In the presence of excess oxygen, methane gas burns in a constant pressure system to yield carbon dioxide and water: (g) + (g) → (g) + O (l) H = -890.0 kJ Calculate the value of q (kJ) in this exothermic reaction when 1.90 g of methane is combusted at constant pressure.

Question

In the presence of excess oxygen, methane gas burns in a constant pressure system to yield carbon dioxide and water:  (g) +  (g) →  (g) +  O (l)  H = -890.0 kJ Calculate the value of q (kJ) in this exothermic reaction when 1.90 g of methane is combusted at constant pressure.

Quizplus · Accepted Answer

We need to use the formula q = nΔH, where n is the number of moles of methane, and ΔH is the enthalpy change of the reaction.

First, we need to determine the number of moles of methane that reacted. We can use the molar mass of methane to convert the given mass to moles:

1.90 g CH4 × (1 mol CH4/16.05 g CH4) = 0.118 mol CH4

Now we can use the given enthalpy change to calculate q:

q = (0.118 mol CH4)(-890.0 kJ/mol) = -105.22 kJ

Rounding to the nearest whole number, we get q = -106 kJ, which is answer choice E.

In the Presence of Excess Oxygen, Methane Gas Burns in a Constant