ThermochemistryHard
Question
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 is′z′ kJ ?
Options
A.(- x - y - z)kJ
B.(- z - x + 2y)kJ
C.(- x - 2y - z) kJ
D.(- x - 2y + z)kJ
Solution
From given data, we have
C + O2 → CO2 - x kJ ......(i)
H2 +
O2 → H2O - y kJ ......(ii)
CH4 + 2O2 → CO2 + H2O + z kJ ......(iii)
The required equation is
C + 2H2 →CH4 + Q
To get the requred equation, poerate (i) + 2 × (ii) - (iii)
Thus, we get
C + 2H2 → CH4 + [(-x) + (-2y) - (-z)]
Thus, heat of formation of methane is (- x - 2y = z) kJ
C + O2
H2 +
O2 CH4 + 2O2 → CO2 + H2O + z kJ ......(iii)
The required equation is
C + 2H2
To get the requred equation, poerate (i) + 2 × (ii) - (iii)
Thus, we get
C + 2H2
Thus, heat of formation of methane is (- x - 2y = z) kJ
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