Question

What is the energy change that will occur when 25.5 grams of oxygen gas (O2) react with excess methane (CH4) according to the reaction below?

CH4 + 2 O2 yields CO2 + 2 H2O deltaH = -889 kJ/mol

Answer 1

a) 354 kJ of energy will be given off by the reaction
b) 354 kJ of energy will be absorbed by the reaction
c) 708 kJ of energy will be given off by the reaction
d) 708 kJ of energy will be absorbed by the reaction

Answer 2

Anyone?

Answer 3

The reaction as it is written is telling you that 2 mole of O2 will be have a deltaH = -889 kJ/mol.
You have to calculate how many moles of O2 are in 25.5 grams of oxygen gas (O2).
then you can use the conversion factor -889 kJ/mol = 2 mole of O2 and multiply the number of moles of O2 that are in 25.5 grams by this conversion factor

Answer 4

The hint is EXCESS Methane (CH4) so that means right away that your limiting reagent is going to be oxygen.

Answer 5

The sign (-) or (+) in the value of the delta H will tell you if the reaction is giving or absorbing energy respectively.