WAEC Past Questions and Answers - Page 1285

6,421.

Why are \(H_2SO_4\) and \(CaCl_2\), not suitable for drying ammonia gas? They

A.

are poisonous.

B.

pollute the gas

C.

are corrosive

D.

react with the gas

Correct answer is D

\(H_2SO_4\) and \(CaCl_2\) are not suitable for drying ammonia gas because they react with the gas.

Ammonia is a basic gas, and both \(H_2SO_4\) and \(CaCl_2\) are acidic. When these two substances react, they form salts that contain ammonia. This can contaminate the ammonia gas and make it unusable.

In addition, \(H_2SO_4\) is a corrosive substance, and \(CaCl_2\) can be harmful to breathe in. Therefore, it is not safe to use these substances to dry ammonia gas.

6,422.

The reduction half equation of the following reaction is:
\(Zn_{(s)} + CuSO_{4(aq)} → ZnSO_{4(aq)} + Cu_{(s)}\)

A.

\(Zn_{(s)} → Zn^{2+}_{(aq)} + 2e^-\)

B.

\(CuSO_{4(s)} + H_2O_{(l)}\) → \(Cu^{2+}_{(aq)}\) + \(SO_{4(aq)}^{2-}\)

C.

\(Cu^{2+}_{(aq)} + 2e^- → Cu_{(s)}\)

D.

\(Cu^{2+}_{(aq)} + e^- → Cu_{(s)}\)

Correct answer is C

The reduction half equation for the given reaction is:

\(Cu^{2+}_{(aq)} + 2e^- → Cu_{(s)}\)

In the overall reaction, copper(II) ions (\(Cu^{2+})\) gain two electrons (2e^-) and get reduced to form solid copper (Cu) metal. This is the reduction half-reaction in the redox reaction between zinc (Zn) and copper(II) sulfate (\(CuSO_4)\).

6,423.

The molecule that has a non-polar covalent bond is

A.

HCl

B.

\(NH_3\)

C.

\(Cl_2\)

D.

\(H_2O\)

Correct answer is C

In \(Cl_2\), the two chlorine atoms are identical and have the same electronegativity. Since both atoms have the same electronegativity, the electrons in the covalent bond are shared equally, resulting in a non-polar covalent bond. The molecule does not have a significant separation of charge and lacks a permanent dipole moment

6,424.

Petrochemistry is an example of

A.

applied chemistry

B.

Biochemistry

C.

Pure chemistry

D.

Environmental chemistry

Correct answer is A

Applied chemistry refers to the practical application of chemical principles and techniques to solve real-world problems and create useful products. Petrochemistry is a branch of applied chemistry that deals specifically with the chemical processes and transformations involved in the extraction, refining, and processing of petroleum and its derivatives

6,425.

Which of the following elements has its valence electrons in the s-orbital?

A.

Aluminum

B.

Phosphorus

C.

Sodium

D.

Carbon

Correct answer is C

Sodium is an alkali metal, and its atomic number is 11. This means that it has 11 electrons, and its electron configuration is \(1s^2 2s^2 2p^6 3s^1\). The valence electrons are the electrons in the outermost shell, which in this case is the 3s orbital.