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

The statement about the following reaction "CH4 (g) + 2O2 (g) yields CO2 (g) + 2H2O(l) deltaH = -890 kJ" is correct is reacting one mole of oxygen (O2) releases 445 kJ of energy. Since by reacting with two mole of oxygen, you will get a release of energy of -890kJ so if only one mole of oxygen is to be reacted, you will get -445 kJ of energy.

Answer 2

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

Explanation: Exothermic reactions are defined as the reactions in which energy is released in the form of heat and
`\Delta H` for the reaction comes out to be negative.

`CH_4+2O_2\rightarrow CO_2+2H_2O`
`\Delta H=-890kJ`

According to the given balanced equation:

1 mole of methane reacts with 2 moles of oxygen and 890 kJ of energy is released.

Thus when the reaction is halved, the enthalpy also gets halved.

Thus
`(1)/(2)CH_4+O_2\rightarrow (1)/(2)CO_2+H_2O`
`\Delta H=-445kJ`

Now half mole of methane reacts with 1 mole of oxygen and 445 kJ of energy is released.