Enlighten knowledge exam, Chemistry trial for 2023 WAEC candidates.

OBJECTIVE TEST.

1. The difference in energy between the reactants and the activated complex is known as…….

A. enthalpy change B. activation energy

C. activated complex D. intermediate

2. Breaking of crystals into gaseous ions during the dissolution of ionic solids requires energy input called……………….

A. hydration energy B. ionization energy

C. atomization energy D. lattice energy

3. The scientific method is a process that involves following certain steps. Which of these steps would come first?

A. make a hypothesis B. identify the problem

C. conduct an experiment D. do analysis of data gathered

4. At 28°C and 740mmHg. 1.0 dm3 of an unidentified gas has a mass of 5.16 g. What is the molar mass of the gas? [ R = 0.0821 dm3.atm.mol-1K-1 ]

A. 132 g/mol B. 84 g/mol

C. 130.9 g/mol D. 100 g/mol

5. An oxide of nitrogen contains 63.6% of nitrogen. What is the empirical formula of the compound?

A. NO B. NO2

C. N2O D. N2O3

6. Which is the correct order of increasing boiling point among the following molecules?

A. SiH4, CH4, NH3, H2O B. CH4, SiH4, NH3, H2O

C. CH4, SiH4, H2O, NH3 D. H2O, NH3, SiH4, CH4

7. ……… is not an alkaline earth metal

A. Cs B. Mg C. Ca D. Sr

8. In the mass spectrometer, deflection of ions by the magnetic field depend upon the

A. mass of the ion B. ratio of mass to charge of the ion

C. chemical nature of the ion D. size of the ion

9. In metallic solids, the forces of attraction are between the mobile valence electrons and the

A. sea of delocalized electrons B. fixed negative ions

C. positively charged nuclei D. neutrons

10. The unit of rate constant, k, for a fourth order reaction is…………………………..

A. mol-2dm6s-1 B. mol-3dm6s-1

C. mol-3dm9s-1 D. mol-4dm9s-1

11. Which of the following organic compounds can undergo both addition and substitution reactions?

A. Pentane B. Benzene

C. Propane D. Hexane

12. What is the solubility of a salt if 0.4g of it is obtained on evaporating 200cm3 of its saturated solution to dryness?

A. 0.08gdm−3 B. 2.00gdm−3

C. 8.00gdm−3 D. 80.00gdm−3

13. Consider the following reaction equation: Br2+2KI→2KBr+I2. Bromine is acting as

A. an oxidizing agent B. a reducing agent

C. an acid D. a base

14. When a salt is added to its saturated solution, the salt

A. dissolves and the solution becomes super saturated

B. dissolves and the solution becomes unsaturated

C. precipitates and the solution remains unchanged

D. dissolves and crystals are formed

15. Stainless steel is an alloy comprising of

A. Fe and C B. Fe and Ni

C. Fe, C and Ni D. Fe, C and Al

16. The position of equilibrium in a reversible reaction is affected by

A. particle size of the reactants

B. vigorous stirring of the reaction mixture

C. presence of a catalyst

D. change in concentration of the reactants

17. One of the criteria for confirming the purity of benzene is to determine its

A. heat capacity B. boiling point

C. mass D. colour

18. The empirical formula of a compound containing 0.067mol Cu and 0.066mol O is [Cu=63.5, O = 16]

A. Cu2O B. CuO C. CuO2 D. CuO4

19. The law of definite proportions states that

A. pure samples of the same compound contain the same elements combined in the same proportion by mass

B. pure samples of substances are in the same proportion by mass

C. chemical compounds are pure because they contain the same elements

D. matter can neither be created nor destroyed.

20. The atomic number of an isotope of hydrogen is equal to its mass number because it

A. has a totally filled valence shell

B. has a high charge to mass ratio

C. does not contain neutrons

D. exhibits isotopy

21. Particles in a solid exhibit

A. vibrational motion

B. vibrational and translational motion

C. vibrational and random motion

D. random and translational motion

22. The mass of potassium hydroxide required to make 300.ocm3 of 0.4 moldm-3 solution is {KOH = 56.0}

A. 26.88g B. 13.44g C. 6.72g D. 3.36g

23. Metals can be stretched into wires because they are

A. Ductile B. Good conductors

C. Lustrous D. Malleable

24. Aluminum is used in the manufacture or aircraft because it

A. Is hard and brittle

B. Is light and resists corrosion

C. Has high density and conducts electricity

D. Is malleable and ductile

25. An unsaturated solution differs from a saturated solution at a given temperature because it

A. Cannot dissolve more solute

B. Can hold more solute than it can actually dissolve

C. Can still dissolve more solute at given temperature

D. Form crystal more easily on cooling

26. The shape of the water molecule is_______?

A. Linear B. Pyramidal

C. Tetrahedral D. V-shaped

27. The minimum amount of energy required for effective collisions between reacting particles is known as

A. Activation energy B. Bond energy

C. Kinetic energy D. Potential energy

28. Which of the following apparatus can be used to measure a specific volume of a liquid accurately?

A. Beaker B. Conical flask

C. Measuring cylinder D. Pipette

29. Chlorine water is used as a bleaching agent because it is

A. An acidic solution B. An alkaline solution.

C. An oxidizing agent D. A reducing agent

30. When a compound X is heated with concentrated tetraoxosulphate (VI) acid, it produces an alkene. X is an

A. Alkane B. Alkanol

C. Alkanoate D. Alkyne

SUBJECTIVE TEST

1. Explain briefly each of the following terms:

rate law;
overall order of reaction
activation energy
effective collisions

2. Mention four factors that may affect the rate of chemical reactions.

3. Using both the collision and activation energy theories, explain how temperature affects the rate of chemical reactions.

4. A solution S contains 15.9 g of sodium carbonate in 1 dm3 of solution. Find its

mass density
molarity

5. State Hess’s law of constant heat summation.

ANSWER TO OBJECTIVE TEST

B. activation energy
D. lattice energy
B. identify the problem
C. 130.9 g/mol
D. N2O3
D. H2O, NH3, SiH4, CH4
A. Cs
B. ratio of mass to charge of the ion
C. positively charged nuclei
C. mol-3dm9s-1
B. Benzene
B. 2.00gdm−3
A. an oxidizing agent
C. precipitates and the solution remains unchanged
C. Fe, C and Ni
D. change in concentration of the reactants
B. boiling point
B. CuO
A. pure samples of the same compound contain the same elements combined in the same proportion by mass
C. does not contain neutrons
A. vibrational motion
C. 6.72g
A. Ductile
B. Is light and resists corrosion
C. Can still dissolve more solute at given temperature
D. V-shaped
A. Activation energy
D. Pipette
C. An oxidizing agent
B. Alkanol