Enthalpy change from bond enthalpies

Suppose carbonyl dibromide were made by a free-radical chain reaction of carbon monoxide, $\ce{CO}$, with bromine vapour, $\ce{Br2}$, 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. $\ce{C4H8(g) + H2(g) -> C4H10(g)}$ (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 $\mathrm{kJ\,mol^{-1}}$ for the combustion of…

(i) Calculate the enthalpy change, $\Delta H$, 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 $\mathrm{kJ\,mol^{-1}}$. (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. $\ce{HBr(g) -> H(g) + Br(g)}$ B. $\ce{2Cl(g) -> Cl2(g)}$ C. $\ce{CH4(g) + Cl(g) -> CH3(g) + HCl(g)}$ D. $\ce{HBr(g) -> H+(g) + Br-(g)}$

Which radical is most likely to form when one covalent bond in bromochlorodifluoromethane, $\ce{CBrClF2}$, is broken by ultraviolet light in the upper atmosphere? A. •$\ce{CBrF2}$ B. •$\ce{CClF2}$ C. •$\ce{CBrClF}$ D. •$\ce{CBrClF2}$

Pentadecane can be cracked into smaller molecules. Consider the reaction: $\ce{C15H32(g) -> 3C4H8(g) + C3H8(g)}$ where $\ce{C4H8}$ is but-1-ene. (i) Use the bond enthalpies in section 12 of the data booklet to determine $\Delta H^\ominus$ for this reaction.…

Two observations are made about the halon $\ce{CF2ClBr}$ in the stratosphere. Observation 1 Observation 2 Ultraviolet light breaks $\ce{CF2ClBr}$ down to give bromine radicals rather than chlorine or fluorine radicals. A single bromine radical can destroy many…