JAMB Chemistry Past Questions & Answers - Page 268

1,336.

Oxygen is a mixture of two isotopes 16-O and 18-O with relative abundances of 90% and 10% respectively. The relative atomic mass of oxygen is?

A.

16.0

B.

16.2

C.

17.0

D.

18.0

Correct answer is B

816O, 818O
90% 10%
R.A.M = (90)/(100) x 16 + (10)/(100) x 18 = 14.4 + 1.8 = 16.2

1,337.

Two elements, P and Q with atomic numbers 11 and 8 respectively , combine chemically to form the compound PxQY. The respective values of x and y are?

A.

1 and 1

B.

1 and 2

C.

2 and 1

D.

3 and 1

Correct answer is C

No explanation has been provided for this answer.

1,338.

In the periodic table, what is the property that decreases along the periodic and increases down the group?

A.

Atomic number

B.

Electron affinity

C.

Ionization potential

D.

Atomic radius

Correct answer is D

No explanation has been provided for this answer.

1,339.

The electron configuration of two elements with similar chemical properties are represented by?

A.

1s22s22p5 and 1s22s22p4

B.

1s22s22p4 and 1s22s22p63s1

C.

1s22s22p63s1 and 1s22s1

D.

1s22s22p4 and 1s22s1

Correct answer is C

No explanation has been provided for this answer.

1,340.

The temperature of a body decreases when drops of liquid placed on it evaporate because?

A.

the atmospheric vapour pressure has a cooling effect on the body

B.

a temperature gradient exists between the drops of liquid and the body causing the latter to vaporate

C.

the heat of vapourization is drawn from the body causing it to cool

D.

the random motion of the liquid molecules causes a cooling effect on the body

Correct answer is C

No explanation has been provided for this answer.