Classroom

Chemistry Past Questions

Study and practice Chemistry past questions with answers and detailed explanations. Then test your knowledge using our interactive CBT practice platform and prepare confidently for your upcoming examinations.

1,623 questions JAMB 2505 WAEC 1623 NECO 168 CUSTOM 10

Select subject

Download PHP app Ask a Question Check Syllabus Past Question Videos Topic Video Lessons

Take a test

Custom CBT

Create and set up a CBT environment with your preferred subjects.

JAMB CBT Simulator

Practice JAMB CBT with real UTME past questions in CBT format.

WAEC CBT Practice 2026 Simulator

CB-WASSCE styled past question practice.

NECO CBT Practice 2026 Simulator

SSCE & GCE styled past question practice.

Past Questions

1,623 questions

Question 1 of 20 1,623 total questions

Question 771

waec 1990

How many molecules are there in 14g of nitrogen gas at s.t.p? (n = 14, Avogadro Number = 6. 0 x \(10^{23 }\)mol-1)

A1.2 x 10 ²³

B3.0 x 10²³

C6.0 x10²³

D1.2 x 10²⁴

E30 x10²³

View Explanation & Discuss

Question 772

waec 1990

A catayst which increases the rate of a chemical reaction does so by

Aincreasing the reaction pathway

Bincreasing the surface area of the reactants

Cincreasing the pressure on the system

Ddecreasing the temperature at which the reaction occurs

Edecreasing the activation energy of the reaction

View Explanation & Discuss

Question 773

waec 1990

Which of the following reactions does not occur in the blast furnace during the extraction of iron?

AFe₂O₃ _(s) + 3CO_(g) → 2Fe_(l) + 3CO₂_(g)

BC₂ + CO ₂_(g)

CCaO_(s) + SiO₂_(s) → CaSiO ₃_(s)

DFeO_(s) + CO₂_(g) + Fe_(l)

E2Fe₂O_(s) → 4Fe_(l) 3O₂_(g)

View Explanation & Discuss

Question 774

waec 1990

Which of the following compounds will undergo additional reactions?

AEthyne

BButane

CPentane

DTetrachloromethane

EEthanol

View Explanation & Discuss

Question 775

waec 1990

When a solid melts and consequently boils, there is

Aa gradual increase in the average kinetic energy of the particles

Ba sudden decrease in the kinetic energy of the particles

Cno change in the average kinetic energy of the particles

Da rapid change in the nature of bonding of the components

Ea change in the size of the fundamental particles

View Explanation & Discuss

Question 776

waec 1990

Aluminum is above iron in the electrochemical series, yet iron corrodes easily on exposure to air while aluminium does not. This is because aluminium

Ahas a lower density than iron

Bis a better conductor than iron

Cdoes not corrode spontaneously

Dforms thin layer of inert oxide in moist air

Eforms amphoteric oxides while iron does not

View Explanation & Discuss

Question 777

waec 1990

The heat accompanying the reaction represented by the equation H₂O _(l) → H ₂O_(g) is described as the heat of

Asolution

Bneutralization

Cvaporization

Dsublimation

Eactivation

View Explanation & Discuss

Question 778

waec 1990

The electronic configuration 1s^{2 2}2s ²2p ⁶3s²3p ⁶ is that of a

Anoble gas

BGroup ll element

CGroup lll element

DGroup V element

EGroup VI element

View Explanation & Discuss

Question 779

waec 1990

A sample of orange juice is suspected to have been contaminated with a yellow dye. Which of the following methods can be used to detect the dye?

ADecantation

BChromatography

CDistillation

DFiltration

EEvaporation

View Explanation & Discuss

Question 780

waec 1990

Which of the following reaction will not take place under normal conditions?

AZn_(s) + 2HCl → ZnCI_2(aq) + H _2(g)

BFe _(s) + H ₂SO_4(aq) → FeSO_4(aq) + H_2(g)

CCu _(s) + 2HCI _(aq) → CuCI _2(aq) + H_2(g)

DCa_(s) + 2H ₂O ₍₁₎ → Ca(OH)_2(g) + H_2(g)

E2Na_(s) + 2H ₂O ₍₁₎ → 2NaOH_(aq) + H_2(g)

View Explanation & Discuss

Question 781

waec 1990

Catalytic hydrogenation of oils results in the production of

Asoaps

Bdetergents

Calkanes

Dbutter

Emargarine

View Explanation & Discuss

Question 782

waec 1989

What is the voltage of the cell represented at Zn(s)/ Zn\(^{2+}\)(aq) //Cu\(^{2+}\)(aq) /Cu(s) given that for Cu\(^{2+}\)(aq)/ Cu (s) E\(^0\) = 0.337V and for Zn\(^{2+}\)(aq) /Zn(s)' E\(^0\) = - 0.763V?

A+0.426V

B-0.426V

C-0.337V

D-1.10V

E+1.10V

View Explanation & Discuss

Question 783

waec 1989

The oxidation number of chlorine is + 1 in

AKCIO ₃

BCI ₂O ₇

CZnCI₂

DHCI

ENaCIO

View Explanation & Discuss

Question 784

waec 1989

50cm\(^3\) of a saturated solution of potassium trioxonitrate (V)at 40°C contains 5.05g of the salt. What is the solubility of potassium trioxonitrate (V) at 40°C? (KNO\(_3\) = 101)

A1.0 mol dm^-3

B1.5 mol dm^-3

C2.0 mol dm^-3

D2.5mol dm^-3

E5.0mol dm^-3

View Explanation & Discuss

Question 785

waec 1989

Which of the following is a condition for a spontaneous reaction?

A∆H -T is zero

B∆H-T∆ S is positive

C∆H-T∆ S is negative

D∆S is zero

E∆S is positive

View Explanation & Discuss

Question 786

waec 1989

The electronic configuration of two atoms X and Y are as follows: X - 1s ² 2s ²2p ⁶3s ¹, Y -1s ²2s ²2p ⁶3s²3p ⁶4s ² which of the statements below is true of the position of X and Y in the Periodic Table?

Ax belongs to group 1, Y belongs to period 2,

Bx belongs to group 1, Y belongs to period 4

Cx belongs to group 2, Y belongs to period 1

Dx belongs to group 3, Y belongs to period 2

Ex belongs to group 3, Y belongs to period 4

View Explanation & Discuss

Question 787

waec 1989

What quantity of copper will be deposited by the same quantity of electricity that deposited 9.0g of aluminum? (A = 27, Cu = 64)

A64g

B32g

C7.1g

D6.4g

E3.2g

View Explanation & Discuss

Question 788

waec 1989

Which of the following statements is not true of tin? it

Ais a p-block element

Bis extracted from cassiterite SnO ₂

Cis used for protecting iron containers from corrosion

Dcombines with copper to form the alloy brass

Eshows two oxidation states, + 2 and + 4 in most of its compounds

View Explanation & Discuss

Question 789

waec 1989

The following are s-block elements except

Alithium

Bmagnesium

Cpotassium

Dcalcium

Ealuminium

View Explanation & Discuss

Question 790

waec 1989

Given that for the reaction. N2(g) + 3H2(g) ⇌ 2NH3(g) ∆H = -92kJ. What is the enthalpy of formation of ammonia from its elements?

A-46KJ mol ^-1

B-184KJmol ^-1

C-92KJmol ^-1

D184KJmol ^-1

E+46KJmol ^-1

View Explanation & Discuss

Question Navigator

Current

Chemistry Past Questions

Take a test

Custom CBT

JAMB CBT Simulator

WAEC CBT Practice 2026 Simulator

NECO CBT Practice 2026 Simulator

Past Questions

Question Navigator

MathsFaculty