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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.

101.

What is the chemical formula of rust, which is formed on the surface of iron in the presence of oxygen and moisture?

A.

Fe3O4

B.

FeO

C.

Fe(OH)3

D.

Fe2O3

Correct answer is D

Rust is a reddish-brown compound that forms on the surface of iron in the presence of oxygen and moisture. Its chemical formula is Fe2O3, indicating the presence of two iron atoms and three oxygen atoms in the compound.

102.

What is the molar mass of water (H2O)?

A.

18 g/mol

B.

22 g/mol

C.

16 g/mol

D.

12 g/mol

Correct answer is A

The molar mass of water (H2O) is calculated by adding the atomic masses of its constituent elements: 2 hydrogen atoms (each with a molar mass of approximately 1 g/mol) and 1 oxygen atom (with a molar mass of approximately 16 g/mol). Therefore, the molar mass of water is 2 x 1 g/mol + 1 x 16 g/mol = 18 g/mol.

103.

Which organic compound is responsible for the characteristic aroma of fruits?

A.

Alkane

B.

Alkyne

C.

Ester

D.

Amine

Correct answer is C

Esters are organic compounds that have a pleasant, fruity aroma. They are responsible for the characteristic smells of fruits and many other fragrant substances.

104.

Which of the following factors does NOT affect the rate of a chemical reaction?

A.

Concentration of reactants

B.

Presence of a catalyst

C.

Molecular weight of products

D.

Temperature

Correct answer is C

The molecular weight of products is not directly related to the rate of a chemical reaction. The factors that affect the reaction rate include concentration of reactants, temperature, presence of catalysts, surface area, and the nature of the reactants and products.

105.

When an acidic solution is diluted, what happens to its pH?

A.

It depends on the specific acid

B.

It decreases

C.

It remains the same

D.

It increases

Correct answer is D

When an acidic solution is diluted by adding more solvent (usually water), the concentration of hydrogen ions (H+) decreases. As a result, the pH of the solution increases, making it less acidic