Explain how UV light or heat breaks a halogen molecule homolytically so that each atom keeps one electron, write the initiation equation with fish-hook arrows showing single-electron movement, and contrast homolytic with heterolytic fission.
Tę umiejętność sprawdza 15 zadań wzorowanych na arkuszach IB z lat 2022–2026.
Pentane reacts with bromine, Br2, to form 2-bromopentane. (i) Explain, using equations, the initiation step and two propagation steps for this reaction. (ii) 2-Bromopentane reacts with aqueous sodium hydroxide, NaOH(aq), to form pentan-2-ol,…
Methane reacts with bromine gas in the presence of UV radiation to produce brominated hydrocarbons. (i) Explain, using an equation, how a bromine molecule undergoes homolytic fission. (ii) Using two equations, explain the propagation steps in the substitution…
Ethane, C2H6, reacts with chlorine, Cl2, to produce chloroethane, C2H5Cl. (i) Outline why the reaction does not start unless the mixture is exposed to ultraviolet light. (ii) Deduce two propagation steps and one termination step for this…
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…
The rate of the reaction between compound Y and aqueous sodium hydroxide depends on the concentrations of both reactants. (i) Explain the mechanism of this reaction, using curly arrows to show the movement of electron pairs. (ii) Explain why…
(i) Concentrated sulfuric acid, H2SO4, is used as the catalyst in the manufacture of propyl ethanoate. Explain how the catalyst affects the reaction. (ii) The conversion of propane into 1-bromopropane,…
Chlorinated solvents such as tetrachloromethane, CCl4, and 1,1,1-trichloroethane, CH3CCl3, were once common in laboratories, but their production is now restricted by an international agreement. Besides climate change, state the specific…
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
(i) Iodine molecules, I2, undergo homolytic fission when they absorb light. Write an equation for this process, using curly arrows to show the movement of the electrons. (ii) In the presence of a suitable reagent the I–I bond can instead break…
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.
Ethane reacts with bromine gas, Br2(g), in the presence of UV light to form bromoethane. State the type of this reaction and the name of its mechanism.
Bromine radicals form when the bond in a bromine molecule is broken by ultraviolet light. The energy needed to break the bond in one molecule of Br2 is 3.21 × 10−19 J. (i) Calculate the minimum frequency of light needed to break this…
Ozone, O3, absorbs ultraviolet radiation with a wavelength of 300 nm and dissociates. Oxygen, O2, does not dissociate at this wavelength. Which comparison of the bonds in O3 with the bond in O2 is correct? A. Longer and weaker B.…
Which reaction involves homolytic fission of a bond? A. C2H6 + Br2 in the presence of UV light B. CH3CH2Br + NaOH(aq) warmed C. CH2=CH2 + HBr at room temperature D. C6H6 + Br2 with FeBr3 as catalyst
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