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Lecture 7 Thermo chemistry: illustration
Content:
Illustration‐i Do yourself‐i Illustration‐ii Do yourself‐ii Illustration‐iii Do yourself‐iii Illustration‐iv
Illustration‐ i
Calculate heat of the following reaction/ mole at 550K.
ZnOሺSሻ CሺSሻ ൌ Znሺgሻ COሺgሻ
Given:
Component H 1500 ‐H 298 (kcal/kg mol)
∆H °
(kcal/kg mol) ZnO(s) C(s) Zn(g) CO(g)
For the reaction 1
൫∆H (^) °^ ൯ଶଽ଼ ൌ ൫∆H (^) °^ ൯CO െ ൫∆H (^) °^ ൯Z୬O
Substituting the values we get
൫∆H (^) °^ ൯ଶଽ଼ ൌ 54150 k cal/kg mol.
ሺ∆H (^) ሻଵହ ൌ ൫∆H (^) °^ ൯ଶଽ଼ ∑ሺHଵହ െ H (^) ଶଽ଼ ሻ (^) ୮୰୭ୢ୳ୡ୲ୱ െ ∑ሺHଵହ െ H (^) ଶଽ଼ ሻ (^) ୰ୣୟୡ୲ୟ୬୲
Substituting the value we get
ሺ∆H (^) ሻଵହ ൌ 72689 kcal/kg mol
Do you self –i
Calculate heat of the following reaction at 1200K.
Feଶ O (^) ଷ 3CO ൌ 2Fe 3CO (^) ଶ
Component H 1200 ‐H 298 (kcal/kg mol)
∆H °
(kcal/kg mol) Fe 2 O 3 CO CO 2 Fe
Illustration –ii
Calculate heat content in 1 kg mol nickel at 3500Ԩ.
At 3500Ԩ ሺNiሻ^ ୱ ൌ NiሺVሻ.
Nickel undergoes phase transformation from α to β at360Ԩ.
Melting point of Ni ൌ 1455Ԩ, boiling point is 2730Ԩ
Latent heat of melting ൌ 4248 (^) ୩ ୫୭୪୩ୡୟ୪
Latent heat of vaporization ൌ 87910 kcal/kg mol
ሺC (^) P ሻ (^) N୧ α ൌ 12.535 ሺ35.815 ൈ 10ି ଷ^ Tሻ െ ሺ6.95x10ହ^ Tି ଶ^ ሻ (^) ୩ ୫୭୪ୣ KKJ
ሺCP ሻ (^) N୧ β ൌ 25.104 ሺ7.531 ൈ 10ି ଷ^ Tሻ െ (^) ୩ ୫୭୪ୣ KKJ
Latent heat of transformation from α to β ൌ 0
Solution
Heat content in 1 kg mol nickel vapour
݂ ݅ܰ ݊݅ ݐ݊݁ݐ݊ ܿ ݐܽ݁ܪሺ 25 ݉ݎԨ 360 ݐԨሻ ሺlatent heat of transformationሻ ሺHeat content in Ni from 360Ԩto 1455Ԩሻ ሺlatent heat of meltingሻ ሺHeat content in Ni from 1455Ԩto 2730Ԩሻ ሺlatent heat of vaprizationሻ ሺHeat content in Ni from 2730Ԩto 3500Ԩሻ
One has to calculate all the values to give heat content ൌ 119217.5 (^) ୩ ୫୭୪୩ୡୟ୪ in Ni vapour at 3500Ԩ
which is equal to (^2020) ୩ N୧୩ ୡୟ୪
Do yourself – ii
For a solid silver, the molar heat capacity at constant pressure
C (^) P ൌ 21.3 ሺ8.535 ൈ 10ି ଷ^ Tሻ ሺ1.506 ൈ 10ହ^ Tି ଷ^ ሻJ/g mol k
Illustration iv
Calculate heat of reaction at 1100Ԩ
Cuଶ Sሺsሻ ሺO (^) ଶ 3.76 N (^) ଶ ሻ (^) ൌ 2Cuሺlሻ SO (^) ଶ ሺgሻ 3.76N (^) ଶ ሺgሻ
Reactants and products are at 1100Ԩ. Air is supplied at 25Ԩ. Melting point of copper is 1084Ԩ.
C (^) P ሺCuଶ sሻ ൌ 81.588 (^) ୫୭୪ ୩.J
CP ሺCuୱ୭୪୧ୢ ሻ ൌ 22.635 ሺ6.27 ൈ 10ି ଷ^ Tሻ^ ୫୭୪ ୩J.
CP ൫Cu୪୧୯୳୧ୢ ൯ ൌ 31.380 (^) ୫୭୪ ୩୨
CP ሺSO (^) ଶ ሻ ൌ 43.430 ሺ10.62 ൈ 10ି ଷ^ Tሻ െ ሺ3.766 ൈ 10ହ^ Tି ଶ^ ሻ
CP ሺN (^) ଶ ሻ ൌ 27.865 ሺ4.268 ൈ 10ି ଷ^ Tሻ
Latent heat of copper ൌ 11193 (^) ୫୭୪୨
൫∆H C୳°^ మ ୱ൯ଶଽ଼ ൌ െ79496 ୫୭୪୨ , ∆H SO°^ మൌ െ296810 ୫୭୪୨
∆H R ሺ1373ሻ ൌ ∆H R°^ ∑ሺHଵଷଷ െ H ଶଽ଼ ሻ P െ ∑ሺHଵଷଷ െ H ଶଽ଼ ሻ R
On solving ∆H (^) R ሺ1373ሻ ൌ െ40405 joule
