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JAMB and WAEC Chemistry questions: Chemical combination

58 questions with answers and explanations. Tap an option to check yourself.

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All topicsAcids, bases and salts · 58Air · 37Atomic structure and bonding · 59Chemical combination · 58Chemical equilibrium · 37Chemistry and industry · 35Electrolysis · 41Energy changes · 38Environmental pollution · 32Kinetic theory of matter and gas laws · 45Metals and their compounds · 47Non-metals and their compounds · 45Organic compounds · 72Oxidation and reduction · 41Rates of chemical reaction · 38Separation of mixtures and purification · 42Solubility · 36Water · 39

  1. Question 1· Chemical combination· WAEC

    Calculate the percentage by mass of nitrogen in ammonium trioxonitrate(V), NH₄NO₃. [N = 14, H = 1, O = 16]

    Explanation and discussion

  2. Question 2· Chemical combination· JAMB

    What mass of oxygen combines with 4 g of hydrogen to form water? (H = 1, O = 16)

    Explanation and discussion

  3. Question 3· Chemical combination· WAEC

    What volume does 0.25 mol of carbon(IV) oxide occupy at s.t.p.? [molar volume = 22.4 dm³]

    Explanation and discussion

  4. Question 4· Chemical combination· JAMB

    Find the percentage by mass of nitrogen in NH₄NO₃. (N = 14, H = 1, O = 16)

    Explanation and discussion

  5. Question 5· Chemical combination· JAMB

    In the reaction 2KClO₃ → 2KCl + 3O₂, how many moles of oxygen are produced from 2 mol of KClO₃?

    Explanation and discussion

  6. Question 6· Chemical combination· JAMB

    How many molecules are in 4.4 g of carbon(IV) oxide? [C = 12, O = 16, L = 6.0 × 10²³]

    Explanation and discussion

  7. Question 7· Chemical combination· WAEC

    Pure water from any source always contains hydrogen and oxygen in the mass ratio 1 : 8. This illustrates the law of

    Explanation and discussion

  8. Question 8· Chemical combination· WAEC

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

    Explanation and discussion

  9. Question 9· Chemical combination· WAEC

    The law of conservation of mass states that in a chemical reaction

    Explanation and discussion

  10. Question 10· Chemical combination· WAEC

    How many moles are in 36 g of water? (H = 1, O = 16)

    Explanation and discussion

  11. Question 11· Chemical combination· WAEC

    The empirical formula of a compound whose molecular formula is C₂H₆ is

    Explanation and discussion

  12. Question 12· Chemical combination· WAEC

    In 2Mg + O₂ → 2MgO, how many moles of magnesium oxide are formed from 4 mol of magnesium?

    Explanation and discussion

  14. Question 14· Chemical combination· WAEC

    Calculate the mass of 0.2 mol of NaCl. (Na = 23, Cl = 35.5)

    Explanation and discussion

  15. Question 15· Chemical combination· JAMB

    The law of definite proportions states that

    Explanation and discussion

  16. Question 16· Chemical combination· JAMB

    How many molecules are in 2 mol of nitrogen gas? (Avogadro's constant = 6.02 × 10²³ mol⁻¹)

    Explanation and discussion

  17. Question 17· Chemical combination· JAMB

    What mass of sodium hydroxide is needed to prepare 250 cm³ of a 0.2 mol/dm³ solution? [Na = 23, O = 16, H = 1]

    Explanation and discussion

  18. Question 18· Chemical combination· WAEC

    In the equation 2H₂ + O₂ → 2H₂O, the mass of water formed from 4 g of hydrogen is

    Explanation and discussion

  19. Question 19· Chemical combination· WAEC

    When the equation aAl + bO₂ → cAl₂O₃ is balanced, a, b and c are

    Explanation and discussion

  20. Question 20· Chemical combination· WAEC

    A hydrocarbon contains 85.7% carbon by mass (C = 12, H = 1). Its empirical formula is

    Explanation and discussion

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