Use the following equation for the combustion of methane to answer the following questions:
CH4 + 2O2 -> CO2 +2 H2O ΔH = -900 kJ

a. Is the reaction exothermic or endothermic?

b. If you burn 2 moles of methane, how much energy is released?

c. If you burn 48 g of methane, how much energy is released?

a) Reaction is exothermic

b) 1800 kj

c) 2700 kj

Explanation:

Chemical reaction:

CH₄ + 2O₂    →   CO₂ + 2H₂O       ΔH = -900 KJ

Is the reaction exothermic or endothermic?

Reaction is exothermic because heat is released.

Exothermic reaction:

The type of reactions in which energy is released are called exothermic reactions.

In this type of reaction energy needed to break the bonds are less than the energy released during the bond formation.

For example:

Chemical equation:

C + O₂   →  CO₂    ΔH = -393 Kj/mol

it can be written as,

C + O₂   →  CO₂ + 393 Kj/mol

b. If you burn 2 moles of methane, how much energy is released?

One mole of CH₄  burn it produces 900 kj energy.

2 mol × 900 kj = 1800 kj

c. If you burn 48 g of methane, how much energy is released?

Now we will convert the mass into moles.

Number of moles = mass / molar mass

Number of moles = 48 g/  16 g/mol

Number of moles = 3 mol

Energy produced by 3 moles:

3 mol × 900 kj = 2700 kj