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WAEC WASSCE

WAEC Chemistry past questions and answers

Objective Chemistry questions from past WAEC WASSCE papers, with the answer and a short explanation for each. Try a question, then reveal the answer to check your working.

  1. Question 1

    WAEC 2024Organic chemistry

    What is the molecular formula of butene?

    1. Option A: C₄H₁₀
    2. Option B: C₄H₆
    3. Option C: C₄H₈
    4. Option D: C₄H₉
    Show the answer to question 1

    Answer: C, C₄H₈

    Alkenes follow CₙH₂ₙ, so butene with 4 carbon atoms is C₄H₈.

  2. Question 2

    WAEC 2024Acids, bases and salts

    Which description fits a solution whose pH is 2?

    1. Option A: strongly acidic
    2. Option B: weakly acidic
    3. Option C: neutral
    4. Option D: strongly alkaline
    Show the answer to question 2

    Answer: A, strongly acidic

    The lower the pH below 7, the stronger the acid.

  3. Question 3

    WAEC 2024Gas laws

    A fixed mass of gas occupies 540 cm³ at a pressure of 1 atm. What volume will it occupy at 4 atm if the temperature stays constant?

    1. Option A: 2160 cm³
    2. Option B: 540 cm³
    3. Option C: 270 cm³
    4. Option D: 135 cm³
    Show the answer to question 3

    Answer: D, 135 cm³

    By Boyle's law, P₁V₁ = P₂V₂, so V₂ = 1 × 540 ÷ 4 = 135 cm³.

  4. Question 4

    WAEC 2024Atomic structure

    An atom of neon has atomic number 10 and mass number 20. How many neutrons are in its nucleus?

    1. Option A: 20
    2. Option B: 10
    3. Option C: 30
    4. Option D: 11
    Show the answer to question 4

    Answer: B, 10

    Neutrons = mass number − atomic number = 20 − 10 = 10.

  5. Question 5

    WAEC 2024Electronic configuration

    What is the electronic configuration of fluorine (atomic number 9)?

    1. Option A: 2, 6
    2. Option B: 2, 8
    3. Option C: 2, 7
    4. Option D: 2, 8, 1
    Show the answer to question 5

    Answer: C, 2, 7

    Fill the shells in order, 2 then 8 then 8: fluorine has 9 electrons, arranged 2, 7.

  6. Question 6

    WAEC 2023Electronic configuration

    What is the electronic configuration of beryllium (atomic number 4)?

    1. Option A: 2, 1
    2. Option B: 2, 3
    3. Option C: 2, 2
    4. Option D: 2, 4
    Show the answer to question 6

    Answer: C, 2, 2

    Fill the shells in order, 2 then 8 then 8: beryllium has 4 electrons, arranged 2, 2.

  7. Question 7

    WAEC 2023Atomic structure

    An atom of nitrogen has atomic number 7 and mass number 14. How many neutrons are in its nucleus?

    1. Option A: 7
    2. Option B: 14
    3. Option C: 21
    4. Option D: 8
    Show the answer to question 7

    Answer: A, 7

    Neutrons = mass number − atomic number = 14 − 7 = 7.

  8. Question 8

    WAEC 2023Chemical symbols

    What is the chemical symbol of antimony?

    1. Option A: Sb
    2. Option B: An
    3. Option C: A
    4. Option D: At
    Show the answer to question 8

    Answer: A, Sb

    Antimony is Sb, from its Latin name stibium.

  9. Question 9

    WAEC 2023Gas laws

    A fixed mass of gas occupies 480 cm³ at a pressure of 3 atm. What volume will it occupy at 2 atm if the temperature stays constant?

    1. Option A: 320 cm³
    2. Option B: 480 cm³
    3. Option C: 720 cm³
    4. Option D: 2880 cm³
    Show the answer to question 9

    Answer: C, 720 cm³

    By Boyle's law, P₁V₁ = P₂V₂, so V₂ = 3 × 480 ÷ 2 = 720 cm³.

  10. Question 10

    WAEC 2023Organic chemistry

    What is the molecular formula of propene?

    1. Option A: C₃H₆
    2. Option B: C₃H₈
    3. Option C: C₃H₄
    4. Option D: C₃H₇
    Show the answer to question 10

    Answer: A, C₃H₆

    Alkenes follow CₙH₂ₙ, so propene with 3 carbon atoms is C₃H₆.

More Chemistry: JAMB Chemistry past questions.

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