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.

41.

Which of the following statements is correct?

A.

Addition reactions occur between alkanes and chlorine.

B.

Butane has a lower boiling point than propane.

C.

Pentane has five isomers.

D.

An alkane with 49 carbon atoms contains 100 hydrogen atoms

Correct answer is D

The general formula for alkanes is \(C_nH_{2n}+2\). For an alkane with 49 carbon atoms (n = 49), the number of hydrogen atoms can be calculated as follows:

Number of hydrogen atoms (H) = 2n + 2
Number of hydrogen atoms (H) = 2 * 49 + 2
Number of hydrogen atoms (H) = 98 + 2
Number of hydrogen atoms (H) = 100

So, an alkane with 49 carbon atoms contains 100 hydrogen atoms.

42.

Dilute trioxonitrate (V) acid does not produce hydrogen when it reacts with metals because

A.

it reacts with the product.

B.

it is highly corrosive.

C.

there is no visible reaction.

D.

it is a strong oxidizing agent.

Correct answer is D

Dilute trioxonitrate (V) acid does not produce hydrogen when it reacts with metals because it is a strong oxidizing agent.
Trioxonitrate (V) acid, also known as nitric acid, is a strong oxidizing agent. This means that it can easily oxidize metals, which means that it can remove electrons from metals. When nitric acid oxidizes a metal, it forms salt and water. The salt does not contain hydrogen, so no hydrogen gas is produced

43.

Which of the following properties does not give evidence of the kinetic theory of matter?

A.

Diffusion

B.

Melting

C.

Polymerization

D.

Evaporation

Correct answer is C

Polymerization is a process in which small molecules combine to form larger molecules. This process is not consistent with the kinetic theory of matter because it does not involve the movement of particles. The particles in a polymer are not moving randomly. They are bonded together in a fixed structure.
Therefore, the property that does not give evidence of the kinetic theory of matter is polymerization.

44.

Which of the elements in the table below would react more readily with chlorine?
      

Element

Ionization energy (KJ \(mol^{-1} \times 10^{-3}\))

W 12.0
X 21.0
Y 106.0
Z 200.0

A.

Y and Z only

B.

X and Z only

C.

W and X only

D.

W and Z only

Correct answer is C

Among the given elements, W has the lowest ionization energy (\(12.0 KJ mol^{-1} x 10^{-3})\), indicating that it would be more likely to react with chlorine. X has a higher ionization energy \((21.0 KJ mol^{-1} x 10^{-3})\), so it would be less reactive with chlorine compared to W.
Based on ionization energy values, the elements that would react more readily with chlorine are W and X.

45.

The formation of a bond between hydrogen and a highly electronegative atom results in

A.

polarity

B.

electrovalent bond.

C.

dipole

D.

metallic bond

Correct answer is A

The formation of a bond between hydrogen and a highly electronegative atom results in polarity because the electronegative atom will attract the shared pair of electrons more than the hydrogen atom, creating a dipole with a partial negative charge on the electronegative atom and a partial positive charge on the hydrogen atom.

46.

Alkenes can be manufactured by

A.

the combustion of alkanes.

B.

the cracking of hydrocarbons.

C.

polymerization reactions.

D.

addition of hydrogen to unsaturated vegetable oils.

Correct answer is B

Cracking is a chemical process in which larger hydrocarbon molecules are broken down into smaller and more useful ones. This process is commonly used in petroleum refining to convert heavy hydrocarbons into lighter fractions, including alkenes. During cracking, high-temperature and/or catalytic conditions are applied to break the long carbon chains of hydrocarbons into shorter ones. This process produces a mixture of products, including alkenes, which are unsaturated hydrocarbons containing carbon-carbon double bonds.

47.

The following steps are scientific methods except

A.

experimentation

B.

problem identification

C.

Analysis

D.

Open-mindedness

Correct answer is D

From the given options, "Open-mindedness" is not a specific step in the scientific method. Open-mindedness is a general mindset that scientists should have throughout the entire process. It involves being receptive to new ideas, evidence, and interpretations, which helps scientists avoid biases and reach more accurate conclusions.

48.

Which of the following reactions represents the hydrolysis of an alkanoate?

A.

\(CH_3COOH + OH^- ⇌H^+⇌ CH_3COO^- + H_2O\)

B.

\(CH_3COOH + C_2H_5OH ⇌H^+⇌ CH_3COOC_2H_5 + H_2O\)

C.

\(CH_3COOC_2H_5 + H_2O ⇌H^+⇌ CH_3COO^- + CH_3CH_2OH\)

D.

\(CH_3COOCH_2CH_3 + H_2O ⇌H^+⇌ CH_3COOH + CH_3CH_2OH\)

Correct answer is D

The hydrolysis of an alkanoate is the reaction of an alkanoate with water to form a carboxylic acid and an alcohol. The correct reaction is:

\(CH_3COOC_2H_5 + H_2O ⇌H^+⇌ CH_3COOH + CH_3CH_2OH\)

49.

The following statements are correct except

A.

energy is released when liquids change to solids.

B.

carbon atoms in gaseous methane are further apart than those in solid diamond.

C.

there is large decrease in the volume of a solid metal when pressure is applied to it.

D.

particles move faster in the gaseous state than in the liquid state.

Correct answer is C

In general, solids are relatively incompressible compared to liquids and gases. When pressure is applied to a solid, there is typically only a small change in volume. Solids have tightly packed particles with strong intermolecular forces, making them less responsive to changes in pressure. Liquids and gases, on the other hand, can undergo larger volume changes in response to pressure.

50.

The vapour density of an organic compound with the molecular formula \(C_2H_4O_2\), is
[H=1.0, C=12.0, O= 16.0]

A.

40

B.

120

C.

65

D.

30

Correct answer is D

Molar mass of \(C_2H_4O_2\),= (12 × 2) + (1 × 4) + (16 × 2)= 60 g/mol
Vapour density = RMM/2
=60/2=30