Question

Which of the following statements are FALSE, given the following bond dissociation energies? Assume that bond energies accurately determine heats of reaction. Choose all that are false.

BE[H-H] = 436.4 kJ/mol

BE[H-N] = 393 kJ/mol

BE[H-O] = 460. kJ/mol

BE[O=O] = 498.7 kJ/mol

Question 1 options:

ΔH°f[H2O(g)] = -234 kJ/mol

ΔH°f[H(g)] = 436.4 kJ/mol

ΔH°[H2O(g) → 2 H(g) + O(g)] =920. kJ/mol

An H-H bond is stronger than an H-O bond.

NH(g) + H2(g) → NH2(g) + H(g) is an endothermic reaction.

Answer 1

PART 1:

Given reaction:

Enthalpy of the reaction is given by,

SO OPTION (a) is INCORRECT

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PART 2:

For the reaction:

Enthalpy of the reaction is given by,

SO OPTION (b) is CORRECT

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PART 3:

For the reaction:

Enthalpy of the reaction is given by,

SO OPTION (c) IS CORRECT

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PART 4:

We know that, Bond energy is directly proportional to the bond strength.

Given that,

BE[H-H] = 436.4 kJ/mol.

BE[H-O] = 460. kJ/mol.

From the given data, BE[H-O] > BE[H-H].

Therefore, H-O bond is stronger than an H-H bond.

Therefore, option (d) is INCORRECT

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PART 5:

For the reaction:

Enthalpy of the reaction is given by,

Since, sign of enthalpy is positive the reaction is endothermic.

SO OPTION (e) IS INCORRECT