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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.

106.

What is the product of the electrolysis of aqueous sodium chloride (NaCl) using inert electrodes?

A.

Hydrogen gas at the cathode and chlorine gas at the anode

B.

Hydrogen gas at the cathode and oxygen gas at the anode

C.

Sodium metal at the cathode and chlorine gas at the anode

D.

Sodium metal at the cathode and oxygen gas at the anode

Correct answer is B

During the electrolysis of aqueous sodium chloride using inert electrodes (such as platinum or carbon), the cations (H+) are attracted to the cathode and are reduced to form hydrogen gas (H2). The anions (OH) are attracted to the anode and are oxidized to form oxygen gas (O2).

107.

Which of the following alkanes has a straight-chain structure?

A.

Cyclopentane (C5H10)

B.

Isobutane (C4H10)

C.

2 - methyl propane (C4H10)

D.

Pentane (C5H12)

Correct answer is D

Pentane (C5H12) is a straight-chain alkane. Alkanes are hydrocarbons with the general formula CnH2n+2. They are called straight-chain alkanes if all the carbon atoms are connected in a continuous chain without any branches. Butane and Isobutane are both C4H10, but Isobutane has a branched structure, not a straight chain. Cyclopentane (C5H10) is a cycloalkane, not a straight-chain alkane.

108.

Which type of chemical combination involves the transfer of electrons from one atom to another, resulting in the formation of oppositely charged ions?

A.

Ionic bonding

B.

Hydrogen bonding

C.

Covalent bonding

D.

Metallic bonding

Correct answer is A

Ionic bonding occurs between a metal and a non-metal. The metal atom donates one or more electrons to the non-metal atom, resulting in the formation of positively charged cations and negatively charged anions. These oppositely charged ions are held together by electrostatic forces to form an ionic compound.

109.

What is the trend for ionization energy across a period in the periodic table?

A.

Increases from left to right.

B.

Remains constant

C.

Varies randomly

D.

Decreases from left to right

Correct answer is A

Ionization energy generally increases from left to right across a period. Ionization energy is the energy required to remove an electron from a neutral atom, and as you move from left to right, the atomic size decreases, making it harder to remove an electron, and thus, the ionization energy increases.

110.

Balance the following redox reaction:
Fe2O3 + CO → Fe + CO2

A.

Fe2O3 + CO → 2Fe + 2CO2

B.

2Fe2O3 + 3CO → 4Fe + 3CO2

C.

Fe2O3 + 2CO → 2Fe + 2CO2

D.

Fe2O3 + 3CO → 2Fe + 3CO2

Correct answer is D

To balance the redox reaction, we need to ensure that the number of atoms of each element and the total charge are the same on both sides of the equation. In this reaction, we can see that the number of oxygen (O) atoms is not balanced. To balance them, we need to add a coefficient of 3 in front of CO2 to get 3CO2. Similarly, the number of iron (Fe) atoms is not balanced. To balance them, we need to add a coefficient of 2 in front of Fe to get 2Fe