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JAMB and WAEC Chemistry questions: Chemical combination

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

AllJAMBWAEC
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 41· Chemical combination· WAEC

    What mass of calcium oxide is formed by heating 50 g of calcium trioxocarbonate(IV) to constant mass? [Ca = 40, C = 12, O = 16]

    Explanation and discussion

  2. Question 42· Chemical combination· WAEC

    What is the relative molecular mass of CO₂? (C = 12, O = 16)

    Explanation and discussion

  3. Question 43· Chemical combination· JAMB

    Find the mass of 3.01 × 10²³ atoms of sodium. (Na = 23; Avogadro's constant = 6.02 × 10²³ mol⁻¹)

    Explanation and discussion

  4. Question 44· Chemical combination· JAMB

    0.5 g of a gas occupies 280 cm³ at s.t.p. Find its molar mass. [molar volume = 22.4 dm³]

    Explanation and discussion

  5. Question 45· Chemical combination· JAMB

    How many moles are in 11 g of carbon(IV) oxide? (C = 12, O = 16)

    Explanation and discussion

  6. Question 46· Chemical combination· JAMB

    How many molecules are in 0.5 mol of water? (Avogadro's constant = 6.02 × 10²³ mol⁻¹)

    Explanation and discussion

  7. Question 47· Chemical combination· WAEC

    Elements combine in a fixed ratio by mass to form a particular compound. This is the law of

    Explanation and discussion

  8. Question 48· Chemical combination· WAEC

    The number of moles in 4.4 g of CO₂ (C = 12, O = 16) is

    Explanation and discussion

  9. Question 49· Chemical combination· JAMB

    A compound contains 2.4 g of carbon and 0.6 g of hydrogen. Find its empirical formula. (C = 12, H = 1)

    Explanation and discussion

  10. Question 50· Chemical combination· WAEC

    How many moles are there in 9.8 g of tetraoxosulphate(VI) acid, H₂SO₄? [H = 1, S = 32, O = 16]

    Explanation and discussion

  11. Question 51· Chemical combination· WAEC

    The mass of 0.5 mol of NaOH (Na = 23, O = 16, H = 1) is

    Explanation and discussion

  12. Question 52· Chemical combination· JAMB

    A compound contains 80% carbon and 20% hydrogen by mass, and its molar mass is 30 g/mol. Find its molecular formula. [C = 12, H = 1]

    Explanation and discussion

  13. Question 53· Chemical combination· JAMB

    A compound has the empirical formula CH₂O and a relative molecular mass of 180. Find its molecular formula. (C = 12, H = 1, O = 16)

    Explanation and discussion

  14. Question 54· Chemical combination· JAMB

    The statement that in a closed system the total mass of reactants equals the total mass of products is the law of

    Explanation and discussion

  15. Question 55· Chemical combination· JAMB

    Find the molar mass of sodium trioxocarbonate(IV), Na₂CO₃. (Na = 23, C = 12, O = 16)

    Explanation and discussion

  16. Question 56· Chemical combination· JAMB

    Find the mass of 0.25 mol of calcium trioxocarbonate(IV), CaCO₃. (Ca = 40, C = 12, O = 16)

    Explanation and discussion

  17. Question 57· Chemical combination· WAEC

    Calculate the percentage by mass of nitrogen in NH₃. (N = 14, H = 1)

    Explanation and discussion

  18. Question 58· Chemical combination· JAMB

    In 2H₂ + O₂ → 2H₂O, what volume of oxygen is needed to burn 40 cm³ of hydrogen at the same temperature and pressure?

    Explanation and discussion

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