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WAEC WASSCE 2017

WAEC Chemistry 2017 past questions

6 objective questions from the 2017 WAEC Chemistry paper. Answer each one, then reveal the answer and explanation.

All WAEC Chemistry past questions

  1. Question 1

    Chemical symbols

    What is the chemical symbol of potassium?

    1. Option A: K
    2. Option B: P
    3. Option C: Po
    4. Option D: Pt
    Show the answer to question 1

    Answer: A, K

    Potassium is K, from its Latin name kalium.

  2. Question 2

    Mole concept

    How many moles are there in 91.25 g of hydrogen chloride (HCl)? [H = 1, Cl = 35.5]

    1. Option A: 5 mol
    2. Option B: 1.25 mol
    3. Option C: 2.5 mol
    4. Option D: 25 mol
    Show the answer to question 2

    Answer: C, 2.5 mol

    Moles = mass ÷ molar mass = 91.25 ÷ 36.5 = 2.5 mol.

  3. Question 3

    Atomic structure

    An atom of potassium has atomic number 19 and mass number 39. How many neutrons are in its nucleus?

    1. Option A: 39
    2. Option B: 19
    3. Option C: 58
    4. Option D: 20
    Show the answer to question 3

    Answer: D, 20

    Neutrons = mass number − atomic number = 39 − 19 = 20.

  4. Question 4

    Periodic table

    In which group of the periodic table is boron found?

    1. Option A: Group V
    2. Option B: Group III
    3. Option C: Group VI
    4. Option D: Group VII
    Show the answer to question 4

    Answer: B, Group III

    Boron (configuration 2, 3) is in Group III.

  5. Question 5

    Gas laws

    A fixed mass of gas occupies 720 cm³ at a pressure of 5 atm. What volume will it occupy at 2 atm if the temperature stays constant?

    1. Option A: 288 cm³
    2. Option B: 720 cm³
    3. Option C: 7200 cm³
    4. Option D: 1800 cm³
    Show the answer to question 5

    Answer: D, 1800 cm³

    By Boyle's law, P₁V₁ = P₂V₂, so V₂ = 5 × 720 ÷ 2 = 1800 cm³.

  6. Question 6

    Acids, bases and salts

    Which acid is present in the sting of an ant?

    1. Option A: Methanoic acid
    2. Option B: Ethanoic acid
    3. Option C: Citric acid
    4. Option D: Oxalic acid
    Show the answer to question 6

    Answer: A, Methanoic acid

    Ant stings contain methanoic (formic) acid.

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