NUMS — Medical & Dental Entry Test

NUMS Chemistry — Inorganic and Organic Chemistry (Set 1)

Take the NUMS Chemistry — Inorganic and Organic Chemistry (Set 1): 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. Which trend in atomic radius is observed on moving from sodium to chlorine across period 3?
- A. Radius stays constant because the shell number is the same
- B. Radius decreases because a new shell is added
- C. Radius decreases because nuclear charge increases while shielding stays similar ✓
- D. Radius increases because more electrons are added
Answer: C. Radius decreases because nuclear charge increases while shielding stays similar
Explanation: Across a period electrons enter the same shell while the proton number rises, so the effective nuclear charge increases and pulls electrons closer.
Q2. Tooth enamel is strengthened by fluoride. Fluorine's bonds are highly polar because it has the highest value of which property among all elements?
- A. Ionisation energy
- B. Atomic radius
- C. Electronegativity ✓
- D. Metallic character
Answer: C. Electronegativity
Explanation: Fluorine (4.0 on the Pauling scale) is the most electronegative element because of its small radius and high effective nuclear charge; helium, not fluorine, has the highest ionisation energy.
Q3. Which hydroxide of the Group 2 elements is the most soluble in water?
- A. Ba(OH)₂ ✓
- B. Ca(OH)₂
- C. Be(OH)₂
- D. Mg(OH)₂
Answer: A. Ba(OH)₂
Explanation: Solubility of Group 2 hydroxides increases down the group, so Ba(OH)₂ is most soluble; Mg(OH)₂ (milk of magnesia) is sparingly soluble.
Q4. Lithium resembles magnesium more than other Group 1 metals (e.g. both form nitrides and their carbonates decompose on heating). This is called:
- A. Lanthanide contraction
- B. Inert pair effect
- C. Isoelectronic behaviour
- D. Diagonal relationship ✓
Answer: D. Diagonal relationship
Explanation: Li and Mg have similar charge-to-size ratios (polarising power), producing the diagonal relationship.
Q5. Chlorine water is added to a solution of potassium bromide. What is observed and why?
- A. No change because Br₂ is a stronger oxidant than Cl₂
- B. The solution turns orange because Cl₂ oxidises Br⁻ to Br₂ ✓
- C. A white precipitate of KCl forms
- D. The solution turns violet because I₂ forms
Answer: B. The solution turns orange because Cl₂ oxidises Br⁻ to Br₂
Explanation: Oxidising power falls down Group 17, so Cl₂ + 2Br⁻ → 2Cl⁻ + Br₂, giving an orange-brown colour.

The other 25 questions

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Q6. Most transition metal compounds are coloured, but zinc sulphate solution is colourless. Why?
- A. Zn²⁺ has no d electrons at all
- B. Zinc is not a metal
- C. Zn²⁺ has unpaired electrons that absorb UV only
- D. Zn²⁺ has a completely filled 3d¹⁰ subshell, so no d–d transitions occur
Q7. In the complex ion [Fe(CN)₆]⁴⁻, what are the coordination number and the oxidation state of iron?
- A. 6 and +4
- B. 6 and +2
- C. 6 and +3
- D. 4 and +2
Q8. Nitrogen makes up 78% of air yet is very unreactive at room temperature. Why?
- A. N₂ molecules are ionic
- B. Nitrogen is a noble gas
- C. The N≡N triple bond has a very high bond energy
- D. Nitrogen has no lone pairs
Q9. In the Contact process for manufacturing sulphuric acid, which catalyst is used to oxidise SO₂ to SO₃?
- A. Platinum-rhodium gauze
- B. Iron, Fe
- C. Vanadium(V) oxide, V₂O₅
- D. Nickel, Ni
Q10. Aluminium oxide dissolves both in hydrochloric acid and in sodium hydroxide solution. This shows Al₂O₃ is:
- A. Basic only
- B. Amphoteric
- C. Acidic only
- D. Neutral
Q11. What is the hybridisation of each carbon atom in benzene, C₆H₆?
- A. sp
- B. sp²
- C. sp³d
- D. sp³
Q12. How many structural isomers are possible for pentane, C₅H₁₂?
- A. 5
- B. 2
- C. 3
- D. 4
Q13. When ethanol is warmed with acidified potassium dichromate, the colour changes from orange to green. What happens to the ethanol?
- A. It is reduced to ethane
- B. It is oxidised, first to ethanal and then to ethanoic acid
- C. It is dehydrated to ethene
- D. It is esterified to ethyl ethanoate
Q14. Methane reacts with chlorine in the presence of ultraviolet light. What type of reaction is this?
- A. Electrophilic substitution
- B. Electrophilic addition
- C. Free-radical substitution
- D. Nucleophilic substitution
Q15. What is the major product when HBr adds to propene?
- A. Propan-2-ol
- B. 1-Bromopropane
- C. 2-Bromopropane
- D. 1,2-Dibromopropane
Q16. Which observation shows that a hydrocarbon sample contains a C=C double bond?
- A. It gives a silver mirror with Tollens' reagent
- B. It decolourises bromine water at room temperature
- C. It turns limewater milky
- D. It burns with a blue flame
Q17. Benzene is nitrated with a mixture of concentrated HNO₃ and H₂SO₄. What is the attacking species and the reaction type?
- A. OH⁻; nucleophilic addition
- B. NO₂⁻; nucleophilic substitution
- C. NO₂⁺; electrophilic addition
- D. NO₂⁺; electrophilic substitution
Q18. Which statement about an SN2 reaction of an optically active alkyl halide is correct?
- A. It gives a racemic mixture
- B. Its rate depends only on the alkyl halide
- C. It occurs in one step with inversion of configuration
- D. It occurs in two steps through a carbocation
Q19. Four bromoalkanes are each warmed with aqueous ethanol. Which one undergoes hydrolysis fastest through a carbocation intermediate?
- A. CH₃CH₂–Br
- B. (CH₃)₃C–Br
- C. CH₃CH₂CH₂–Br
- D. CH₃–Br
Q20. In the Lucas test (ZnCl₂ in conc. HCl), which alcohol produces cloudiness immediately?
- A. Methanol
- B. Butan-2-ol
- C. 2-Methylpropan-2-ol
- D. Butan-1-ol
Q21. Phenol is more acidic than ethanol. What is the main reason?
- A. The O–H bond in phenol is shorter
- B. The phenoxide ion is stabilised by delocalisation of its charge into the ring
- C. Ethanol is a stronger electrolyte
- D. Phenol has more hydrogen atoms
Q22. Which compound gives a silver mirror when warmed with Tollens' reagent?
- A. Propanone
- B. Propanal
- C. Propan-2-ol
- D. Propanoic acid
Q23. Which of these compounds gives a yellow precipitate of iodoform (CHI₃) when warmed with iodine and NaOH?
- A. Propanone
- B. Propanal
- C. Methanol
- D. Pentan-3-one
Q24. Ethyl ethanoate, a sweet-smelling compound used in some flavourings, is formed when ethanol is heated with ethanoic acid in the presence of conc. H₂SO₄. This type of reaction is called:
- A. Polymerisation
- B. Esterification
- C. Hydrolysis
- D. Saponification
Q25. The simplest amino acid found in collagen cannot rotate plane-polarised light because it has no chiral carbon. Which amino acid is this?
- A. Glycine
- B. Alanine
- C. Proline
- D. Serine
Q26. Lactic acid, CH₃CH(OH)COOH, builds up in muscles during intense exercise. Why does it exist as two optical isomers?
- A. It forms hydrogen bonds with water
- B. Its central carbon is bonded to four different groups
- C. It has two carboxyl groups
- D. It contains a C=C double bond
Q27. Which linkage joins amino acid units in a protein chain?
- A. –O– (glycosidic bond)
- B. –COO– (ester bond)
- C. –CO–NH– (peptide bond)
- D. –S–S– (disulphide bond)
Q28. Which of the following polymers is formed by condensation polymerisation?
- A. Polythene
- B. Polystyrene
- C. Nylon-6,6
- D. Polyvinyl chloride (PVC)
Q29. Restricted rotation about a C=C bond allows some alkenes to exist as cis and trans forms. Which of these C₄H₈ or C₃H₆ alkenes has such forms?
- A. But-2-ene
- B. 2-Methylpropene
- C. But-1-ene
- D. Propene
Q30. When a fat or oil is boiled with aqueous sodium hydroxide, the products are:
- A. Glycerol and sodium salts of fatty acids (soap)
- B. Ethanol and fatty acids
- C. Amino acids and glycerol
- D. Glucose and glycerol