WAEC Chemistry Practical Tips: Titration, Salt Tests and Safety

Chemistry practical papers are about method and honesty. You are asked to follow a procedure, record what really happens and draw sensible conclusions. Students who practise a few core skills, especially titration and salt analysis, rarely get surprised. This guide covers those skills and the habits that protect marks.

Formats can change from year to year, and some years are "alternative to practical" papers in which you answer questions on described experiments. Check the syllabus and instructions on the official site (waecnigeria.org) and ask your teacher what applies to your centre. Also compare every reaction and colour below with your own textbook and what you see in the lab; reagents and strengths vary.

What the practical tests

Titration: step by step

A titration measures how much of one solution reacts with a known volume of another. Typical WAEC titration questions use an acid and a base, with an indicator.

Equipment

• Burette (holds the solution you add gradually)
• Pipette with a filler (measures a fixed volume of the other solution)
• Conical flask
• White tile
• Indicator
• Beakers and funnel

Procedure

1. Rinse the burette with a little of the solution it will hold, then fill above the zero mark using a funnel. Remove the funnel, and run some solution out to fill the tip and bring the level to a reading on the scale.
2. Rinse the pipette with the solution it will measure. Use it to transfer the exact volume into the conical flask.
3. Add the indicator (a few drops only).
4. Place the flask on a white tile so colour changes are clear.
5. Run a rough titration first: add solution quickly and swirl until the colour changes. This tells you the approximate end-point.
6. Repeat accurately: add the solution quickly up to about 2 cm³ before the rough value, then drop by drop, swirling all the time.
7. Record the burette reading at the end-point, with your eye level with the meniscus.
8. Repeat until you have at least two close readings (your teacher or the paper will state how close).

Indicator colours (common ones)

Check which indicator your question or teacher specifies, and note the end-point colour change you observe.

Recording results

Draw a table with a ruler and give headings and units:

• Read burettes to two decimal places if the paper uses that convention (usually 0.05 cm³ steps), as your instructions say.
• Subtract initial from final to get the titre.
• Average the concordant titres only. Do not include an outlier.

Typical calculation outline

1. Write the balanced equation.
2. Calculate moles of the solution whose concentration you know (moles = concentration × volume in dm³).
3. Use the mole ratio from the equation to find moles of the other reactant.
4. Calculate the unknown concentration (concentration = moles ÷ volume in dm³).
5. If asked, convert to g/dm³ by multiplying by molar mass.

Show every step with units. Method marks are usually given even if the final answer is off.

Qualitative analysis of salts

You are given an unknown salt and asked to identify the cation and anion by tests. Follow the order and instructions in the paper. Add reagents drop by drop, shake gently, and record changes immediately.

Cation tests with sodium hydroxide (common results)

Your syllabus may also include aluminium, lead and ammonium with ammonia solution. Learn the table from your textbook and verify each result in the lab where possible.

Anion and gas tests (common)

Gas tests to know:

• Carbon dioxide turns limewater milky.
• Hydrogen burns with a "pop" when a lit splint is brought near.
• Oxygen relights a glowing splint.
• Ammonia turns damp red litmus paper blue and has a sharp smell.

Write results clearly

Do not write "copper" as an observation. The observation is the colour. Do not guess before you have evidence; if a result is unclear, say so and use further tests.

Heating, filtering and crystallisation

• Heating a solid: Hold the test tube at an angle with a holder, move it gently, and point it away from people. Note colour changes, gases and condensation.
• Filtering: Fold the filter paper to fit the funnel, wet it, pour along a glass rod, and keep the level below the paper's edge.
• Evaporation and crystallisation: Heat gently until a small portion of liquid remains, then allow to cool.
• Always record both the apparatus used and what you observed.

Safety

Follow your lab rules and instructions from invigilators and supervisors.

Time and presentation

Plan your time before starting. If a question has three parts (titration, calculation, qualitative analysis), spend time proportionally to the marks. Use a ruler for tables, write neatly, and check units and significant figures. Leave a few minutes at the end to read through and add anything missed.

A practice plan

If your school lab has limited supplies, use diagrams and videos from your teacher, and practise the calculations at home. Many marks lie in tables, calculations and explanations, which need no equipment.

Common mistakes

• Starting the burette reading from a non-zero point but forgetting to subtract
• Adding too much indicator
• Not rinsing equipment with the correct solution
• Reading the meniscus from above or below, not at eye level
• Writing inferences in the observation column
• Forgetting units

Next steps

Revise the theory behind practicals using how to pass WAEC Chemistry, compare drawing and recording habits in our Biology practical tips and graph skills in the Physics practical tips. Then check your understanding with free WAEC Chemistry practice on ExamPadi, which covers the mole concept, acids and bases and other practical-linked theory.