Explain that breaking bonds absorbs energy and forming bonds releases it, and calculate the enthalpy change of a gas-phase reaction as bonds broken minus bonds formed using average bond enthalpy data from the data booklet.
Tę umiejętność sprawdzają 22 zadania wzorowane na arkuszach IB z lat 2022–2026.
(i) Determine the enthalpy of combustion of pentane, in kJ mol−1, using table 12 in the data booklet. C5H12(g) + 8 O2(g) → 5 CO2(g) + 6 H2O(g) (ii) Calculate the mass, in g, of carbon dioxide, CO2, produced when 45.0 g of pentane react with…
Propane undergoes complete combustion. C3H8(g) + 5 O2(g) → 3 CO2(g) + 4 H2O(g) (i) Calculate the enthalpy change of reaction, ΔH, in kJ mol−1, for the combustion of propane. Use section 12 of the data booklet. (ii) State the…
Use bond enthalpies to calculate the enthalpy change, in kJ mol−1, for the first reaction. Br ∙ (g) + O3(g) → BrO ∙ (g) + O2(g) Use section 12 of the data booklet and the table below.
The enthalpy change for the combustion of propane is calculated from bond enthalpy data and compared with the literature value. C3H8(g) + 5 O2(g) → 3 CO2(g) + 4 H2O(l) Which statement best explains why the calculated value is less negative than the…
Suppose carbonyl dibromide were made by a free-radical chain reaction of carbon monoxide, CO, with bromine vapour, Br2, started by ultraviolet light. The questions below treat this hypothetical route with the bond-enthalpy model. (i) Write an…
Propene reacts with bromine to produce 1,2-dibromopropane. CH3CH=CH2(g) + Br2(g) → CH3CHBrCH2Br(g) Calculate the enthalpy, in kJ, of the reaction using section 12 of the data booklet.
(i) Calculate the enthalpy change, ΔH, for the overall synthesis of propyl ethanoate from propane and ethane shown above. Use section 12 of the data booklet. (ii) Two students each calculated the enthalpy change for the reaction between propan-1-ol and…
Determine the standard enthalpy change of the reaction, in kJ mol⁻¹. Use section 12 of the data booklet. Ignore interactions between ions and the solvent.
What is ΔH, in kJ, in the energy cycle below? A. +20 - 165 B. +20 + 165 C. -20 + 165 D. -20 - 165
Which reaction has the lowest activation energy? A. HBr(g) → H(g) + Br(g) B. 2 Cl(g) → Cl2(g) C. CH4(g) + Cl(g) → CH3(g) + HCl(g) D. HBr(g) → H+(g) + Br−(g)
Which radical is most likely to form when one covalent bond in bromochlorodifluoromethane, CBrClF2, is broken by ultraviolet light in the upper atmosphere? A. •CBrF2 B. •CClF2 C. •CBrClF D. •CBrClF2
In an oil refinery, nonadecane can be cracked into smaller molecules. Consider the reaction: C19H40(g) → 3 C3H6(g) + C10H22(g) Determine the standard enthalpy change, ΔH⊖, for this reaction using section 12 of the data booklet.
For which reactions can the enthalpy change be calculated using only average bond enthalpy data? I. N2(g) + O2(g) → 2 NO(g) II. C2H4(g) + H2(g) → C2H6(g) III. 2 H2O2(l) → 2 H2O(l) + O2(g) A. I and II only B. I and III only C. II and III…
The enthalpy change of the reaction below is calculated from average bond enthalpies. H2(g) + Cl2(g) → 2 HCl(g) Average bond enthalpies: H−H 436 kJ mol−1, Cl−Cl 242 kJ mol−1, H−Cl…
Which statement about the energy changes in a reaction between covalent molecules is correct? A. The enthalpy change of the reaction equals the sum of the bond enthalpies of the bonds broken minus the sum of the bond enthalpies of the bonds formed B. The…
(i) Write the equation for the complete combustion of propan-1-ol, CH3CH2CH2OH. (ii) Determine the enthalpy change, in kJ mol−1, for the combustion of gaseous propan-1-ol to give gaseous carbon dioxide and gaseous water, using bond…
Hydrogen atoms in the gas phase combine to form a covalent bond: H(g) + H(g) → H2(g) Which statement describes the energy change? A. Energy is absorbed and ΔH is positive B. Energy is released and ΔH is positive C. Energy is released…
Approximate enthalpy changes of reactions can be found from bond enthalpies. (i) Determine the enthalpy change, ΔH⊖, of this reaction, in kJ mol−1, using section 12 of the data booklet. (ii) Each bond enthalpy is uncertain by 0.1…
Bond enthalpies give an estimate of the enthalpy change of a reaction. Assume that all species are gases. (i) Use bond enthalpies from section 12 of the data booklet to determine the standard enthalpy change, ΔH⊖, of the forward reaction. (ii)…
Whether a higher temperature favours the formation of methanol depends on the enthalpy change of the reaction CO(g) + 2 H2(g) → CH3OH(g) (i) Determine the enthalpy change, ΔH, for the production of methanol, in kJ, using bond enthalpies. Use…
Ethane reacts with iodine vapour. C2H6(g) + I2(g) → C2H5I(g) + HI(g) (i) Calculate the enthalpy change of the reaction, ΔH, using section 12 of the data booklet. (ii) Draw and label an enthalpy level diagram for this reaction on the axes below.
Which change is exothermic? A. Cl2(g) → 2 Cl(g) B. H2O(l) → H2O(g) C. CH4(g) → C(g) + 4 H(g) D. H(g) + Br(g) → HBr(g)
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