JAMB Chemistry Past Questions & Answers

1,151.

An aqueous solution of an inorganic salt gave white precipitate (i) soluble in excess aqueous NaOH (ii) insoluble in excess aqueous NH3 (iii) with dilute HCl. The cation present in the inorganic salt is?

Na₄⁺

Ca⁺⁺

Zn⁺⁺

Al⁺⁺⁺

Pb₊₊

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Correct answer is E

No explanation has been provided for this answer.

1,152.

The process involved in the conversion of an oil into margarine is known as?

hydrogenation

condensation

pyrolysis

dehydration

cracking

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Correct answer is A

Margarine is an inexpensive alternate to butter, made from oil or a combination of oils through the process of hydrogenation.

1,153.

Addition of dilute hydrochloride acid to an aqueous solution of a crystalline salt yield a yellow precipitate and a gas which turned dichromate paper green. The crystalline salt was probably?

Na₂SO₄

Na₂S

Na₂S₂O₃.5H₂O

Na₂CO₃

NaHCO₃

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Correct answer is C

No explanation has been provided for this answer.

1,154.

When marble is heated to about 1473 K, another white solid is obtained which reacts vigorously with water to give an alkaline solution. The solution contains?

NaOH

KOH

Mg(OH)₂

Zn(OH)₂

Ca(OH)₂

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Correct answer is E

No explanation has been provided for this answer.

1,155.

The atomic number of an element whose cation, X2+, has the ground state electronic configuration 1s22s22p63s22p6 is?

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Correct answer is C

-The main difference between ground state and excited state is that ground state is a state where electrons in a system are in the lowest possible energy levels whereas excited state is any state of the system that has a higher energy than the ground state.

-Calcium atoms have 20 electrons and the shell structure is 2.8. 8.2. The ground state electron configuration of ground state gaseous neutral calcium is [Ar]