IB Chemistry Quiz: Apply Energy Cycles In Reactions

The combustion of hydrazine, N₂H₄(g), is a highly exothermic reaction used in rocket fuel: N₂H₄(g) + O₂(g) → N₂(g) + 2H₂O(g), ΔH = -579 kJ mol⁻¹. Given the average bond enthalpies N-N (160 kJ mol⁻¹), N-H (391 kJ mol⁻¹), O=O (498 kJ mol⁻¹), and O-H (464 kJ mol⁻¹), what is the bond enthalpy of the N≡N bond in gaseous nitrogen?

Given the following thermochemical equations: C(s) + 2H₂(g) → CH₄(g) ΔH₁ C(s) + O₂(g) → CO₂(g) ΔH₂ H₂(g) + ½O₂(g) → H₂O(l) ΔH₃ What is the correct expression for the standard enthalpy of combustion of methane, CH₄(g) + 2O₂(g) → CO₂(g) + 2H₂O(l)?

Using the following standard enthalpies of formation, ΔH_f⦵, what is the standard enthalpy change for the hydrogenation of ethyne? C₂H₂(g) + 2H₂(g) → C₂H₆(g) ΔH_f⦵(C₂H₂(g)) = +227 kJ mol⁻¹ ΔH_f⦵(C₂H₆(g)) = -85 kJ mol⁻¹

Given the following standard enthalpies of combustion, ΔH_c⦵, what is the standard enthalpy of formation for propane, C₃H₈(g), according to the equation 3C(s) + 4H₂(g) → C₃H₈(g)? ΔH_c⦵(C(graphite)) = -394 kJ mol⁻¹ ΔH_c⦵(H₂(g)) = -286 kJ mol⁻¹ ΔH_c⦵(C₃H₈(g)) = -2220 kJ mol⁻¹

Ethene, C₂H₄(g), reacts with bromine, Br₂(g), to form 1,2-dibromoethane, C₂H₄Br₂(g). Using the average bond enthalpies below, estimate the enthalpy change for this reaction. Bond Enthalpies (kJ mol⁻¹): C=C (614), Br-Br (193), C-C (346), C-Br (285).

The incomplete combustion of carbon produces carbon monoxide: C(s) + ½O₂(g) → CO(g). Determine the standard enthalpy change for this reaction using the following data: Standard enthalpy of combustion of C(s) = -393.5 kJ mol⁻¹ Standard enthalpy of combustion of CO(g) = -283.0 kJ mol⁻¹

An energy cycle relates the enthalpy of formation of methane (ΔH₁), the enthalpy of atomization of solid carbon (ΔH₂), and the bond enthalpy of H-H (ΔH₃). The cycle shows that C(s) and 2H₂(g) can form C(g) and 4H(g), which then form CH₄(g). Which expression represents the total energy required to break all bonds in one mole of methane, CH₄(g) → C(g) + 4H(g)?

A key step in the Ostwald process for producing nitric acid is the oxidation of ammonia: 4NH₃(g) + 5O₂(g) → 4NO(g) + 6H₂O(g), ΔH⦵ = -905 kJ. Given ΔH_f⦵(NH₃(g)) = -46 kJ mol⁻¹ and ΔH_f⦵(H₂O(g)) = -242 kJ mol⁻¹, what is the standard enthalpy of formation of nitrogen monoxide, NO(g), in kJ mol⁻¹?

Using the data below, what is the lattice enthalpy (for the dissociation of the solid into gaseous ions) of potassium oxide, K₂O, in kJ mol⁻¹? Enthalpy of formation of K₂O(s): -361 Enthalpy of atomization of K(s): +89 First ionization energy of K(g): +419 Enthalpy of atomization of O(g) from ½O₂(g): +249 First electron affinity of O(g): -141 Second electron affinity of O(g): +798

The standard enthalpy of combustion of graphite is -393.5 kJ mol⁻¹ and that of diamond is -395.4 kJ mol⁻¹. What is the enthalpy change for the allotropic conversion of one mole of diamond to graphite? C(diamond, s) → C(graphite, s)

The enthalpy change for H₂(g) + Cl₂(g) → 2HCl(g) calculated using average bond enthalpies is -185 kJ. The experimentally determined value is -184 kJ. What is the most likely reason for this very close agreement?

The standard enthalpy of combustion for methane (CH₄(g) + 2O₂(g) → CO₂(g) + 2H₂O(g)) is experimentally determined to be -890 kJ mol⁻¹. A calculation using average bond enthalpies yields a value of -818 kJ mol⁻¹. Which statement best explains this discrepancy?

The standard enthalpy change for the combustion of carbon monoxide, 2CO(g) + O₂(g) → 2CO₂(g), is -566 kJ. The standard enthalpy of formation of carbon dioxide, CO₂(g), is -394 kJ mol⁻¹. What is the standard enthalpy of formation, ΔH_f⦵, of carbon monoxide, CO(g)?

In a thermochemical cycle, $\text{XCl}_2(s)$ dissolves according to: $\text{XCl}_2(s) \rightarrow \text{X}^{2+}(aq) + 2\text{Cl}^-(aq)$ with $\Delta H_{\text{solution}} = +15 \text{ kJ mol}^{-1}$. If the hydration enthalpy of $\text{X}^{2+}$ is $-2176 \text{ kJ mol}^{-1}$ and of $\text{Cl}^-$ is $-364 \text{ kJ mol}^{-1}$, and the Born-Landé equation predicts a lattice energy of $2850 \text{ kJ mol}^{-1}$, what can be concluded about the ionic character of $\text{XCl}_2$?

Consider the following energy cycle for the formation of $\text{Al}_2\text{O}_3$: Step 1: $2\text{Al}(s) \rightarrow 2\text{Al}(g)$ $\Delta H = +652 \text{ kJ}$; Step 2: $\frac{3}{2}\text{O}_2(g) \rightarrow 3\text{O}(g)$ $\Delta H = +747 \text{ kJ}$; Step 3: $2\text{Al}(g) \rightarrow 2\text{Al}^{3+}(g) + 6e^-$ $\Delta H = +11340 \text{ kJ}$; Step 4: $3\text{O}(g) + 6e^- \rightarrow 3\text{O}^{2-}(g)$ $\Delta H = +2196 \text{ kJ}$. If $\Delta H_f[\text{Al}_2\text{O}_3] = -1676 \text{ kJ mol}^{-1}$, why is Step 4 endothermic despite oxygen gaining electrons?

Which statement provides the fundamental reason why Hess's Law is a valid method for calculating enthalpy changes?

Which compound is expected to have the lattice enthalpy with the largest magnitude?

In the Born-Haber cycle for the formation of solid magnesium chloride (MgCl₂), which process corresponds to the second ionization energy of magnesium?

Consider the Born-Haber cycles for the formation of sodium fluoride (NaF) and magnesium oxide (MgO). Which statement correctly compares the energy terms involved?

The magnitude of the lattice enthalpy for the alkali metal chlorides, MCl, decreases progressively from LiCl to CsCl. What is the primary reason for this trend?