - (-394)
= -178 kJ/mol
∴ ΔU = ΔH - ΔngRT
ΔU = -178 - \(\Big(\frac{(-1) \times 8.3 \times 300}{1000}\Big)\)
= -175.51 kJ
nCaO = \(\frac{224}{56}\) = 4
∴ qv = nΔfU = 4 x (-175.51)
= - 702.04 kJ