Y13 Hess's law exam MC

Nitrogen dioxide is produced from ammonia and air as shown in these equations. 4 NH₃(g) + 5 O₂ (g) → 4 NO(g) + 6 H₂O(g) ΔH = –909 kJ mol⁻¹ 2 NO(g) + O₂ (g) → 2 NO₂ (g) ΔH = –115 kJ mol⁻¹ What is the enthalpy change (in kJ mol⁻¹) for the following reaction? 4 NH₃(g) + 7 O₂ (g) → 4 NO₂ (g) + 6 H₂O(g)

• –679

• –794

• –1024

• –1139

Which reaction has an enthalpy change equal to the standard enthalpy of formation of silver iodide?

• Ag(g) + ½I₂(g) → AgI(s)

• Ag(s) + ½I₂(s) → AgI(s)

• Ag⁺(g) + I⁻(g) → AgI(s)

• Ag⁺(aq) + I⁻(aq) → AgI(s)

Two reactions of iron with oxygen are shown.

Fe(s) + ½ O₂(g) → FeO(s) ΔH = –272 kJ mol⁻¹ 2 Fe(s) + 3/2 O₂(g) → Fe₂O₃(s) ΔH = –822 kJ mol⁻¹ What is the enthalpy change, in kJ mol⁻¹, for this reaction? 2 FeO(s) + ½ O₂(g) → Fe₂O₃(s)

• +550

• –278

• –1094

• –1372

Use the information below to answer this question. C(s) + O₂(g) → CO₂(g) ΔH° = –394 kJ mol⁻¹ H₂(g) + 1/2 O₂(g) → H₂O(l) ΔH° = –286 kJ mol⁻¹ 4C(s) + 5H₂(g) → C₄H₁₀(g) ΔH° = –126 kJ mol⁻¹ The standard enthalpy of combustion of butane, in kJ mol⁻¹, is

• –2880

• –2590

• –806

• –554

Use the information below to answer this question. C(s) + O₂(g) → CO₂(g) ΔH° = -393.5 kJ mol⁻¹ H₂(g) + ½ O₂(g) → H₂O(l) ΔH° = -285.8 kJ mol⁻¹ 3 C(s) + 4 H₂(g) → C₃H₈(g) ΔH° = -104.0 kJ mol⁻¹ 4 C(s) + 5 H₂(g) → C₄H₁₀(g) ΔH° = -125.2 kJ mol⁻¹ The value in kJ mol⁻¹ for the enthalpy of combustion of propane is

• -211.7

• -419.7

• -2220

• -2878

The table shows the standard enthalpy of formation, Δf​H^θ, for some of the substances in the reaction

C₂H₆(g) + 6 F₂(g) ⟶ C₂F₆(g) + 6 HF(g)   Δf​H^θ = −2898 kJ mol⁻¹

What is the standard enthalpy of formation, in kJ mol–1, for HF(g)?

• –1638

• –273

• +273

• +1638

Using the information in the table, answer this question.

Fe₂O₃(s) + 3 H₂(g) → 2 Fe(s) + 3 H₂O(g) ΔH^θ = +96 kJ mol⁻¹

The standard enthalpy of formation of steam is

• +286 kJ mol⁻¹

• +242 kJ mol⁻¹

• -242 kJ mol⁻¹

• -286 kJ mol⁻¹

This question is about the reaction given below.

CO(g) + H₂O(g) ⇌ CO₂(g) + H₂(g)

Enthalpy data for the reacting species are given in the table.

The standard enthalpy change for this reaction of carbon monoxide and steam is:

• A. +42 kJ mol⁻¹

• B. -42 kJ mol⁻¹

• C. +262 kJ mol⁻¹

• D. -262 kJ mol⁻¹

The table shows data for the four hydrocarbons ethyne, propyne, propene and propane. ΔH_c^θ is the standard enthalpy of combustion of these hydrocarbons. The complete combustion of 2.0 g of one of the above hydrocarbons releases exactly 100 kJ of heat energy. This hydrocarbon is:

• ethyne

• propyne

• propene

• propane

Calculate the enthalpy change, in kJ, for this dissociation of mole of propan-1-ol.

C₃H₇OH(g) → 3 C(g) + 8 H(g) + O(g)

Mean bond dissociation enthalpy / kJ mol⁻¹: C–H: 412, C–C: 348, C–O: 360, O–H: 463

• –4751

• –4403

• +4403

• +4751