NUMS — Medical & Dental Entry Test

NUMS Chemistry — Inorganic and Organic Chemistry (Set 3)

Take the NUMS Chemistry — Inorganic and Organic Chemistry (Set 3): 30 multiple-choice questions (40 minutes) with instant scoring and a full answer…

What this test covers

30 NUMS Chemistry

Sample questions with answers

The first 5 questions of this test, with the correct answer and explanation.

Q1. Why is the first ionisation energy of aluminium lower than that of magnesium?
- A. Aluminium atoms are smaller than magnesium atoms
- B. Al loses a 3p electron, which is higher in energy and better shielded than 3s ✓
- C. Aluminium has a larger nuclear charge than magnesium
- D. Aluminium has a completely filled 3s subshell
Answer: B. Al loses a 3p electron, which is higher in energy and better shielded than 3s
Explanation: Mg removes a 3s electron; Al removes a 3p electron, which is further from the nucleus and shielded by the 3s electrons, so less energy is needed.
Q2. Lithium has the most negative standard electrode potential among the alkali metals even though its ionisation energy is the highest. What is the main reason?
- A. The very small Li⁺ ion has a very high hydration energy ✓
- B. Li⁺ has the highest electron affinity
- C. Lithium has the lowest atomic mass
- D. Lithium has the lowest melting point of the group
Answer: A. The very small Li⁺ ion has a very high hydration energy
Explanation: Hydration of the small Li⁺ ion releases so much energy that it outweighs the large ionisation and sublimation energies.
Q3. Which colour is imparted to a Bunsen flame by barium salts?
- A. Golden yellow
- B. Apple green ✓
- C. Brick red
- D. Crimson red
Answer: B. Apple green
Explanation: Barium compounds give an apple-green flame; Sr gives crimson, Na golden yellow and Ca brick red.
Q4. Which of the following sulphates is the least soluble in water?
- A. BaSO₄ ✓
- B. MgSO₄
- C. BeSO₄
- D. CaSO₄
Answer: A. BaSO₄
Explanation: Solubility of Group 2 sulphates decreases down the group because hydration energy falls faster than lattice energy; BaSO₄ is practically insoluble.
Q5. Which of the following carbonates decomposes most easily on heating?
- A. MgCO₃ ✓
- B. BaCO₃
- C. CaCO₃
- D. SrCO₃
Answer: A. MgCO₃
Explanation: Thermal stability of Group 2 carbonates increases down the group as the cation gets larger and polarises the carbonate ion less.

The other 25 questions

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Q6. What is the chemical formula of Plaster of Paris?
- A. CaCO₃·H₂O
- B. CaSO₄·2H₂O
- C. CaSO₄·½H₂O
- D. CaSO₄
Q7. Which of the following reactions will NOT occur?
- A. Br₂ + 2NaI → 2NaBr + I₂
- B. Cl₂ + 2NaI → 2NaCl + I₂
- C. I₂ + 2NaBr → 2NaI + Br₂
- D. Cl₂ + 2NaBr → 2NaCl + Br₂
Q8. Among the hydrogen halides, HI is the strongest acid in aqueous solution. What is the main reason?
- A. The H–I bond is the longest and weakest, so it ionises most readily
- B. Iodine is the most electronegative halogen
- C. HI has the highest polarity
- D. Iodide has the smallest ionic radius
Q9. When sugar (C₁₂H₂₂O₁₁) is treated with concentrated sulphuric acid it turns black. Which property of H₂SO₄ is responsible?
- A. Dehydrating action, removing H and O as water
- B. Catalytic reduction to carbon monoxide
- C. Acidic action producing sulphates
- D. Oxidising action on carbon only
Q10. Nitrogen gas is very unreactive at ordinary temperatures. Which is the main reason?
- A. The N≡N triple bond has a very high bond enthalpy
- B. Nitrogen has a very low electronegativity
- C. The molecule is highly polar
- D. Nitrogen has no valence electrons
Q11. Which of the following oxides is amphoteric?
- A. Al₂O₃
- B. Na₂O
- C. SO₃
- D. MgO
Q12. Why are most transition metal ions coloured while Zn²⁺ is colourless?
- A. Zn²⁺ is unable to form any complexes
- B. Zn²⁺ has no 4s electrons left in it
- C. Partly filled d orbitals allow d–d transitions, but Zn²⁺ has a full 3d¹⁰
- D. Zn²⁺ has an unusually small ionic radius
Q13. What is the oxidation state of iron in potassium hexacyanoferrate(II), K₄[Fe(CN)₆]?
- A. +4
- B. +6
- C. +3
- D. +2
Q14. What is the IUPAC name of the complex [Cu(NH₃)₄]SO₄?
- A. Copper(II) tetraammine sulphate
- B. Tetraamminecopper(II) sulphate
- C. Tetraaminecopper(I) sulphate
- D. Tetraamminecuprate(II) sulphate
Q15. How many structural isomers does pentane (C₅H₁₂) have, including pentane itself?
- A. 4
- B. 2
- C. 3
- D. 5
Q16. What is the IUPAC name of (CH₃)₂CHCH₂CH₂OH?
- A. 3-Methylbutan-4-ol
- B. 2-Methylbutan-4-ol
- C. Isopentanol-3
- D. 3-Methylbutan-1-ol
Q17. 2-Methylpropene reacts with hydrogen bromide. What is the major product?
- A. 1,2-Dibromo-2-methylpropane
- B. 1-Bromo-2-methylpropane
- C. 2-Bromo-2-methylpropane
- D. 2-Methylpropan-2-ol
Q18. Ozonolysis of but-2-ene (CH₃CH=CHCH₃) followed by reductive work-up gives which product?
- A. One molecule of butanal
- B. Two molecules of ethanoic acid only
- C. Two molecules of ethanal
- D. One molecule of butane-2,3-diol
Q19. In the free-radical chlorination of methane, which step is the initiation step?
- A. Cl₂ → 2Cl· under ultraviolet light
- B. 2CH₃· → C₂H₆
- C. CH₄ + Cl· → CH₃· + HCl
- D. CH₃· + Cl₂ → CH₃Cl + Cl·
Q20. In the nitration of benzene, which species is the electrophile?
- A. HNO₃
- B. NO₂⁺
- C. NO₃⁻
- D. NO₂⁻
Q21. What is the role of anhydrous AlCl₃ in the Friedel–Crafts alkylation of benzene with chloromethane?
- A. It acts as a Lewis acid, generating the CH₃⁺ electrophile from CH₃Cl
- B. It oxidises benzene to a radical
- C. It acts as a solvent only
- D. It acts as a Brønsted base removing H⁺ from benzene
Q22. Which organic product is formed when propan-2-ol is heated with acidified potassium dichromate(VI)?
- A. Propene
- B. Propanoic acid
- C. Propanone
- D. Propanal
Q23. Why is phenol a stronger acid than ethanol?
- A. The O–H bond in ethanol is stronger because of hydrogen bonding
- B. Phenol has no hydrogen on oxygen
- C. The phenoxide ion is stabilised by delocalisation of the negative charge into the benzene ring
- D. Phenol has a larger molar mass
Q24. Which of the following will give a silver mirror when warmed with Tollens' reagent?
- A. Propene
- B. Propan-2-ol
- C. Propanal
- D. Propanone
Q25. Ethanoic acid reacts with ethanol in the presence of a little concentrated H₂SO₄ on heating. What is the organic product?
- A. Ethyl ethanoic anhydride
- B. Ethanal
- C. Diethyl ether
- D. Ethyl ethanoate
Q26. What is the name of the reaction in which an ester is heated with aqueous sodium hydroxide to give an alcohol and a sodium carboxylate?
- A. Saponification
- B. Hydrogenation
- C. Esterification
- D. Polymerisation
Q27. In strongly acidic solution (pH ≈ 1), in what form does glycine mainly exist?
- A. H₂N–CH₂–COOH
- B. ⁺H₃N–CH₂–COO⁻
- C. H₂N–CH₂–COO⁻
- D. ⁺H₃N–CH₂–COOH
Q28. Which of the following correctly pairs a polymer with its type of polymerisation?
- A. Nylon-6,6: condensation polymerisation
- B. Nylon-6,6: addition polymerisation
- C. Polyvinyl chloride: condensation polymerisation
- D. Polythene: condensation polymerisation
Q29. Glucose ferments to ethanol: C₆H₁₂O₆ → 2C₂H₅OH + 2CO₂. If the yield is 80%, what mass of ethanol is obtained from 90 g of glucose? (C = 12, H = 1, O = 16)
- A. 36.8 g
- B. 18.4 g
- C. 46.0 g
- D. 73.6 g
Q30. Why does 2-chloro-2-methylpropane hydrolyse faster by the SN1 mechanism than 1-chlorobutane?
- A. Chlorine is a better leaving group in tertiary halides only
- B. The C–Cl bond is shorter
- C. It forms a stable tertiary carbocation intermediate
- D. The molecule is less hindered for backside attack