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.

931.

An organic compound contains 72% carbon, 12% hydrogen and 16% oxygen by mass. The empirical formula of the compound is

A.

C8H22O3

B.

C6H10O3

C.

C12H12O

D.

C6H12O

E.

C3H6O

Correct answer is D

carbon = 72%, hydrogen = 12%, 16%

Dividing by the atomic weight we have for C = \(\frac{5}{1}\) = 6

H = \(\frac{12}{1}\) = 12

O = \(\frac{16}{16}\) = 1

Divide by the smallest number, we have = \(\frac{6}{1}\) = 6

H = \(\frac{12}{1}\) = 12

O = \(\frac{1}{1}\) = 1

The formula is C6H12O

932.

Which of the following conduct electricity?

A.

sulfur

B.

graphite

C.

diamond

D.

red phosphorus

E.

yellow phosphorus

Correct answer is B

No explanation has been provided for this answer.

933.

When 50cm3 of a saturated solution of sugar (molar mass 342.0g) at 40oC was evaporated to dryness, 34.2g of dry solid was obtained. The solubility of sugar at 40oC is

A.

10.0 moles dm-3

B.

7.0 moles dm-3

C.

3.5 moles dm-3

D.

2.0 moles dm-3

Correct answer is D

No explanation has been provided for this answer.

934.

Which of the following groups of physical properties increases from left to right of the periodic table?

i. Ionization energy ii. Atomic radius iii. Electronegativity iv. Electron affinity

A.

i and ii

B.

i, ii and iii

C.

iii and iv

D.

i, iii and iv

Correct answer is D

Atomic radius is the distance from the atom's nucleus to the outer edge of the electron cloud. In general, atomic radius decreases across a period and increases down a group. 

935.

An element with atomic number twelve is likely to be

A.

electrovalent with a velocity of 1

B.

electrovalent with a valency of 2

C.

covalent with a valency of 2

D.

covalent with valency of 4

Correct answer is B

No explanation has been provided for this answer.