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JAMB UTME 2015

JAMB Chemistry 2015 past questions

6 objective questions from the 2015 JAMB Chemistry paper. Answer each one, then reveal the answer and explanation.

All JAMB Chemistry past questions

  1. Question 1

    Organic chemistry

    What is the molecular formula of heptane?

    1. Option A: C₇H₁₆
    2. Option B: C₇H₁₄
    3. Option C: C₇H₁₂
    4. Option D: C₇H₁₅
    Show the answer to question 1

    Answer: A, C₇H₁₆

    Alkanes follow CₙH₂ₙ₊₂, so heptane with 7 carbon atoms is C₇H₁₆.

  2. Question 2

    Electronic configuration

    What is the electronic configuration of phosphorus (atomic number 15)?

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

    Answer: A, 2, 8, 5

    Fill the shells in order, 2 then 8 then 8: phosphorus has 15 electrons, arranged 2, 8, 5.

  3. Question 3

    Atomic structure

    An atom of magnesium has atomic number 12 and mass number 24. How many neutrons are in its nucleus?

    1. Option A: 12
    2. Option B: 24
    3. Option C: 36
    4. Option D: 13
    Show the answer to question 3

    Answer: A, 12

    Neutrons = mass number − atomic number = 24 − 12 = 12.

  4. Question 4

    Mole concept

    How many moles are there in 9 g of water (H₂O)? [H = 1, O = 16]

    1. Option A: 1 mol
    2. Option B: 0.25 mol
    3. Option C: 0.5 mol
    4. Option D: 5 mol
    Show the answer to question 4

    Answer: C, 0.5 mol

    Moles = mass ÷ molar mass = 9 ÷ 18 = 0.5 mol.

  5. Question 5

    Acids, bases and salts

    Blue litmus paper dipped in an acid turns

    1. Option A: blue
    2. Option B: green
    3. Option C: red
    4. Option D: yellow
    Show the answer to question 5

    Answer: C, red

    Acids turn blue litmus red.

  6. Question 6

    Gas laws

    A fixed mass of gas occupies 180 cm³ at a pressure of 4 atm. What volume will it occupy at 2 atm if the temperature stays constant?

    1. Option A: 360 cm³
    2. Option B: 90 cm³
    3. Option C: 180 cm³
    4. Option D: 1440 cm³
    Show the answer to question 6

    Answer: A, 360 cm³

    By Boyle's law, P₁V₁ = P₂V₂, so V₂ = 4 × 180 ÷ 2 = 360 cm³.

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