Chemistry - Thermochemistry Question with Solution | TestHub
In some regions natural gas is converted into 'synthesis gas' for industrial use by the steam reforming reaction:
CH4(g) + H2O(g) → CO(g) + 3H2(g)
Assume the methane is 100% pure. Given ΔHC (kcal/mol) at 25°C: H2(g) = -68.0; CO(g) = -67.6; CH4(g) = -212.8. Select the correct option(s): (one or more than one correct)
Options:(select one or more)
Answer:
Solution:
1.6 kg CH₄ = 1600/16 = 100 mol.
(a) 100 × 212.8 = 21,280 kcal, not 27,160 kcal (false).
(b) Each mole of CH₄ gives 1 mole of CO + 3 moles of H₂, which burn to give 67.6 + 3(68.0) = 271.6 kcal. Therefore, 100 × 271.6 = 27,160 kcal (true).
(c) One mole of CH₄-derived gas (CO + 3H₂) has a mass of 28 + 6 = 34 g. Thus, 1700 g = 50 mol, which gives 50 × 271.6 = 13,580 kcal (true).
(d) For 1.6 kg of methane, the heat produced is 21,280 kcal. However, the gas derived from it releases 27,160 kcal, and 1.6 kg of the derived gas releases a different amount again. Therefore, these amounts are not equal (false).
The correct answers are (b) and (c).
