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 sprawdza 20 zadań wzorowanych 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…
Ethanol can be used as a fuel. (i) Calculate the enthalpy change for the combustion of ethanol using section 12 of the data booklet. C2H5OH(g) + 3 O2(g) → 2 CO2(g) + 3 H2O(g) (ii) The enthalpy of formation of ethanol is defined from its elements. State,…
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.
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 and the entropy…
trans-But-2-ene reacts with hydrogen in the presence of a nickel catalyst to form butane. C4H8(g) + H2(g) → C4H10(g) (i) Calculate, in kJ, the enthalpy change of this reaction from the bond enthalpies in section 12 of the data booklet. (ii) Calculate,…
(i) Outline two advantages of using biobutanol rather than petrol (gasoline) as a fuel for vehicles. (ii) Calculate, using the average bond enthalpies in section 12 of the data booklet, the enthalpy change in kJ mol−1 for the combustion of…
(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…
(i) Using section 12 of the data booklet, determine the standard enthalpy change of the reaction, in kJ mol−1. (ii) A value obtained from bond enthalpies is less accurate than one obtained from enthalpies of formation. State two reasons why.…
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
Pentadecane can be cracked into smaller molecules. Consider the reaction: C15H32(g) → 3 C4H8(g) + C3H8(g) where C4H8 is but-1-ene. (i) Use the bond enthalpies in section 12 of the data booklet to determine ΔH⊖ for this reaction.…
Two observations are made about the halon CF2ClBr in the stratosphere. Which pair of statements explains the observations? Use section 12 of the data booklet. A. The C−Br bond has the highest bond enthalpy of the three carbon–halogen bonds;…
Chlorine molecules, Cl2, and bromine molecules, Br2, can both be split into atoms by radiation. Use section 12 of the data booklet. Explain how the wavelengths of radiation that can split Cl2 and Br2 molecules into atoms compare.
(i) Draw the Lewis (electron dot) structure of carbonyl chloride. (ii) Mark the bond polarities on your Lewis structure using the symbols δ+ and δ−. (iii) Explain the shape of the carbonyl chloride molecule and whether it is polar. (iv) State…
(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…
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)…
The enthalpy change of the reaction is one factor that influences the position of equilibrium. (i) Determine the enthalpy change, ΔH, for the production of methanol, in kJ, using bond enthalpies. Use section 12 of the data booklet. (ii) Outline why a…
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 equation represents the bond enthalpy of the H–Cl bond in hydrogen chloride? A. B. HCl(g) → H+(g) + Cl−(g) C. HCl(g) → H(g) + Cl(g) D. HCl(aq) → H(g) + Cl(g)
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