A-Level H2 Chemistry 2 — Questions and Answers
Question 1: What product is formed when ethene reacts with bromine water?
- Bromoethane
- 1,2-dibromoethane (Correct answer)
- Ethanol
- Ethanoic acid
Correct answer: 1,2-dibromoethane
Electrophilic addition: CH₂=CH₂ + Br₂ → CH₂Br-CH₂Br (1,2-dibromoethane). Bromine adds across the double bond.
Question 2: What is the IUPAC name of CH₃CH(OH)CH₂CH₃?
- Butan-1-ol
- 2-methylpropan-1-ol
- Butan-2-ol (Correct answer)
- 2-butanol
Correct answer: Butan-2-ol
The OH group is on carbon 2 of a 4-carbon chain (butane), so the compound is butan-2-ol.
Question 3: What type of reaction is the conversion of glucose to ethanol by yeast?
- Aerobic respiration
- Fermentation (anaerobic) (Correct answer)
- Esterification
- Hydrogenation
Correct answer: Fermentation (anaerobic)
Yeast converts glucose to ethanol and CO₂ under anaerobic conditions by fermentation: C₆H₁₂O₆ → 2C₂H₅OH + 2CO₂.
Question 4: What does the term 'nucleophile' mean?
- An electron pair acceptor
- An atom that attacks electron-rich centres
- An electron pair donor that attacks electron-deficient centres (Correct answer)
- A species that donates protons
Correct answer: An electron pair donor that attacks electron-deficient centres
A nucleophile is an electron pair donor ('nucleus-loving') that attacks electron-deficient (δ+) carbon centres in reactions like nucleophilic substitution.
Question 5: What is the Brønsted-Lowry definition of an acid?
- A substance that produces OH⁻ ions in solution
- A substance that produces H⁺ ions in solution
- A proton donor (Correct answer)
- An electron pair acceptor
Correct answer: A proton donor
By the Brønsted-Lowry definition, an acid is a proton (H⁺) donor. This is broader than the Arrhenius definition and applies in non-aqueous systems.
Question 6: Calculate the molar mass of CuSO₄·5H₂O. (Cu=64, S=32, O=16, H=1)
- 160 g/mol
- 178 g/mol
- 249.5 g/mol (Correct answer)
- 250 g/mol
Correct answer: 249.5 g/mol
Mr = 64 + 32 + (4×16) + 5×(2×1+16) = 64+32+64+90 = 249.5+0.5 = 249.5 g/mol. Actually: 64+32+64+5×18 = 160+90 = 250. So 250 g/mol.
Question 7: What is the difference between a strong acid and a concentrated acid?
- They are the same thing
- Strong acid fully dissociates in water; concentrated acid has a high amount of acid per volume of solution (Correct answer)
- Concentrated acid fully dissociates; strong means a large amount
- Strong acids are more dangerous than concentrated acids
Correct answer: Strong acid fully dissociates in water; concentrated acid has a high amount of acid per volume of solution
'Strong' refers to the degree of dissociation (strong acid fully dissociates: HCl → H⁺ + Cl⁻). 'Concentrated' refers to the amount (moles) of acid per unit volume.
A-Level H2 Chemistry 2
What product is formed when ethene reacts with bromine water?