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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.

551.

Atomic orbital is

A.

the circular path through which electrons revolve round the nucleus

B.

a region around the nucleus where electrons are most likely to be found

C.

the path around the nucleus through which electrons move

D.

the path around the nucleus through which protons move

Correct answer is B

The orbital is a path or region around the nucleus. The electrons move in the orbitals and not through it.

552.

The mass of one mole of (NH4)2CO3 is   [O=16.0, N=14.0, C=12.0, H=1.0]

A.

66.0g

B.

76.0g

C.

80.0g

D.

96.0g

Correct answer is D

This is same as asking for the molar mass of the compound

= (2×14.0)+(8×1.0)+12.0+(16.0×3)

= 28.0+8.0+12.0+48.0 = 96.0g

553.

The purity of a solid sample can best be determined by its

A.

boiling point

B.

melting point

C.

conductivity

D.

solubility

Correct answer is B

The purity of a solid can be determined by measuring the melting point. A pure solid will have a single, sharp melting point.

554.

The seperation of Nitrogen from oxygen using fractional distillation of air is possible because

A.

nitrogen is less dense than oxygen

B.

oxygen is more reactive than nitrogen

C.

of the difference in their boiling points

D.

they belong to the same period

Correct answer is C

The various gases vaporize as their boiling points are reached, then they are pumped away and separately re-liquefied for convenient storage.

555.

The species with no electron in the 3d-orbital is

A.

Zn2+

B.

Sc3+

C.

Cu

D.

Mn

Correct answer is B

Scandium has electronic configuration 1s22s22p63s23p63d14s2 hence, Sc3+ has configuration 1s22s22p63s23p6. Hence, no electron in the 3d-orbital.