Define and explain the term, enthalpy or heat of reaction.

1.	Define and explain the term, enthalpy or heat of reaction.
Answer» Enthalpy or heat of reaction : The enthalpy of a chemical reaction is the difference between the sum of the enthalpies of products and that of the reactants with every substance in a definite physical state and in the amounts (moles) represented by the coefficients in the balanced equation. Explanation : Consider the following general reaction, aA + bB → cC + dD The heat of the reaction ΔH is the difference in sum of enthalpies of products and sum of enthalpies of reactants. ∴ ΔH = ΣH_produts – ΣH_reactants = [cH_c + dH_D] – [aH_A + bH_B] = Σ_PH – Σ_RZ Where H represents enthalpy of the substance. For endothermic reaction, ΔH is positive, (ΔH > 0). For exothermic reaction, ΔH is negative, (ΔH < 0).

Answer»

Enthalpy or heat of reaction : The enthalpy of a chemical reaction is the difference between the sum of the enthalpies of products and that of the reactants with every substance in a definite physical state and in the amounts (moles) represented by the coefficients in the balanced equation.

Explanation : Consider the following general reaction,

aA + bB → cC + dD

The heat of the reaction ΔH is the difference in sum of enthalpies of products and sum of enthalpies of reactants.

∴ ΔH = ΣH_produts – ΣH_reactants

= [cH_c + dH_D] – [aH_A + bH_B]

= Σ_PH – Σ_RZ

Where H represents enthalpy of the substance. For endothermic reaction,

ΔH is positive, (ΔH > 0).

For exothermic reaction,

ΔH is negative,

(ΔH < 0).

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