Waec chemistry practical examination

WAEC examinatoin chemistry practical, how it looks like, questions and solution to solve it.

 

The WAEC practical exam is among the hardest in WAEC. This practical alone contains 40% of your WAEC chemistry result.

 

This practical is to test your knowledge of chemistry. On the practical examination, you will be given some unknown salt solution and they will expect you to conduct an experiment to find out the name, volume, and mass of the salt given to you.

 

The examination is a tough one for students who showed less interest in learning chemistry during school lectures, but it is very simple for brilliant students.

 

All the questions you see on the WAEC chemistry practical must be under qualitative and quantitative analysis.

 

All science students that are trying to write the WAEC should focus on learning how to solve WAEC chemistry practical questions.

Here I will be teaching you the solutions to solve the WAEC chemistry practical during the examination and what to do if you have low knowledge of chemistry.

In order to solve this practical examination, you need a higher knowledge of chemistry. The example above is called titration.

Procedure to follow when solving WAEC chemistry practical

Here is the procedure to follow when solving WAEC chemistry practical questions.

 

  • Check the instructions given to you in the questions.

 

  • Put the required amount of salt solution they asked you to put in the appropriate instruments.

 

  • Titrate and write down your results.

Items needed for writing WAEC chemistry practical examination

Some materials used on the day of the practical examination, as well as precautions to take when using some of them.

  • weighting balance
  • Chemical balance
  • pipette
  • burette
  • filter paper
  •  retort stand.
  • funnel
  • white tile
  • A standard volumetric flask
  • conical flask.

Precautions for using some of this WAEC chemistry practical equipments

Take precautions when using a pipette, burette, or conical flask to avoid any damages on the examination Hall.

 

Pippette precautions for using a pipette in the examination hall

 

1) Rinse the pipette with the solution to be measured, i.e. base

 

2) Avoid the formation of air bubbles in the pipette.

 

3) Check that the reading mark is at eye level with your eyes.

 

4) Do not blow the pipette’s last drop.

 

 

precautions for using the burette in the examination hall.

 

1) After rinsing with distilled water, rinse the burette with the acid.

 

2) Check that the burette jet is fully charged.

 

3) Avoid air bubbles in the burette the same way you did with the pipette.

 

4) To avoid parallax errors, take your burette reading with your eyes at the same level as the meniscus.

 

5) Check that the burette is not leaking in order to prevent damage to the examination hall.

 

6) Before taking your reading, remove the funnel.

 

7) Avoid erratic burette reading.

 

precautions for using the conical flask in the examination hall.

 

1) Rinse it with distilled water rather than any of the solutions used in the practical.

 

2) wash down with distilled water any drops of the solution that stuck to the side of the conical flask during the practical.

 

How can I learn WAEC practical?

 

 

Here are the main things to do if you wish to learn the WAEC practical, even if you don’t have a chemistry practical teacher.

Get a good text book.

A chemistry practical text book is not too expensive to purchase for serious science students.

 

As I said before, the questions must come from volumetric and qualitative analysis. There are numerous topics in chemistry that require practicals, like electrolysis, organic chemistry, and others, but the items required in order to conduct a successful practical on those topics are not cheaply available.

 

Study all the laboratory instruments, their names and their functions. Check the instruments above; that’s what you will use on the examination practical day.

 

 

 

 

Weac is repeating past questions, particularly in chemistry practicals; they are aware that you are aware, but they continue to repeat them.They don’t want you to fail, they want you to master the topic and be ready for your questions before the exam day.

 

Ask your tutor questions if you’re having problems understanding any practical topic.

 

An example of a WAEC chemistry practical question

 

Let’s now look at how WAEC chemistry practical questions are being set.

 

Seventy percent of the questions in the practical examination are from the chemistry topic “volumetric and qualitative analysis.”

 

It always contains three questions, in which you are expected to answer all of them.

 

Here is one example of how a WAEC chemistry practical examination is being set and a solution to tackle it.

 

EXPERIMENT

Using a standard solution, one can determine the concentration of hydrochloric acid.

 

requirements.

 

Standard sodium hydroxide solution, 50cm3 burette, 25cm3 pipette, methyl orange indicator

 

METHOD

 

Fill the burette with hydrochloric acid and adjust it’s level to the zero mark. Pipette 25cm3 of the base into a conical flask and add two drops of the indicator. Note the volume of acid that neutralizes the base, tabulate your results, and solve the additional questions.

 

Please comment below if you need wish to learn WAEC practical, state your question below.

WAEC 2022 Chemistry Practical Questions

(1.) Volume of burrete = 50.00cm³

Volume of pipette = 25.00cm³

Indicator = Methyl orange.

TABULATE

Final burette readings (cm³); 37.50 | 22.50 | 37.50 | 44.50

Initial burette readings(cm³); 0.00 | 0.00 | 0.00 | 0.00

Volume f Acid used (cm³); 37.50 | 22.50 | 22.50 | 22.50

Volume of A used = 1st + 2nd + 3rd/3

= 22.50+22.50+22.50/3

Average volume of A used = 22.50cm³.

(1bi)

Concentration of A ( CA )?

2.03g in 500cm³ of solution

Volume = 500cm³/1000 = 0.500dm³

In g/dm³ = 2.03/0.5 = 4.06g/dm³

To find concentration in mol/dm³

Conc. of A in mol/dm³ = Conc. of A in g/dm³/Molar mass.

Conc. of A in mol/dm³ = 4.06/36.5

= 0.1112mol/dm³

Molar mass of A (HCL) = 1+35.5 = 36.5g/mol.

(1bii)

Number of mole of the Acid in average titre

Na = CaVa

= 0.1112 × 22.50

= 2.52moles.

(1biii)

Nb= ? Na= 3, Ca= 0.1112mol/dm³, Cb = 0.12mol/dm³ , Va = 22.50cm³, Vb = 50.00cm³.

CaVa/CbVb= nA/nB

0.1112×22.50/0.12×50 = 3/nB

nB × 2.502 = 18 nB = 18/2.502 = :. nB = 7.194moles = 7moles(approx.)

(1biv)

Mole ratio of Acid to base

nA:nB = 7:3

(2a)

Test; C + 10cm³ of distilled water + filter.

Observation; C dissolves partially to give a light green solution. Blue filtrate and green residue.

Inference; C is a mixture of soluble and insoluble salt.

(2bi)

Test; 2cm³ of filtrate + NaOH in drops in excess.

Observation; Blue precipitate remains.

Inference; CU²+ is present.

(2bii)

Test; 2bi + warm.

Observation; a colourless gas with a choking smell that turns moist red litmus blue and forms dense white fumes with hydrogen chloride gas.

Inference; NH³ from NH⁴+.

(2biii)

Test; 2cm³ of filtrate + BaCl² + excess HCl.

Observation; white precipitate, precipitate remains.

Inference; SO²- CO3²- or SO4²- is present, SO4²- confirmed.

(2ci)

Test; Residue + HNOg.

Observations; effervescence of a colourless and odourless gas, which turns like water milky and turns moist blue to litmus red.

Inference; CO2 from CO3²-

(2cii)

Test; 2ci + NH3 in drops in excess

Observations; blue precipitate. Precipitate dissolved to give a deep blue solution.

Inference; CU2+ present.

CU2+ confirmed.

(3ai)

The value will increase.

(3aii)

The occur as a result of the decrease in the concentration of base due to the added volume of water.

(3bi)

There will be no visible reaction because copper is less than Zinc in the electrochemical series.

(3bii)

It absorbs water and become sticky because it is hygroscopic.

(3biii)

The solution turns pink.

(3c)

When NaOH is added to the solution of zn³+, a white precipitate is formed which later dissolve in excess NaOH due to the formation of zinc hydroxide

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