Exothermic Reaction Chemistry Example 2

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Example 2

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A reaction releases 890890 kJ of heat per mole of methane burned. If 3.23.2 g of CH4\text{CH}_4 is burned (M=16 g/molM = 16\,\text{g/mol}), how much heat is released?

Solution

  1. 1
    Find the number of moles of CH4\text{CH}_4 using n=massmolar massn = \frac{\text{mass}}{\text{molar mass}}: n=3.2 g16 g/mol=0.20 moln = \frac{3.2\,\text{g}}{16\,\text{g/mol}} = 0.20\,\text{mol}
  2. 2
    The combustion of CH4\text{CH}_4 releases 890 kJ/mol890\,\text{kJ/mol}. Scale by the number of moles.
  3. 3
    Calculate total heat released: q=0.20 mol×890 kJ/mol=178 kJq = 0.20\,\text{mol} \times 890\,\text{kJ/mol} = 178\,\text{kJ}

Answer

178 kJ released178\,\text{kJ released}
The heat released scales linearly with the amount of reactant. Knowing the enthalpy change per mole allows us to calculate the energy for any quantity.

About Exothermic Reaction

A chemical reaction that releases energy (usually as heat or light) to the surroundings, resulting in an increase in surrounding temperature and a negative enthalpy.

Learn more about Exothermic Reaction →

More Exothermic Reaction Examples

Example 1 easy

Explain why burning methane ([formula]) is an exothermic reaction.

Example 3 easy

A hand warmer packet heats up when activated. Is this an exothermic or endothermic process? Explain.

Example 4 easy

A reaction mixture causes the beaker and surrounding air to become warmer. Is the reaction exothermi

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