By convention, exothermic reactions have a _________ heat of reaction

Chemistry
1

by convention, exothermic reactions have a _________ heat of reaction.

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By convention, exothermic reactions have a _________ heat of reaction

Answer: By convention, exothermic reactions have a negative heat of reaction.

  1. Understanding Exothermic Reactions

    • In chemistry, exothermic reactions are chemical reactions that release energy in the form of heat, light, or both. This release of energy indicates that the products contain less energy than the reactants.

  2. Heat of Reaction (ΔH)

    • The heat of reaction, also known as enthalpy change (ΔH), is the difference in enthalpy between the products and the reactants. It is an indicator of the overall energy change during a chemical reaction.

      \Delta H = H_{products} - H_{reactants}

  3. Sign Convention for ΔH

    • According to thermodynamic conventions, the heat of reaction for exothermic reactions is negative. This is because the system loses energy to the surroundings, leading to a decrease in the enthalpy of the system.

  4. Thermodynamics and Energy Flow

    • In an exothermic reaction, the total energy of the products is lower than that of the reactants. The excess energy is released to the surroundings.

    • For example, during the combustion of methane (CH₄):

      CH_4 + 2O_2 \rightarrow CO_2 + 2H_2O \hspace{10mm} \Delta H < 0

      This reaction releases energy, which can be observed as heat and light, and has a negative ΔH value.

Final Answer:
By convention, exothermic reactions have a negative heat of reaction.