Esta serie está disponible en su idioma original.
JAMB Chemistry practice questions (CBT)
Fifteen objective questions in the style of the JAMB UTME Chemistry CBT: the mole, atomic structure, bonding, pH, redox, equilibrium, electrolysis, organic chemistry and empirical formulas, each with a worked solution.
Preguntas originales escritas por profesores de Studoli al estilo del examen JAMB UTME. No son exámenes oficiales.
Timed mode
15 questions in 10 minutes, one question at a time. Your answers are marked when you submit or when the time runs out.
Tema: Mole concept
1. How many moles are in 22 g of carbon(IV) oxide, CO₂? (C = 12, O = 16)
Solución
C. 0.5 mol
- Molar mass of CO₂ = 12 + 2 × 16 = 44 g/mol.
- Moles = mass ÷ molar mass = 22 ÷ 44 = 0.5 mol.
Tema: Atomic structure
2. What is the electron configuration of sodium (atomic number 11)?
Solución
B. 1s² 2s² 2p⁶ 3s¹
- Fill orbitals in order: 1s holds 2, 2s holds 2, 2p holds 6.
- That is 10 electrons; the 11th goes into 3s: 1s² 2s² 2p⁶ 3s¹.
Tema: Isotopes
3. Which pair are isotopes?
Solución
A. ¹²C and ¹⁴C
- Isotopes are atoms of the same element with different numbers of neutrons.
- ¹²C and ¹⁴C are both carbon (6 protons) with 6 and 8 neutrons.
Tema: Chemical bonding
4. What type of bond holds sodium chloride together?
Solución
D. Ionic (electrovalent)
- Sodium gives one electron to chlorine, forming Na⁺ and Cl⁻ ions.
- The attraction between oppositely charged ions is an ionic bond.
Tema: Acids and bases
5. Find the pH of 0.01 mol/dm³ hydrochloric acid.
Solución
C. 2
- HCl is a strong acid, so [H⁺] = 0.01 = 10⁻² mol/dm³.
- pH = −log[H⁺] = 2.
Tema: Gas volumes
6. What volume do 2 moles of oxygen occupy at s.t.p.? (Molar volume = 22.4 dm³)
Solución
B. 44.8 dm³
- Volume = moles × molar volume.
- = 2 × 22.4 = 44.8 dm³.
Tema: Redox
7. What is the oxidation number of manganese in KMnO₄?
Solución
A. +7
- K is +1 and each O is −2, and the compound is neutral.
- 1 + Mn + 4(−2) = 0, so Mn = +7.
Tema: Tests for gases
8. Which gas turns limewater milky?
Solución
D. Carbon(IV) oxide
- CO₂ reacts with limewater, Ca(OH)₂, to form insoluble calcium carbonate.
- The white precipitate makes the limewater milky.
Tema: Chemical equilibrium
9. For N₂ + 3H₂ ⇌ 2NH₃ (exothermic), what happens to the yield of ammonia when the pressure is increased?
Solución
C. It increases
- The left side has 4 moles of gas and the right side has 2.
- Higher pressure favours the side with fewer gas moles, so more NH₃ forms.
Tema: Organic chemistry
10. What is the IUPAC name of CH₃CH₂OH?
Solución
B. Ethanol
- Two carbon atoms gives the stem eth-.
- The −OH group makes it an alkanol, so the name ends in -ol: ethanol.
Tema: Organic chemistry
11. Which functional group is found in alkanoic acids?
Solución
A. −COOH
- Alkanoic acids such as ethanoic acid contain the carboxyl group.
- The carboxyl group is −COOH.
Tema: Water
12. Which type of hardness can be removed by boiling?
Solución
D. Temporary hardness, caused by calcium hydrogencarbonate
- Boiling decomposes calcium hydrogencarbonate: Ca(HCO₃)₂ → CaCO₃ + H₂O + CO₂.
- The calcium ions leave as insoluble CaCO₃, so temporary hardness is removed.
Tema: Electrolysis
13. How many faradays are needed to deposit 1 mole of copper from Cu²⁺ ions?
Solución
C. 2
- Cu²⁺ + 2e⁻ → Cu.
- Each mole of copper needs 2 moles of electrons, which is 2 faradays.
Tema: Empirical formula
14. A compound contains 40% carbon, 6.7% hydrogen and 53.3% oxygen by mass. Find its empirical formula. (C = 12, H = 1, O = 16)
Solución
B. CH₂O
- Divide by the relative atomic masses: C 40 ÷ 12 = 3.33, H 6.7 ÷ 1 = 6.7, O 53.3 ÷ 16 = 3.33.
- Divide by the smallest (3.33): C 1, H 2, O 1.
- Empirical formula: CH₂O.
Tema: Reaction rates
15. How does a catalyst increase the rate of a reaction?
Solución
A. It lowers the activation energy
- A catalyst provides another reaction pathway with a lower activation energy.
- More particles have enough energy to react, so the rate increases. The catalyst is not used up.