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in Chemistry by kratos

Calculate the standard enthalpy of the reaction, 2C(graphite) + 3H2(g) →C2H6(g) ; ΔH° = ?

from the following ΔH° values:

a. C2H6(g) + (\frac72)O2(g) → 2CO2(g) + 3H2O(l) ; ΔH° = –1560 kJ

b. H2(g) + (\frac12) O2(g) → H2O(l) ; ΔH° = –285.8 kJ

c. C(graphite) + O2(g) → CO2(g) ; ΔH° = –393.5 kJ.

1 Answer

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by kratos
 
Best answer

Given: Given equations are,

a. C2H6(g) + (\frac72)O2(g) → 2CO2(g) + 3H2O(l), ΔH° = –1560 kJ .......(1)

b. H2(g) + (\frac12) O2(g) → H2O(l),ΔH° = –285.8 kJ ........(2)

c. C(graphite) + O2(g) → CO2(g),ΔH° = –393.5 kJ. .........(3)

To find: Standard enthalpy of the given reaction

Calculation: Reversing equation (1),

2CO2(g) + 3H2O(l) → C2H6(g) + (\frac72)O2(g), ΔH° = –1560 kJ .......(4)

Multiplying equation (2) by 3 and (3) by 2, then adding to equation (4)

ΔH° = 1560 + (-857.4) + (-787.0) = -84.4 kJ

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