Chemistry questions and answers

Chemistry Questions and Answers

Learn more about the properties, composition, and structure of substances (elements and compounds) with these Chemistry questions and answers. This Test can be used by students preparing for Chemistry in JAMB, WAEC, NECO or Post UTME.

116.

Which of the following methods can be used to remove temporary hardness from water?

A.

Boiling

B.

Filtration

C.

sedimentation

D.

Chlorination

Correct answer is A

Temporary hardness in water can be removed by boiling. When water is boiled, the calcium and magnesium bicarbonates decompose, forming insoluble calcium carbonate (CaCO3) and magnesium carbonate (MgCO3), which precipitate out of the water.

117.

Which trace gas in the atmosphere plays a significant role in the greenhouse effect?

A.

Oxygen

B.

Argon

C.

Carbon dioxide

D.

Nitrogen

Correct answer is C

Carbon dioxide (CO2) is a trace gas in the atmosphere, but it plays a significant role in the greenhouse effect. It absorbs and traps heat from the Earth's surface, contributing to global warming.

118.

What is the solubility product constant (Ksp) used for?

A.

To measure the total mass of a solute that can dissolve in a solvent

B.

To determine the concentration of a solute in a saturated solution

C.

To calculate the solubility of a solute in a given solvent

D.

To compare the solubilities of different solutes in the same solvent

Correct answer is B

The solubility product constant (Ksp) is a constant specific to a given solute and solvent at a particular temperature. It is used to calculate the concentration of a solute in a saturated solution, where no more solute can dissolve at equilibrium.

119.

What is the chemical structure of soap and detergent molecules?

A.

Hydrophilic head and hydrophobic tail

B.

Hydrophilic head and hydrophilic tail

C.

Hydrophobic head and hydrophobic tail

D.

Hydrophilic tail and hydrophobic head

Correct answer is A

Both soap and detergent molecules have a hydrophilic (water-attracting) head and a hydrophobic (water-repelling) tail. The hydrophilic head allows the molecules to interact with water, while the hydrophobic tail interacts with oils and grease.

120.

What happens to the value of the equilibrium constant (Kc) for a reaction if the reaction is reversed?

A.

It becomes zero

B.

It becomes negative

C.

It remains the same

D.

It becomes the reciprocal of the original value

Correct answer is D

If a reaction is reversed, the equilibrium constant (Kc) for the reversed reaction becomes the reciprocal of the original equilibrium constant. For a reaction:
A + B ⇌ C + D
The equilibrium constant Kc = [C][D]/[A][B]
For the reversed reaction:
C + D ⇌ A + B
The equilibrium constant Kc(reversed) = [A][B]/[C][D]
Thus, Kc(reversed) = 1/Kc.