What will be the heat of formation of methane, if the heat of combustion of carbon is '-x' KJ, heat of formation of water is '-y' KJ and heat of combustion of methane '-Z' KJ?
A
(-x - y - z)
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B
(-z - x + 2y) KJ
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C
(-x - 2y - z) KJ
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D
(-x - 2y + z) KJ
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Solution
The correct option is D
(-x - 2y + z) KJ
The given reactions are as follows: C+O2⟶CO2−xKJ−−−−−−(i)H2+12O2⟶H2O−yKJ−−−−−−(ii) CH4+2O2⟶CO2+2H2O−zKJ−−−−−−(iii)
By manipulating equations in the manner (i) + 2(ii) - (iii) we get