JAMB Chemistry Past Questions & Answers - Page 28

136.

The reactions involving simultaneous oxidation and reduction?

A.

Automatic reactions

B.

Alternate reactions

C.

Reduction agency

D.

Redox reactions

Correct answer is D

Redox (reduction/oxidation) describes all chemical reactions in which atoms have an increase or decrease in oxidation number (oxidation state).

137.

A chemical process in which there is a gain of electrons is known as?

A.

Sublimation

B.

Reduction

C.

Oxidation

D.

Distillation

Correct answer is B

Reduction, any of a class of chemical reactions in which the number of electrons associated with an atom or a group of atoms is increased.

138.

An element having the atomic number 17 will resemble which of the following elements having atomic number as given below?

A.

33

B.

35

C.

18

D.

19

Correct answer is B

The Group 7 elements are called the halogens. They are placed in the vertical column, second from the right, in the periodic table . 

Chlorine (17), bromine(35) and iodine(53) are the first three of the Group 7 elements.

139.

The only metal that is anti-bacterial is?

A.

Iron

B.

Sodium

C.

Alluminium

D.

Copper

Correct answer is D

Aluminium sulfate is a salt soluble in water and is mainly used as a coagulating agent in the purification of drinking water.

Copper demonstrated the greatest antimicrobial activity. The silver coatings demonstrated the second most antimicrobial surface.

140.

A solution contains 20g of solute in 180g of solvent. If the solvent is water, what is the concentration of the solution in terms of mass by mass percentage

A.

11.%

B.

22.2%

C.

10%

D.

20%

Correct answer is C

Mass of Solution = Mass of Solute + Mass of Solvent → 20g + 180g

: Mass of Solution = 200g

Mass Percent = \(\frac{Mass of Solute}{Mass of Solution} * 100%\)

Mass percent = \(\frac{20}{200} * 100%\)

Mass percent = 10%