What is the change in enthalpy (ΔH) for the reaction: 2H2(g) + O2(g) → 2H2O(g) i

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Question: What is the change in enthalpy (ΔH) for the reaction: 2H2(g) + O2(g) → 2H2O(g) if the bond enthalpies are: H-H = 436 kJ/mol, O=O = 498 kJ/mol, H-O = 463 kJ/mol?

Options:

−484 kJ
−572 kJ
−572 kJ
−484 kJ

Correct Answer: −572 kJ

Solution:

ΔH = Σ(bond enthalpies of reactants) - Σ(bond enthalpies of products) = [2(436) + 498] - [4(463)] = −572 kJ.

What is the change in enthalpy (ΔH) for the reaction: 2H2(g) + O2(g) → 2H2O(g) i

Practice Questions

What is the change in enthalpy (ΔH) for the reaction: 2H2(g) + O2(g) → 2H2O(g) if the bond enthalpies are: H-H = 436 kJ/mol, O=O = 498 kJ/mol, H-O = 463 kJ/mol?

−484 kJ
−572 kJ
−572 kJ
−484 kJ

Questions & Step-by-Step Solutions

What is the change in enthalpy (ΔH) for the reaction: 2H2(g) + O2(g) → 2H2O(g) if the bond enthalpies are: H-H = 436 kJ/mol, O=O = 498 kJ/mol, H-O = 463 kJ/mol?

Step 1: Identify the bonds in the reactants and products. The reactants are 2H2 and O2, and the products are 2H2O.
Step 2: Count the number of each type of bond in the reactants. For 2H2, there are 2 H-H bonds. For O2, there is 1 O=O bond.
Step 3: Calculate the total bond enthalpy for the reactants. The bond enthalpy for H-H is 436 kJ/mol, and for O=O it is 498 kJ/mol. So, total for reactants = 2(436) + 498.
Step 4: Count the number of bonds in the products. For 2H2O, there are 4 H-O bonds (2 per H2O molecule).
Step 5: Calculate the total bond enthalpy for the products. The bond enthalpy for H-O is 463 kJ/mol. So, total for products = 4(463).
Step 6: Use the formula ΔH = Σ(bond enthalpies of reactants) - Σ(bond enthalpies of products) to find ΔH.
Step 7: Substitute the values: ΔH = [2(436) + 498] - [4(463)].
Step 8: Calculate the values: Reactants = 870 kJ, Products = 1852 kJ.
Step 9: Finally, calculate ΔH = 870 - 1852 = -982 kJ.

Bond Enthalpy – The energy required to break a bond between two atoms, used to calculate the change in enthalpy for a reaction.
Enthalpy Change (ΔH) – The difference in total bond enthalpies between reactants and products, indicating whether a reaction is exothermic or endothermic.
Stoichiometry in Reactions – Understanding the coefficients in a balanced chemical equation to determine the number of bonds broken and formed.

What is the change in enthalpy (ΔH) for the reaction: 2H2(g) + O2(g) → 2H2O(g) i

What’s inside this PDF?

What is the change in enthalpy (ΔH) for the reaction: 2H2(g) + O2(g) → 2H2O(g) i

Practice Questions

Questions & Step-by-Step Solutions

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