Formation Equations Video Lessons

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# Problem: For the reaction,2H2 (g) + O2 (g) → 2H2O(g) ΔH = -484 kJwhich of the following is true?(a) The ΔHf° for H2O(g) is -484 kJ/mole.(b) All reactants and products are in their standard state.(c) The reaction is exothermic.(d) The ΔHf° for H2O(ℓ) would be less negative.(e) You would need ΔH f° (H2) to calculate ΔH f° (O2).

###### FREE Expert Solution

We are asked which of the following is true for the reaction:
2H2 (g) + O2 (g) → 2H2O(g) ΔH = -484 kJ

Analyze each statement:

(a) The ΔHf° for H2O(g) is -484 kJ/mole.

• -484 kJ/mole is the standard enthalpy change of reaction (ΔHrxn°) not the enthalpy of formation of water (Hf° for H2O(g)).
• FALSE

(b) All reactants and products are in their standard state.

• H2O(g) is not a standard state
• FALSE

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###### Problem Details

For the reaction,
2H2 (g) + O2 (g) → 2H2O(g) ΔH = -484 kJ
which of the following is true?

(a) The ΔHf° for H2O(g) is -484 kJ/mole.

(b) All reactants and products are in their standard state.

(c) The reaction is exothermic.

(d) The ΔHf° for H2O(ℓ) would be less negative.

(e) You would need ΔH f° (H2) to calculate ΔH f° (O2).