WAEC Chemistry Questions and Answers 2023/2024 – Objectives & Theory

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SEE ALSO: WAEC Biology Questions and Answers

WAEC Chemistry Objective Questions and Answers 2023

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Today’s Chemistry OBJ Answers

1-10: ABADCCBDCA

11-20: DCABCBBCCB

21-30: ADCADAABCA

31-40: CBBCCBCCBB

41-50: CACBCBADCA

(1a)
(i) An acid is any compound which, in a chemical reaction is able to attach itself to an unshared pair of electrons in another molecule-a base, to form a new compound.

(ii)
Alcl₃

(1b)
Salting out is the process of adding concentrated sodium chloride solution to soap, to decrease the solubility of the soap. It consequently separates out as a hard cake on the surface or cooling.

(1c)
Reagent: {Ammonical solution of Silver trioxonitrate(v) [AgNo₃]}
Condition: {At room temperature}

(1d)
The percentage abundance of an isotope is the percentage of all naturally occurring atoms with a specific atomic mass of an element.

(1e)
(i)The element with atomic number 18 has electronic configuration 2,8,8. It has a completely filled valence shell. It is therefore inert. Hence it cannot have an oxide.

(ii)Being a covalent compound, the intermolecular forces between the Cl₂O molecules are weak and easily overcome.

(1f)
Add barium chloride solution to H₂SO₄ and HNO₃ separately. A white precipitate is formed in H₂SO₄ and no such precipitation is formed in HNO₃.

(1g)
(i)The main difference is that electrochemical cell does not need any external current for operation whereas electrolytic cells need external current to operate.

(ii)Also, Oxidation occurs at the positive electrode and reduction at the cathode, in the electrolytic cell. While the reverse is the case in electrochemical cells.

(1h)
As we go down group 1 from top to bottom, it gets easier to remove the valence electron and form the positively charged cation. Hence group 1 elements increase in chemical reactivity as we go down the group

(1i)
Molecular formula is a chemical formula that gives the total number of atoms of each element in each molecule of a substance.

(1j)
(i)Ammonia, NH₃ will deviate more than hydrogen gas H₂

(ii)
-Ammonia have stronger intermolecular forces than H₂
-Ammonia has more volume than H₂ at the same concentration

NOTE: The questions below are sample, likely and past questions and answers on chemistry which helps you practice and understand how WASSCE chemistry questions are being set.

WAEC Chemistry Possible Questions and Answers 2023

1. What condition favours the formation of the product for the endothermic reaction, N2O4(g) —><—– 2NO2(g)

A. Decrease in pressure

B. A decrease in volume

C. An increase in pressure

D. A constant volume

ANSWER: A ( Decrease in pressure)

2. How many alkoxy alkanes can be obtained from the molecular formula C₄ H₄O₄

A. 1

B. 2

C. 3

D. 4

ANSWER: C (3)

3. Element Y has two isotopes Y and Y present in the ratio 1:3. The relative atomic mass of Y would be

A. 20.5

B. 21

C. 21.5

D. 22

ANSWER: C (21.5)

4. 100.0g of KClO₃ was added to 40.0 cm^3 of water to give a saturated solution at 298K. If the solubility of the salt is 20.0 moldm^-3 at 298K, what percentage of the salt is left undissolved? {K= 39, Cl = 35.5, O = 16}

A. 80%

B. 60%

C. 5%

D. 2%

5. Elements X and Y have electronic configuration 1S²2S²2P⁴ and 1S²2S²2P⁶3S²3P¹ respectively. When they combine the formula of the compound formed is

A. XY

B. Y₂X₃

C. Y₂ X₃

D. Y X₂

ANSWER: B (Y₂X₃)

6. A solution of 0.20 mole of NaBr and 0.20 mole of MgBr₂ in 2.0 dm³ of water is to be analysed. How many moles of Pb(NO₃ )₂ must be added to precipitate all the bromide as insoluble PbBr₂

A. 0.30 mol

B. 0.10 mol

C. 0.20 mol

D. 0.40 mol

ANSWER: A (0.30 mol)

7. Na₂CO₃ + HCl —-> NaHCO₃ + NaCl. The indicator most suitable for this reaction should have pH equal to.

A. 3

B. 5

C. 7

D. 9

ANSWER: D (9)

8. A satuarted solution of silver trioxocarbonate (IV), was found to have concentration of 1.30 x 10^-5 moldm^-3 . The solubility product of the trioxocarbonate (IV) is

A. 8.79 x 10^-15

B. 1.69 x 10^-10

C. 1.82 x 10^-11

D. 9.84 x 10^-10

ANSWER: A (8.79 x 10^-15)

9. When platinum electodes are used during the electrolysis of copper (II) tetraoxosulphate (IV) solution, the solution gets progressive

A. Acidic

 

B. Basic

C. Neutral

D. Atmospheric

ANSWER: A (Acidic)

10. Tetraoxosulphate (VI) ions are final test using

A. acidified silver nitrate

B. acidic barium chloride

C. lime water

D. dilute hydrochloric acid

ANSWER: D (dilute hydrochloric acid)

PAPER 2 (ESSAY)

SECTION A

1. Identify the solid remaining when each of the following is heated.
(a) lithium trioxonitrate (V)
(b) potassium trioxonitrate (V)
(c) calcium trioxonitrate (V)

2. (a) When calcium oxide and coke are heated in an electric furnace, the products are carbon (ii) oxide and calcium carbide (CaC2), write the equation for this reaction.

(b) The addition of water to calcium carbide leads to the formation of calcium hydroxide and ethyne. Write the equation for the production of ethyne.

3. Calculate the percentage by mass of silicon tetrachloride. [2 marks]
4. Ammonia, NH3, and phosphine, Ph3, are the hydrides of the first two elements in group 5.
(a) Draw a dot and cross diagram for the ammonia molecule. [2 marks]
(b) Sketch and explain the shape of the ammonia molecule. [3 marks]

5. The first ionization energy of chlorine is +1260KJmol-1.
(a) Define the term first ionization energy.
(b) State and explain the general trend in the values of the first ionization energy for the elements across the period, sodium to argon in the periodic table.

6. Compound A consisting of carbon and hydrogen only. The compound was found to contain 80% carbon by mass.
(a) Calculate the empirical formula of compound A using the data above.
(b) The relative molecular mass of compound A was found to be 30.
Use this information to deduce the molecular formula of compound A.
[H = 1.00 C = 12.00]

7. State two factors other than a change in temperature or the use of a catalyst that influence the rate of a chemical reaction.

Essay Chemistry Likely Questions and Answers 2023

SECTION B

1. (a) Two elements represented by the letters Q and R have atomic numbers 9 and 12 respectively.
(i) Write the election configuration of R.
(ii) To what group does Q belong in the periodic table.
(iii) Write the formula of the compound formed when Q combines with R.
(iv) Explain briefly, why Q is a good oxidizing agent.
(v) State whether R would be expected to form acidic or basic oxide.
(b) (i) State two assumptions of the kinetic theory of gases.
(ii) When some solids are heated, they change directly into the gaseous state. What name is given to this phenomenon?
(iii) List two substances which exhibit the phenomenon mentioned in (ii).
(iv) Write an expression to show the mathematical relationship between the rate of diffusion of a gas and its vapour.

2. An aqueous solution has a pH of 4.0.
(a) (i) What is the hydrogen ion concentration of the solution?
(ii) What effect will it have on litmus paper?
(iii) Which of the following salt solutions would have the same effect on litmus? Give a reason for your answer. NH4Cl(aq); NaCl(aq) ; CH3OON(aq).
(b) (i) Differentiate between a fine chemical and a heavy chemical.
(ii) Name two sources of air pollution.
(iii) Suggest one way of reducing air pollution in cities

3. (a) (i) Explain briefly the fermentation process.
(ii) Write a balanced equation for the fermentation of glucose.
(iii) What substance must be added to glucose solution to ferment it?
(iv) Explain briefly why tightly corked glass filled to the brim with palm wine shatters on standing.
(b) State one industrial application of each of the following methods of separation:
(i) Crystallization;
(ii) Fractional distillation.
(c) Explain the following terms:
(i) Saponification;
(ii) Esterification.
(d) Write a balanced equation to illustrate each of the terms in (c).
(e) i) What is hydrocarbon compound?
(ii) Name two principal sources of hydrocarbons.

SEE ALSO:

• WAEC Biology Practical Specimen PDF Download
• WAEC Maths Questions And Answers
• WAEC Physics Questions and Answers

Tips to Pass WAEC Chemistry Examination

The tips below will help you make success in all your WASSCE papers including physics.

Study your Books

This is the most important tip. If you must pass then you must read. Making success in WAEC is not by magic. It is by hard work. If you want to depend solemnly on expo then your chances of passing is slim.

Use Chemistry Past questions and answers

Past questions and answers have a lot to offer you which you may nit understand. In case you do not know, some questions and repeated from year to year but you won’t discover such until you have gone through them.

Past questions and answers also helps you understand how the whole questions would look like and what is expected of you.

Use Chemistry Syllabus and Recommended Textbooks

WAEC has mapped out areas of concentration for Chemistry which comprises of the WAEC approved topics, recommended textbooks and authors. It is meant to guide students towards making a greater success in their examinations. So, you are encouraged to download it online.