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post-utme2020chemistry
Q1. Liquid black soap is made by boiling palm oil with liquid extract of ash. The function of the ash is to provide the?
AAcid
BEster of alkanoic acid
CAlkali
DAlkanol
Correct Answer: C
Soap is made by saponification — the reaction of a fat or oil with a strong alkali. Ash extract contains potassium carbonate and potassium hydroxide, which are alkaline. The ash provides the alkali needed to react with palm oil (triglycerides) to form soap (potassium salts of fatty acids) and glycerol.
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post-utme2020chemistry
Q2. The general formula for the Alkanals is?
AR₂CO
BRCHO
CROH
DRCOOR
Correct Answer: B
Alkanals are aldehydes containing the functional group -CHO at the end of the carbon chain. The general formula is RCHO, where R is an alkyl group. R₂CO represents ketones (alkanones), ROH represents alcohols (alkanols), and RCOOR represents esters (alkanoates).
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post-utme2020chemistry
Q3. Four elements P, Q, R and S have atomic numbers of 4, 10, 12 and 14 respectively. Which of these elements is a noble gas?
AP
BQ
CR
DS
Correct Answer: B
Atomic number 10 is neon (Ne), which belongs to Group 18 (noble gases). Its configuration is 1s² 2s² 2p⁶ — a completely filled outer shell. Atomic number 4 is beryllium, 12 is magnesium, and 14 is silicon — none of these are noble gases.
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post-utme2020chemistry
Q4. An electron can be added to a halogen atom to form a halide ion with?
A8 valence electrons
B7 valence electrons
C2 valence electrons
D3 valence electrons
Correct Answer: A
Halogens have 7 valence electrons in their outermost shell. When one electron is added, the halide ion formed has 7 + 1 = 8 valence electrons, achieving a stable noble gas configuration (octet). For example, Cl (7 valence electrons) + e⁻ → Cl⁻ (8 valence electrons).
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post-utme2020chemistry
Q5. The best treatment for a student who accidentally poured conc tetraoxosulphate(vi) on his skin in the laboratory is to wash his skin with?
Acool running water
Bsodium hydroxide solution
Ciodine solution
Dsodium trioxonitrate(v) solution
Correct Answer: A
When concentrated H₂SO₄ contacts skin, the immediate first aid is to flush the affected area with large amounts of cool running water for at least 15–20 minutes. Using NaOH solution could cause a further exothermic neutralisation reaction, worsening the burn. Iodine and sodium trioxonitrate solutions are inappropriate.
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post-utme2020chemistry
Q6. Deliquescent substances are also?
Aefflorescent
Banhydrous
Chygroscopic
Dinsoluble
Correct Answer: C
Deliquescent substances absorb moisture from the atmosphere to the extent of dissolving in it. Hygroscopic substances also absorb moisture from the atmosphere. Deliquescent substances are a specific category of hygroscopic substances, since absorbing moisture until dissolution is an extreme form of hygroscopicity. All deliquescent substances are hygroscopic, but not all hygroscopic substances are deliquescent.
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post-utme2020chemistry
Q7. When a solid substance disappears completely as a gas on heating, the substance is said to have undergone?
ASublimation
BCrystallization
CDistillation
DEvaporation
Correct Answer: A
Sublimation is the direct change of state from solid to gas without passing through the liquid phase. When a solid disappears completely as a gas on heating without melting first, it has sublimed. Examples include iodine, dry ice (solid CO₂), and ammonium chloride.
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post-utme2020chemistry
Q8. When cathode rays are deflected onto the electrode of an electrometer, the instrument becomes?
ABipolar
BNegatively charged
CPositively charged
DNeutral
Correct Answer: B
Cathode rays are streams of electrons, which are negatively charged particles. When these electrons are deflected onto the electrode of an electrometer, they deposit negative charge on it. The electrometer therefore becomes negatively charged. This experiment by J.J. Thomson helped confirm the negative charge of cathode rays.
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post-utme2020chemistry
Q9. What mass of water is produced when 8.0g of hydrogen reacts with excess oxygen?
A8.0g
B16.0g
C36.0g
D72.0g
Correct Answer: D
Equation: 2H₂ + O₂ → 2H₂O. Molar mass of H₂ = 2 g/mol. Moles of H₂ = 8.0 ÷ 2 = 4 mol. From the equation, 2 mol H₂ produces 2 mol H₂O, so 4 mol H₂ produces 4 mol H₂O. Mass of H₂O = 4 × 18 = 72.0 g.
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post-utme2020chemistry
Q10. 32g of anhydrous copper(ii)tetraoxosulphate(vi) dissolved in 1dm³ of water generated 13.0kJ of heat. The heat of solution is?
A26.0kJ/mol
B65.0kJ/mol
C130.0kJ/mol
D260.0kJ/mol
Correct Answer: B
Molar mass of anhydrous CuSO₄ = 64 + 32 + 64 = 160 g/mol. Moles dissolved = 32 ÷ 160 = 0.2 mol. Heat generated = 13.0 kJ for 0.2 mol. Heat of solution per mole = 13.0 ÷ 0.2 = 65.0 kJ/mol.
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post-utme2020chemistry
Q11. The number of molecules of Carbon(iv)Oxide produced when 10.0g of CaCO₃ is treated with 0.2dm³ of 1 Mole of HCl in the equation CaCO₃ + 2HCl ⇒ CaCl₂ + H₂O + CO₂ is?
A1.00 × 10²³
B6.02 × 10²³
C6.02 × 10²²
D6.02 × 10²⁴
Correct Answer: C
Moles of CaCO₃ = 10/100 = 0.1 mol. Moles of HCl = 1 × 0.2 = 0.2 mol. From the equation, 1 mol CaCO₃ needs 2 mol HCl. For 0.1 mol CaCO₃, 0.2 mol HCl is needed — HCl is the limiting reagent exactly. Moles of CO₂ produced = 0.1 mol. Number of molecules = 0.1 × 6.02 × 10²³ = 6.02 × 10²².