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JAMB UTME Chemistry 2021 past questions and answers

This 2021 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 2021 set with instant marking.

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Sample JAMB UTME Chemistry 2021 questions

1. Photochemical smog is formed mainly when sunlight acts on nitrogen oxides and
  1. sulfur crystals
  2. unburnt hydrocarbons
  3. water vapour
  4. carbonates

Answer: B. unburnt hydrocarbons

Sunlight drives reactions between nitrogen oxides and unburnt hydrocarbons to form photochemical smog.

2. The main atmospheric gases responsible for acid rain are
  1. sulfur dioxide and nitrogen oxides
  2. carbon monoxide and methane
  3. hydrogen and oxygen
  4. argon and neon

Answer: A. sulfur dioxide and nitrogen oxides

Sulfur dioxide and nitrogen oxides dissolve and react in atmospheric moisture to form acids.

3. What volume of 0.20 mol dm^-3 sodium hydroxide is required to neutralize 25.0 cm^3 of 0.10 mol dm^-3 sulfuric acid?
  1. 12.5 cm^3
  2. 20.0 cm^3
  3. 25.0 cm^3
  4. 50.0 cm^3

Answer: C. 25.0 cm^3

The reaction H2SO4 + 2NaOH gives 0.005 mol NaOH, which occupies 0.025 dm^3 at 0.20 mol dm^-3.

4. Which method is most suitable for preparing a pure sample of insoluble lead(II) sulfate?
  1. Titrating lead with dilute sulfuric acid
  2. Heating lead sulfate crystals to dryness
  3. Evaporating a solution of lead sulfate
  4. Mixing solutions of a soluble lead salt and a soluble sulfate

Answer: D. Mixing solutions of a soluble lead salt and a soluble sulfate

Mixing suitable soluble salts precipitates insoluble lead(II) sulfate, which can then be filtered and washed.

5. What is the oxidation number of chromium in K2Cr2O7?
  1. +6
  2. +3
  3. +7
  4. +12

Answer: A. +6

For a neutral compound, 2(+1) + 2x + 7(-2) = 0, giving x = +6.

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