Standard molar heats of formation of Qobr (kJ / mol) of methane (74.9), СО (110), О2 (0) and water (285.8) are known. Calculate the thermal effect of the incomplete combustion reaction of 1 mol of methane to carbon monoxide (II).
We write the equation of the reaction of incomplete combustion of methane.
2CH4 + 3O2 = 2CO + 4H2O + Q
According to Hess law, the heat of a chemical reaction (Q reaction) is equal to the difference between the sum of the heats of formation of the reaction products and the sum of the heats of formation of the starting materials:
Q reactions = ΣQ sample (products) – ΣQ sample (raw materials)
Substituting the initial data in this formula, we obtain:
Qreactions = 2Qr (CO) + 4Qr (H2O) – 2Qr (CH4) – 3Qr (O2) = 2 · 110 + 4 · 285.8 – 2 · 74.9 – 0 = 1213.4 kJ.
Answer: Qreactions = 1213.4 kJ.
Remember: The process of learning a person lasts a lifetime. The value of the same knowledge for different people may be different, it is determined by their individual characteristics and needs. Therefore, knowledge is always needed at any age and position.