heat of combustion...

BITSAT 2015 Sample Questions › Physical Chemistry questions › heat of combustion...

the heats of combustion of C2H4 , C2H6 AND H2 are -1400.5Kj,-1558.3kj and -286.5kj. the heat of hydrogenation of ethene is..
pleaz solve lucidly

#Chemistry #Physical Chemistry

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5 Answers

11

Tush Watts ·2010-05-20 11:11:05

Ans) - 2671.8 KJ ?

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dinks007 ·2010-05-20 12:25:59

sorry thats not the answer.....

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Manmay kumar Mohanty ·2010-05-21 00:10:58

- 157.8 KJ ??

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Manmay kumar Mohanty ·2010-05-21 00:35:39

i must be like this i guess if correct

2C + 2H₂ â†’ C₂H₄ - 1400.5 KJ
2C + 3H₂ â†’ C₂H₆ - 1558.3 KJ

C₂H₄ â†’ 2C + 2H₂ 1400.5 KJ .............(1)
2C + 3H₂ â†’ C₂H₆ - 1558.3 KJ .............(2)
Solving (1) and (2) we get

= C₂H₄ + H₂ â†’ C₂H₆ - 157.8 KJ

NOt sure if correct ?

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rahul1993 Duggal ·2010-06-11 04:08:07

using Hess's law we can write the foolowing eqns

C₂H₄ + 3O₂ â†’ 2CO₂ + 2H₂0 Î”H=-1400.5 KJ/mol

3H₂O + 2CO₂ â†’ C₂H₆ + 7/2O₂ Î”H= 1558.3 Kj/mol

H₂ + 1/2O₂ â†’ H₂O Î”H=-286.5 Kj/mol

adding the above, we get req eqn and Î”HÂ°_H = -128.7 KJ/mol

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