JAMB Chemistry Past Questions & Answers - Page 414

2,066.

An elements X with relative atomic mass 16.2 contains two isotopes 168X with relative abundance of 90% and m8X with relative abundance of 10%. The value of m is

A.

16

B.

18

C.

12

D.

14

Correct answer is B

168X, m8X
16 * (90/100) + m * (10/100) = 16.2
1440 + 10m = 1620
10m = 180
m = 18

2,067.
2,068.

Millikan's contributions to the development of atomic theory is the determination of

A.

charge on electron

B.

positive rays

C.

charge to mass ratio

D.

cathode rays

Correct answer is A

No explanation has been provided for this answer.

2,069.

An oxide XO2 has a vapour density of 32. What is the atomic mass of X?

A.

32

B.

20

C.

14

D.

12

Correct answer is A

Relative molecular mass of XO2 =2 × vapour density

Relative molecular mass → 32 * 2 = 64
Atomic mass of X:

X + [16 * 2] = 64
X = 64 - 32
=32

2,070.

Cancerous growths are cured by exposure to

A.

γ - rays

B.

β - rays

C.

α - rays

D.

infrared rays

Correct answer is A

No explanation has been provided for this answer.