Halogenoalkanes Practice Questions PDF

1. What is the general formula of a halogenoalkane? * A) CnH2n+2X * B) CnH2n+1X * C) CnH2nX * D) CnHnX2 2. Which of the following is the most polar bond? * A) C-F * B) C-Cl * C) C-Br * D) C-I 3. Which of the following is generally the *least* polar bond? * A) C-F * B) C-Cl * C) C-Br * D) C-I 4. W...

1. What is the general formula of a halogenoalkane? * A) CnH2n+2X * B) CnH2n+1X * C) CnH2nX * D) CnHnX2 2. Which of the following is the most polar bond? * A) C-F * B) C-Cl * C) C-Br * D) C-I 3. Which of the following is generally the *least* polar bond? * A) C-F * B) C-Cl * C) C-Br * D) C-I 4. What type of species is attracted to the carbon atom in the C-X bond of a halogenoalkane? * A) Electrophiles * B) Nucleophiles * C) Free radicals * D) Oxidising agents 5. What is the most common type of reaction that halogenoalkanes undergo? * A) Electrophilic addition * B) Nucleophilic substitution * C) Electrophilic substitution * D) Free radical addition 6. Which of the following is a nucleophile? * A) H+ * B) NH3 * C) Br2 * D) HBr 7. In a nucleophilic substitution reaction of a halogenoalkane, what is the leaving group? * A) The nucleophile * B) The halogen atom * C) The carbon atom * D) A hydrogen atom 8. What is the product of the reaction between bromoethane and aqueous sodium hydroxide? * A) Ethane * B) Ethene * C) Ethanol * D) Sodium bromide 9. What is the product when a halogenoalkane reacts with ammonia? * A) An alcohol * B) An amine * C) An alkene * D) A nitrile 10. What is the product when a halogenoalkane reacts with cyanide ions (CN-)? * A) An alcohol * B) An amine * C) An alkene * D) A nitrile 11. What conditions favor *elimination* reactions in halogenoalkanes over substitution? * A) Cold, dilute aqueous alkali * B) Hot, concentrated alcoholic alkali * C) Hot, concentrated aqueous alkali * D) Cold, dilute alcoholic alkali 12. What is the product of an elimination reaction with a halogenoalkane? * A) An alcohol * B) An amine * C) An alkene * D) A nitrile 13. What is formed when 1-chloropropane undergoes an elimination reaction? * A) propan-1-ol * B) propan-2-ol * C) propane * D) Propene 14. How does the C-X bond enthalpy change down the halogen group (from F to I)? * A) Increases * B) Decreases * C) Stays the same * D) Fluctuates randomly 15. How does the rate of nucleophilic substitution generally change down the halogen group (from F to I in C-X)? * A) Decreases * B) Increases * C) Stays the same * D) Depends on the nucleophile 16. Which factor is more important in determining the rate of nucleophilic substitution in halogenoalkanes? * A) C-X bond polarity * B) C-X bond enthalpy * C) Nucleophile concentration * D) Temperature 17. What type of reaction mechanism is typically involved when a *primary* halogenoalkane reacts with hydroxide ions? * A) SN1 * B) SN2 * C) E1 * D) E2 18. In an SN2 reaction, how many steps are in the mechanism? * A) 1 * B) 2 * C) 3 * D) 4  19. What is a signi cant use of halogenoalkanes? * A) fuels * B) refrigerants * C) fertilisers * D) food colouring 20. What environmental problem is associated with CFCs (chloro uorocarbons)? * A) Acid rain * B) Ozone depletion * C) Global warming (directly) * D) Smog formation Answers and Explanations: 1. B) CnH2n+1X - This is the general formula for a halogenoalkane. 2. A) C-F - Fluorine is the most electronegative halogen. 3. D) C-I - Iodine is the least electronegative halogen. 4. B) Nucleophiles - The carbon atom in the C-X bond is partially positive. 5. B) Nucleophilic substitution - This is the characteristic reaction. 6. B) NH3 - Ammonia has a lone pair of electrons. 7. B) The halogen atom - The halogen leaves as a halide ion. 8. C) Ethanol - Hydroxide acts as a nucleophile, substituting the Br. 9. B) An amine - Ammonia acts as a nucleophile. 10. D) A nitrile - Cyanide acts as a nucleophile, extending the carbon chain. 11. B) Hot, concentrated alcoholic alkali - These conditions favour elimination. fl fi 12. C) An alkene - Elimination reactions remove HX, forming a C=C bond. 13. D) Propene - Elimination of HCl forms the C=C double bond. 14. B) Decreases - Bond strength decreases down the group. 15. B) Increases - Weaker C-X bonds break more easily. 16. B) C-X bond enthalpy - Bond strength is more important than polarity. 17. B) SN2 - SN2 is favored for primary halogenoalkanes. 18. A) 1 a concerted, single step reaction 19. B) refrigerants Correct de nition. 20. B) Ozone depletion - CFCs release chlorine radicals, which catalyse ozone destruction. fi