R3.3 Electron sharing reactions
15 revision questions with answers for R3.3 Electron sharing reactions, marked SL. Read them here, or play the set as a class game on the projector. Free to host, and students join with a code.
Species with an unpaired electron?
- Cation
- Anion
- RadicalRight answer
- Nucleophile
What this set covers
Free-radical chemistry: radicals, homolytic fission, the chlorination of methane in UV light with initiation, propagation and termination steps, further substitution products, and the bromine test on alkanes.
- Common mix-up
- Students often mix up propagation and termination: propagation uses a radical and makes a new one, while termination combines two radicals, as in two methyl radicals forming ethane.
- Revision tip
- Write out all three stages for methane and chlorine from memory with the dot on every radical, then check that propagation steps regenerate Cl•.
All 15 questions and answers
Species with an unpaired electron?
Answer: Radical
Bond breaking in which each atom keeps one of the shared electrons?
Answer: Homolytic fission
Condition needed to split Cl₂ into chlorine atoms when it reacts with methane?
Answer: UV light
UV splits Cl–Cl rather than C–H because the Cl–Cl bond has a…?
Answer: Lower bond enthalpy
Equation for the initiation step in the chlorination of methane?
Answer: Cl₂ → 2Cl•
Step in which a radical reacts and a new radical forms?
Answer: Propagation
Step in which two radicals combine?
Answer: Termination
Products of the propagation step CH₄ + Cl•?
Answer: CH₃• + HCl
Products of the propagation step CH₃• + Cl₂?
Answer: CH₃Cl + Cl•
Product when two methyl radicals combine?
Answer: Ethane
Type of reaction between methane and chlorine in UV light?
Answer: Substitution
Dichloromethane forms alongside chloromethane because of…?
Answer: Further substitution
Alkanes are fairly unreactive because their C–C and C–H bonds are strong and of…?
Answer: Low polarity
Symbol used to show the unpaired electron of a radical?
Answer: A dot
Colour change when bromine reacts with hexane in UV light?
Answer: Orange to colourless
Play it as a class game
Play this set opens it in splycr, where you can host it for your class straight away. Hosting needs no account: put the room code on the projector, and students join from a phone with the code and their first name. Each question plays as multiple choice, and the three wrong options were written for that question.