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JAMB UTME Chemistry 2019 past questions and answers

This 2019 JAMB UTME Chemistry set has 40 practice questions. Try these 5 free sample questions, tap a question to reveal the answer and explanation. Then practise the whole 2019 set with instant marking.

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Sample JAMB UTME Chemistry 2019 questions

1. Across Period 3 from sodium to chlorine, the atomic radius generally decreases because
  1. the number of occupied electron shells increases
  2. the nuclear charge increases while electrons are added to the same shell
  3. the atoms lose all their valence electrons
  4. the shielding effect increases more rapidly than nuclear charge

Answer: B. the nuclear charge increases while electrons are added to the same shell

Across a period, proton number rises while added electrons enter the same principal shell, so the stronger attraction draws the electron cloud closer.

2. Which statement best explains why molten sodium chloride conducts electricity whereas solid sodium chloride does not?
  1. The solid contains no charged particles
  2. Electrons become free only when the salt is heated
  3. The ions are mobile in the molten salt but fixed in the solid lattice
  4. The molten salt contains covalent molecules

Answer: C. The ions are mobile in the molten salt but fixed in the solid lattice

Ionic solids have ions held in fixed positions, but melting lets the ions move and carry charge.

3. An element consists of 75% of an isotope of mass 35 and 25% of an isotope of mass 37. What is its relative atomic mass?
  1. 35.0
  2. 36.0
  3. 37.0
  4. 35.5

Answer: D. 35.5

The weighted mean is (0.75 x 35) + (0.25 x 37) = 35.5.

4. What volume will 0.25 mol of an ideal gas occupy at s.t.p. if the molar gas volume is 22.4 dm3 mol^-1?
  1. 5.6 dm3
  2. 11.2 dm3
  3. 22.4 dm3
  4. 89.6 dm3

Answer: A. 5.6 dm3

Volume = amount x molar volume = 0.25 x 22.4 = 5.6 dm3.

5. A compound contains 40.0% carbon, 6.7% hydrogen and 53.3% oxygen by mass. What is its empirical formula? (C=12, H=1, O=16)
  1. C2H4O2
  2. CH2O
  3. CHO
  4. C2H2O

Answer: B. CH2O

In 100 g, the mole ratios are 40/12, 6.7/1 and 53.3/16, which reduce approximately to 1:2:1.

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