Enthalpy Changes in Chemical Reactions

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What is the enthalpy change of a reaction (∆Hr)?

Back

The heat energy released or absorbed in a chemical reaction.

Front

What is the formula for calculating the enthalpy change of a reaction (∆Hr)?

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∆Hr = ∑ ∆H°f (products) - ∑ ∆H°f (reactants)

Front

What is the standard enthalpy change of formation (∆H°f)?

Back

Heat change when 1 mole of a substance is formed from its elements under standard conditions.

Front

Provide an example of standard enthalpy change of formation (∆H°f).

Back

Mg(s) + 1/2 O2(g) → MgO(s)

Front

What is the standard enthalpy change of combustion (∆H°c)?

Back

Heat released when 1 mole of a substance is completely burnt in excess oxygen under standard conditions.

Front

Provide an example of standard enthalpy change of combustion (∆H°c).

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C3H6(g) + 9/2 O2(g) → 3CO2(g) + 3H2O(ℓ)

Front

What is the standard enthalpy change of hydration (∆H°hyd)?

Back

Heat released when 1 mole of a gaseous ion dissolves in water to form hydrated ions under standard conditions.

Front

Provide an example of standard enthalpy change of hydration (∆H°hyd).

Back

Na+(g) → Na+(aq)

Front

What is the standard enthalpy change of solution (∆H°soln)?

Back

Heat change when 1 mole of a substance dissolves in water to form a solution at infinite dilution under standard conditions.

Front

Provide an example of standard enthalpy change of solution (∆H°soln).

Back

NaOH(s) → Na+(aq) + OH-(aq)