Question

Which statement about the following reaction is correct?

CH4 (g) + 2O2 (g) yields CO2 (g) + 2H2O(l) deltaH = -890 kJ

reacting one mole of oxygen (O2) absorbs 445 kJ of energy

reacting one mole of oxygen (O2) releases 445 kJ of energy

reacting one mole of methane (CH4) absorbs 890 kJ of energy

reacting two moles of methane (CH4) releases 890 kJ of energy

Answer 1

First off note that the reaction is exothermic which can be determined by noticing the negative enthalpy value. This means that all reactants will end up releasing energy, how much energy they will release depends on the molar amount. From this you can already eliminate two answer choices (i'll let you decide what can be eliminated at this step). You must also realize that the enthalpy value of the overall reaction is taking into account that the number of moles of CH4 = 1 and the number of moles of O2 = 2.

Answer 2

B (: Thank you for explaining it so well! Really helped! I have a couple similar questions if you could help?