NUMS — Medical & Dental Entry Test
Take the NUMS Chemistry — Inorganic and Organic Chemistry (Set 6): 30 multiple-choice questions (40 minutes) with instant scoring and a full answer…
What this test covers
The first 5 questions of this test, with the correct answer and explanation.
Q1. Temporary hardness in a water supply is due to dissolved calcium hydrogencarbonate. A household kettle boils 10.0 dm³ of water containing 162 mg dm⁻³ of Ca(HCO₃)₂ (M = 162 g mol⁻¹), decomposing it completely to CaCO₃, CO₂ and H₂O. What mass of CaCO₃ (M = 100 g mol⁻¹) is deposited as scale?
Answer: D. 1.00 g
Explanation: Ca(HCO₃)₂ = 10.0 × 0.162 g = 1.62 g = 0.0100 mol. Ca(HCO₃)₂ → CaCO₃ + CO₂ + H₂O gives 1 mol CaCO₃ per mol, so mass = 0.0100 × 100 = 1.00 g.
Q2. Xenon hexafluoride reacts completely with water: XeF₆ + 3H₂O → XeO₃ + 6HF. How many moles of hydrogen fluoride are formed from 0.25 mol of XeF₆?
Answer: D. 1.5 mol
Explanation: The equation shows 6 mol HF per mol XeF₆, so 0.25 mol XeF₆ gives 0.25 × 6 = 1.5 mol HF. The other product, XeO₃, is an explosive solid.
Q3. Bleaching powder, CaOCl₂ (Ca = 40, O = 16, Cl = 35.5), releases chlorine when treated with dilute acid: CaOCl₂ + H₂SO₄ → CaSO₄ + H₂O + Cl₂. What is the maximum percentage of available chlorine (as Cl₂) by mass in pure CaOCl₂?
Answer: B. 55.9%
Explanation: One mole of CaOCl₂ (127 g) releases one mole of Cl₂ (71 g). Available chlorine = 71/127 × 100 = 55.9%.
Q4. Which of these oxides is neutral, showing neither acidic nor basic properties?
Answer: B. N₂O
Explanation: N₂O (like CO and NO) does not react with water, acids or alkalis. N₂O₅ is acidic (forms HNO₃), CaO is basic, and Al₂O₃ is amphoteric.
Q5. Phosphorus(V) oxide is completely hydrolysed by excess water. How many moles of H₃PO₄ are obtained from 1 mol of P₄O₁₀?
Answer: C. 4
Explanation: P₄O₁₀ + 6H₂O → 4H₃PO₄. Each P atom ends up in one H₃PO₄ molecule, and P₄O₁₀ contains four P atoms, so 4 mol of H₃PO₄ form.
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Q6. A single-chain silicate has the repeating unit (SiO₃)ₙ²ⁿ⁻, built from SiO₄ tetrahedra. How many oxygen atoms of each tetrahedron are shared with neighbouring tetrahedra?
Q7. How are the 12 valence electrons of diborane, B₂H₆, distributed among its bonds?
Q8. A yellow solution of potassium chromate turns orange when dilute sulphuric acid is added. Which change explains this?
Q9. How many unpaired electrons are present in the Fe³⁺ ion (atomic number of Fe = 26) in its ground state?
Q10. The anticancer drug [Pt(NH₃)₂Cl₂] exists as two different compounds, cis and trans. What does this tell us about the geometry of the complex?
Q11. Limestone is added to the charge in a blast furnace. What is the main role of the limestone?
Q12. What is the IUPAC name of CH₃–CH=CH–CH(OH)–CH₃ (ignoring E/Z isomerism)?
Q13. How many structural isomers (ignoring stereoisomers) have the molecular formula C₃H₆Cl₂?
Q14. 2,3-Dihydroxybutanedioic acid (tartaric acid), HOOC–CH(OH)–CH(OH)–COOH, has two chiral centres. How many stereoisomers does it have in total?
Q15. Which of these carbocations is the most stable?
Q16. Propene is treated first with diborane (B₂H₆) in ether and then with alkaline hydrogen peroxide. What is the main product?
Q17. Propyne is warmed with dilute sulphuric acid and mercury(II) sulphate. What is the final product?
Q18. Chlorobenzene undergoes nitration more slowly than benzene, yet the products are mainly 2- and 4-nitrochlorobenzene. What explains this?
Q19. Which pair of reactants is best for preparing tert-butyl methyl ether, (CH₃)₃C–O–CH₃, by the Williamson synthesis?
Q20. Benzaldehyde is warmed with concentrated sodium hydroxide solution. What are the products?
Q21. Propanone is heated with zinc amalgam and concentrated hydrochloric acid. What is the product?
Q22. Which of these liberates carbon dioxide when added to aqueous sodium hydrogencarbonate?
Q23. Ethanamide is treated with bromine and aqueous sodium hydroxide (Hofmann bromamide reaction). Which amine is formed?
Q24. Aniline is diazotised with NaNO₂ and HCl, and the temperature is kept at 0–5 °C. Why is the temperature not allowed to rise much higher?
Q25. Glycine has pKₐ values of 2.34 (–COOH) and 9.60 (–NH₃⁺). What is its isoelectric point, taking pI as the mean of the two pKₐ values?
Q26. A protein is made of 120 amino acid residues arranged in two separate polypeptide chains. How many peptide bonds does it contain?
Q27. Lactose, the sugar in milk, is hydrolysed by the enzyme lactase. What are the products?
Q28. Tristearin (M = 890 g mol⁻¹) is completely saponified by hot excess NaOH to give glycerol (M = 92 g mol⁻¹) and sodium stearate. What mass of glycerol is obtained from 8.9 g of tristearin?
Q29. Nylon-6 is made from caprolactam; its repeating unit –NH(CH₂)₅CO– has a molar mass of 113 g mol⁻¹. A polymer sample has an average molar mass of 22 600 g mol⁻¹. What is the average degree of polymerisation?
Q30. A few drops of freshly prepared iron(II) sulphate solution are added to a solution, and concentrated sulphuric acid is carefully run down the side of the test tube. A brown ring forms where the liquids meet. Which ion is detected?