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.

36.

The pair of compounds that belongs to the same homologous series is

A.

\(C_2H_6\) and \(C_4H_{10}\)

B.

\(C_3H_8\) and \(C_3H_6\)

C.

\(C_2H_4\) and \(C_4H_{10}\)

D.

\(C_4H_{10}\) and \(C_5H_{10}\)

Correct answer is A

In the given options, \(C_2H_6\) (ethane) and \(C_4H_{10}\) (butane) both belong to the same homologous series, as they have the same alkane functional group \(C_nH_{2n}+2\) and differ by a \(CH_2\) group:
\(C_2H_6\): Ethane
\(C_4H_{10}\): Butane
Both of these compounds are members of the alkane homologous series.

37.

Which of the following equimolar solutions has the highest conductivity?

A.

\(H_2SO{_4(aq)}\)

B.

\(NaOH{_(aq)}\)

C.

\(H_2CO{_3(aq)}\)

D.

\(CH_3COOH{_4(aq)}\)

Correct answer is A

\(H_2SO_4\)(aq) is a strong acid that dissociates into two hydrogen ions (H+) and one sulfate ion \(SO4^{2-}\) when dissolved in water. This leads to a higher concentration of ions in the solution, resulting in higher conductivity.

38.

How many moles are there in 3.0 g of \(O_2\)? [O = 16.0]

A.

0.0093 moles.

B.

0.0930 moles.

C.

0.0625 moles.

D.

0.6250 moles.

Correct answer is B

Number of moles = Mass / Molar mass
Given that the molar mass of oxygen \(O_2\) is 32.0 g/mol (2 × 16.0 g/mol), you can calculate the number of moles:
Number of moles = 3.0 g / 32.0 g/mol = 0.09375 moles
Rounded to four significant figures, the number of moles in 3.0 g of O2 is approximately 0.0938 moles.
Therefore, the closest answer choice is:
0.0930 moles.

39.

Species that occur in a reaction pathway but not in the overall reaction are known as

A.

Reactants

B.

Inhibitors

C.

Products

D.

Intermediates

Correct answer is D

In a chemical reaction, intermediates are the chemical species that are formed during the reaction but are subsequently consumed in further steps, leading to the final products. They are transient species that exist momentarily during the reaction process and are not present in the initial reactants or the final products of the overall reaction.

40.

A mixture containing two salts of different solubility can be separated by

A.

chromatography

B.

crystallization

C.

distillation

D.

evaporation

Correct answer is B

Crystallization is a separation technique that exploits differences in the solubilities of components in a solution. When a solution is allowed to cool or evaporate under controlled conditions, one of the salts may begin to crystallize out of the solution before the other due to its lower solubility. This process can be used to separate the salts based on their differing solubilities and crystal formation.


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