JAMB and WAEC Chemistry questions

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

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

Question 201· Chemical combination· WAEC
Elements combine in a fixed ratio by mass to form a particular compound. This is the law of
Explanation and discussion
Question 202· Chemical combination· WAEC
The number of moles in 4.4 g of CO₂ (C = 12, O = 16) is
Explanation and discussion
Question 203· 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
Question 204· 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
Question 205· Chemical combination· WAEC
The mass of 0.5 mol of NaOH (Na = 23, O = 16, H = 1) is
Explanation and discussion
Question 206· 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
Question 207· 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
Question 208· 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
Question 209· Chemical combination· JAMB
Find the molar mass of sodium trioxocarbonate(IV), Na₂CO₃. (Na = 23, C = 12, O = 16)
Explanation and discussion
Question 210· Chemical combination· JAMB
Find the mass of 0.25 mol of calcium trioxocarbonate(IV), CaCO₃. (Ca = 40, C = 12, O = 16)
Explanation and discussion
Question 211· Chemical combination· WAEC
Calculate the percentage by mass of nitrogen in NH₃. (N = 14, H = 1)
Explanation and discussion
Question 212· 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
Question 213· Chemical equilibrium· WAEC
For CO(g) + H₂O(g) ⇌ CO₂(g) + H₂(g), increasing the pressure
Explanation and discussion
Question 214· Chemical equilibrium· WAEC
For 2SO₂ + O₂ ⇌ 2SO₃ (exothermic), lowering the temperature
Explanation and discussion
Question 215· Chemical equilibrium· WAEC
For N₂ + 3H₂ ⇌ 2NH₃, removing ammonia as it forms
Explanation and discussion
Question 216· Chemical equilibrium· JAMB
Adding a catalyst to a reaction at equilibrium
Explanation and discussion
Question 217· Chemical equilibrium· JAMB
For H₂(g) + I₂(g) ⇌ 2HI(g), increasing the pressure
Explanation and discussion
Question 218· Chemical equilibrium· JAMB
For the equilibrium N₂ + 3H₂ ⇌ 2NH₃ (ΔH negative), the yield of ammonia is increased by:
Explanation and discussion
Question 219· Chemical equilibrium· JAMB
A reversible reaction is at equilibrium when
Explanation and discussion
Question 220· Chemical equilibrium· JAMB
For a reversible reaction whose forward reaction is exothermic, lowering the temperature
Explanation and discussion

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JAMB and WAEC Chemistry questions

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

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

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

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

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

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]

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

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

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

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

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

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

For CO(g) + H₂O(g) ⇌ CO₂(g) + H₂(g), increasing the pressure

For 2SO₂ + O₂ ⇌ 2SO₃ (exothermic), lowering the temperature

For N₂ + 3H₂ ⇌ 2NH₃, removing ammonia as it forms

Adding a catalyst to a reaction at equilibrium

For H₂(g) + I₂(g) ⇌ 2HI(g), increasing the pressure

For the equilibrium N₂ + 3H₂ ⇌ 2NH₃ (ΔH negative), the yield of ammonia is increased by:

A reversible reaction is at equilibrium when

For a reversible reaction whose forward reaction is exothermic, lowering the temperature