NUMS — Medical & Dental Entry Test

NUMS Chemistry — Fundamental Concepts, Atomic Structure and Bonding (Set 1)

Take the NUMS Chemistry — Fundamental Concepts, Atomic Structure and Bonding (Set 1): 30 multiple-choice questions (40 minutes) with instant scoring and a…

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. A hospital IV bag holds 500 mL of 5% (w/v) glucose solution (C₆H₁₂O₆, M = 180 g mol⁻¹). How many moles of glucose does the bag deliver to the patient?
- A. 1.39 mol
- B. 0.069 mol
- C. 0.139 mol ✓
- D. 0.278 mol
Answer: C. 0.139 mol
Explanation: 5% w/v means 5 g per 100 mL, so 500 mL holds 25 g. Moles = 25/180 = 0.139 mol.
Q2. Normal saline used in drips contains 9.0 g of NaCl per litre. What is the amount of sodium ions in one litre of normal saline? (NaCl = 58.5 g mol⁻¹)
- A. 0.308 mol
- B. 0.077 mol
- C. 0.154 mol ✓
- D. 1.54 mol
Answer: C. 0.154 mol
Explanation: Moles NaCl = 9.0/58.5 = 0.154 mol; each formula unit gives one Na⁺, so Na⁺ = 0.154 mol.
Q3. A tablet of the antacid magnesium hydroxide contains 5.8 g of Mg(OH)₂ (M = 58 g mol⁻¹). According to Mg(OH)₂ + 2HCl → MgCl₂ + 2H₂O, how many moles of stomach HCl can it neutralise?
- A. 0.4 mol
- B. 0.2 mol ✓
- C. 0.1 mol
- D. 0.05 mol
Answer: B. 0.2 mol
Explanation: 5.8/58 = 0.1 mol Mg(OH)₂; the 1 : 2 mole ratio gives 0.2 mol HCl.
Q4. In a lab preparation of aspirin, 13.8 g of salicylic acid (M = 138) is converted 1 : 1 into aspirin (M = 180). If 14.4 g of aspirin is obtained, what is the percentage yield?
- A. 78%
- B. 72%
- C. 104%
- D. 80% ✓
Answer: D. 80%
Explanation: Theoretical yield = 0.1 mol × 180 = 18.0 g. % yield = 14.4/18.0 × 100 = 80%.
Q5. Urea, CO(NH₂)₂, is the main nitrogenous waste in human urine. What is the percentage by mass of nitrogen in urea? (C = 12, O = 16, N = 14, H = 1)
- A. 46.7% ✓
- B. 60.0%
- C. 31.8%
- D. 23.3%
Answer: A. 46.7%
Explanation: M(urea) = 60 g mol⁻¹ and it contains 2 N = 28 g. %N = 28/60 × 100 = 46.7%.

The other 25 questions

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Q6. Ozone (O₃) in the stratosphere filters UV radiation. How many oxygen atoms are present in 0.5 mol of ozone? (Nₐ = 6.02 × 10²³ mol⁻¹)
- A. 6.02 × 10²³
- B. 9.03 × 10²³
- C. 3.01 × 10²³
- D. 1.81 × 10²⁴
Q7. Cobalt-60 (atomic number 27) is used as a gamma source in cancer radiotherapy. How many neutrons does one ⁶⁰Co nucleus contain?
- A. 27
- B. 60
- C. 33
- D. 87
Q8. Iodine-131 is used to treat an overactive thyroid while natural iodine is iodine-127. Which statement about these two isotopes is correct?
- A. They have the same mass but different numbers of electrons
- B. They have the same chemical properties but ¹³¹I has four more neutrons
- C. They have different chemical properties because their proton numbers differ
- D. ¹³¹I has four more protons and the same number of neutrons
Q9. Which of the following sets of quantum numbers (n, l, m) is NOT allowed for an electron?
- A. n = 2, l = 1, m = +1
- B. n = 2, l = 2, m = 0
- C. n = 3, l = 2, m = −2
- D. n = 4, l = 0, m = 0
Q10. Iron in haemoglobin is present as Fe²⁺ (Fe, Z = 26). What is the electronic configuration of Fe²⁺?
- A. [Ar] 3d⁶ 4s²
- B. [Ar] 3d⁴ 4s²
- C. [Ar] 3d⁵ 4s¹
- D. [Ar] 3d⁶
Q11. Copper (Z = 29) is a cofactor in the enzyme cytochrome oxidase, where it cycles as Cu²⁺. How many unpaired electrons does a Cu²⁺ ion have?
- A. 0
- B. 2
- C. 1
- D. 3
Q12. Using the Bohr model, the energy of the electron in a hydrogen atom is Eₙ = −13.6/n² eV. What is the energy of the electron in the second orbit?
- A. −27.2 eV
- B. −6.8 eV
- C. −3.4 eV
- D. −1.51 eV
Q13. The lines of the hydrogen spectrum that lie in the visible region belong to which series, and to which lower level do the electrons fall?
- A. Balmer series, falling to n = 2
- B. Paschen series, falling to n = 3
- C. Lyman series, falling to n = 1
- D. Balmer series, falling to n = 1
Q14. A hydrogen discharge tube emits light as electrons drop between Bohr levels. Of the four drops listed, which one gives out the most energetic photon?
- A. n = 3 → n = 2
- B. n = 4 → n = 3
- C. n = 2 → n = 1
- D. n = 4 → n = 2
Q15. An electron and a proton are moving with the same speed. Which statement about their de Broglie wavelengths is correct?
- A. The electron has the longer wavelength because its momentum is smaller
- B. The proton has the longer wavelength because it is heavier
- C. Only the electron has a wavelength because the proton is a particle
- D. Both have equal wavelengths because their speeds are equal
Q16. How many radial nodes are present in a 3s orbital?
- A. 1
- B. 3
- C. 2
- D. 0
Q17. Nitrogen (Z = 7) is an essential element of all amino acids. According to Hund's rule, how many unpaired electrons does a nitrogen atom have in its ground state?
- A. 1
- B. 3
- C. 5
- D. 2
Q18. The first ionisation energy of oxygen is lower than that of nitrogen even though oxygen has a higher nuclear charge. What is the best explanation?
- A. Nitrogen has a completely filled 2p subshell
- B. Oxygen's paired 2p electrons repel each other, making one easier to remove
- C. Oxygen's 2p electrons are better shielded by its 2s electrons
- D. Oxygen has a larger atomic radius than nitrogen
Q19. Ammonia formed during protein breakdown is converted to urea in the liver. What are the shape and approximate bond angle of an NH₃ molecule?
- A. Trigonal pyramidal, about 107°
- B. Tetrahedral, 109.5°
- C. Bent, about 104.5°
- D. Trigonal planar, 120°
Q20. Carbon dioxide is exhaled from the lungs. What is the hybridisation of the carbon atom in CO₂?
- A. dsp²
- B. sp
- C. sp³
- D. sp²
Q21. Water (M = 18) boils at 100 °C while hydrogen sulphide (M = 34) boils at about −60 °C. What mainly accounts for this difference?
- A. Stronger London forces in water
- B. The larger molecular mass of water
- C. Hydrogen bonding between water molecules
- D. Ionic bonding in water
Q22. Each C–Cl bond in carbon tetrachloride is polar, yet the CCl₄ molecule has zero dipole moment. Why?
- A. The four bond dipoles cancel in its symmetrical tetrahedral shape
- B. The C–Cl bonds are ionic, not covalent
- C. Carbon and chlorine have equal electronegativities
- D. CCl₄ contains a lone pair on carbon
Q23. Ethyne (acetylene), C₂H₂, is used in oxy-acetylene welding. How many sigma (σ) and pi (π) bonds does one molecule contain?
- A. 2 σ and 3 π
- B. 5 σ and 0 π
- C. 3 σ and 2 π
- D. 3 σ and 1 π
Q24. According to molecular orbital theory, oxygen gas (O₂) is attracted into a magnetic field. Which statement explains this?
- A. O₂ has bond order 3 and no unpaired electrons
- B. O₂ has bond order 1 and one unpaired electron
- C. O₂ has bond order 2 and all electrons paired
- D. O₂ has bond order 2 and two unpaired electrons in π* orbitals
Q25. Which of the following oxygen species has the highest bond order?
- A. O₂⁺
- B. O₂²⁻
- C. O₂⁻
- D. O₂
Q26. Which compound has the greatest ionic character in its bonding?
- A. MgCl₂
- B. LiI
- C. KF
- D. NaBr
Q27. Natural chlorine is 75% ³⁵Cl and 25% ³⁷Cl, as shown by its mass spectrum. What is the relative atomic mass of chlorine?
- A. 35.5
- B. 35.0
- C. 36.0
- D. 36.5
Q28. The water molecule has a bond angle of about 104.5°, smaller than the tetrahedral angle of 109.5°. What causes this?
- A. Two lone pairs on oxygen repel the bond pairs more strongly
- B. The large size of the hydrogen atoms
- C. sp² hybridisation of the oxygen atom
- D. Hydrogen bonding between neighbouring molecules
Q29. 4.0 g of sodium hydroxide (M = 40 g mol⁻¹) is dissolved in water and the solution is made up to 250 cm³. What is its molarity?
- A. 0.1 mol dm⁻³
- B. 1.6 mol dm⁻³
- C. 0.016 mol dm⁻³
- D. 0.4 mol dm⁻³
Q30. During cellular respiration glucose is oxidised: C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O. What volume of CO₂, measured at STP, is produced when 0.1 mol of glucose is completely oxidised?
- A. 2.24 dm³
- B. 22.4 dm³
- C. 13.44 dm³
- D. 6.72 dm³