waec model questions vol1 2025 chemistry | Practical

Are you preparing for waec model questions vol1 exams? Reviewing past questions is one of the most effective ways to guarantee a high score. This practice hub features authentic 2025 chemistry (Practical) questions designed to simulate the real exam environment.

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Question 1
In an experiment to determine the percentage composition of a compound containing carbon, hydrogen, and oxygen, a sample weighing 5.00 g is combusted completely in excess oxygen. The products of combustion are collected, and the mass of carbon dioxide produced is found to be 11.00 g, while the mass of water produced is 4.50 g. Using this data, calculate the percentage composition of each element in the compound. Show all your workings.
Question Parts
(a)
Calculate the moles of carbon in the carbon dioxide produced.
(b)
Determine the moles of water produced and the moles of hydrogen in the water.
(c)
Using the moles calculated, find the mass of carbon, hydrogen, and oxygen in the original compound. Hence, calculate the percentage composition of each element.
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Question 2
A student is investigating the properties of metals and non-metals. They conduct a series of experiments to test the conductivity, malleability, and reactivity of various elements. Describe the procedure for testing the conductivity of a metal and a non-metal. Include the expected observations and the significance of the results.
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Question 3
A student is investigating the properties of ionic compounds. She prepares a solution of sodium chloride (NaCl) in water and performs a conductivity test. She also prepares a solution of glucose (C6H12O6) in water and conducts a similar test. (a) Describe the expected observations for each solution regarding conductivity and explain the underlying reasons for these observations. (b) The student then decides to evaporate the water from the sodium chloride solution to obtain the solid salt. Explain the process she would follow and the changes that occur during evaporation. (c) If the student were to repeat the experiment using potassium chloride (KCl) instead of sodium chloride, predict whether the conductivity observations would change and justify your answer.
Question Parts
(a)
Describe the expected observations for each solution regarding conductivity and explain the underlying reasons for these observations.
(b)
Explain the process she would follow and the changes that occur during evaporation.
(c)
Predict whether the conductivity observations would change and justify your answer.
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Question 4
A student is performing a titration experiment to determine the concentration of hydrochloric acid (HCl) using a sodium hydroxide (NaOH) solution of known concentration. The balanced chemical equation for the reaction is: HCl(aq) + NaOH(aq) → NaCl(aq) + H2O(l) (a) Describe the procedure the student would follow to carry out the titration, including the setup of apparatus and the indicators used. (b) If the student used 25.0 mL of HCl and titrated it with 0.1 M NaOH, and the endpoint was reached at 30.0 mL of NaOH solution, calculate the concentration of the hydrochloric acid solution. (c) Discuss possible sources of error in this experiment and how they could be minimized.
Question Parts
(a)
Describe the procedure the student would follow to carry out the titration, including the setup of apparatus and the indicators used.
(b)
If the student used 25.0 mL of HCl and titrated it with 0.1 M NaOH, and the endpoint was reached at 30.0 mL of NaOH solution, calculate the concentration of the hydrochloric acid solution.
(c)
Discuss possible sources of error in this experiment and how they could be minimized.
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