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WAEC Chemistry questions: Chemical combination

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

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All topicsAcids, bases and salts · 26Air · 16Atomic structure and bonding · 26Chemical combination · 27Chemical equilibrium · 16Chemistry and industry · 17Electrolysis · 19Energy changes · 16Environmental pollution · 15Kinetic theory of matter and gas laws · 18Metals and their compounds · 23Non-metals and their compounds · 22Organic compounds · 29Oxidation and reduction · 19Rates of chemical reaction · 16Separation of mixtures and purification · 18Solubility · 16Water · 18

  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· WAEC

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

    Explanation and discussion

  3. Question 3· 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

  4. Question 4· Chemical combination· WAEC

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

    Explanation and discussion

  5. Question 5· Chemical combination· WAEC

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

    Explanation and discussion

  6. Question 6· Chemical combination· WAEC

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

    Explanation and discussion

  7. Question 7· Chemical combination· WAEC

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

    Explanation and discussion

  8. Question 8· Chemical combination· WAEC

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

    Explanation and discussion

  10. Question 10· Chemical combination· WAEC

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

    Explanation and discussion

  11. Question 11· Chemical combination· WAEC

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

    Explanation and discussion

  12. Question 12· Chemical combination· WAEC

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

    Explanation and discussion

  13. Question 13· Chemical combination· WAEC

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

    Explanation and discussion

  14. Question 14· Chemical combination· WAEC

    A compound contains 40% carbon, 6.7% hydrogen and 53.3% oxygen by mass. Find its empirical formula. [C = 12, H = 1, O = 16]

    Explanation and discussion

  15. Question 15· Chemical combination· WAEC

    The relative molecular mass of CO₂ is (C = 12, O = 16)

    Explanation and discussion

  16. Question 16· Chemical combination· WAEC

    The volume of 2 mol of an ideal gas at s.t.p. is

    Explanation and discussion

  17. Question 17· Chemical combination· WAEC

    The percentage of water of crystallisation in CuSO₄·5H₂O (Cu = 64, S = 32, O = 16, H = 1) is

    Explanation and discussion

  18. Question 18· Chemical combination· WAEC

    Avogadro's number of particles is

    Explanation and discussion

  19. Question 19· Chemical combination· WAEC

    How many atoms are present in 0.5 mol of sulphur? [L = 6.02 × 10²³]

    Explanation and discussion

  20. Question 20· Chemical combination· WAEC

    The formula of calcium chloride is

    Explanation and discussion

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