In the presence of excess oxygen, methane gas burns in a constant-pressure system to yield carbon dioxide and water: ch4 (g) 2o2 (g) → co2 (g) 2h2o(l) δh = -890.0 kj
calculate the value of q (kj) in this exothermic reaction when 1.70 g of methane is combusted at constant pressure.
(a) -94.6 kj
(b) 0.0306 kj
(c) -0.0106 kj
(d) 32.7 kj
(e) -9.46 × 10^4 kj

The energy released will be -94.56 kJ or -94.6 kJ.

Explanation:

The molar mass of methane is 16g/mol

The given reaction is:

the enthalpy of reaction is given as  ΔH = -890.0 kJ

This means that when one mole of methane undergoes combustion it gives this much of energy.

Now as given that the amount of methane combusted = 1.70g

The energy released will be:

a. energy is absorbed in the reaction.

if in a given reaction the energy of products is greater than the energy of reactants it means that reaction is endothermic and during the reaction, the energy is absorbed by reactants. in an endothermic reaction, the products have more stored chemical energy than the reactants. and in this reaction the reactants are more stable than products before the compounds with less energy are always more stable.