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.

3,711.

Which of the following statement is correct about the periodic table?

A.

Elements in the same period have the same number of valency electron

B.

The valence electron of the elements in the same period increase progressively across the period

C.

Elements in the same group have the same number of electron shells

D.

The non-metallic properties of the elements tend to decrease across each period

Correct answer is B

The valence electron of the elements in the same period increase progressively across the period due to an increase in atomic number

3,712.

The fundamental difference between the three states of matter is the

A.

shape of their particles

B.

number of particles in each state

C.

shape of the container they occupy

D.

degree of movement of their particles

Correct answer is D

the fundamental difference between the three states of matter is their degree of movement, gaseous particles are very loosely packed hence they can move about easily. The particles of solids are closely packed so solids only make vibrational movement, while liquid particles can move past each other because their particles are not as closely packed as those of solids. 

3,713.

The partial pressure of oxygen in a sample of air is 452 mm Hg and the total pressure is 780 mm Hg. What is the mole fraction of oxygen?

A.

0.203

B.

0.579

C.

2.030

D.

5.790

Correct answer is B

Mole fraction = \(\frac{\text{Partial pressure of component}}{\text{Total pressure of compound}}\)

= \(\frac{452}{780}\)

= 0.579

3,714.

The ratio of the initial to final pressure of a given mass of gas is 1:1.5. Calculate the final volume of the gas if the initial volume was 300 cm3 at the same temperature

A.

120 cm3

B.

200 cm3

C.

450 cm3

D.

750 cm3

Correct answer is B

From P1V1 = P2V2
1 * V1 = 1.5 * V2
((1 * 300)/1.5) = V2
∴ V2 = 200 cm3

3,715.

How many moles HCL will be required to react with potassium heptaoxodichromate (VI) to produce 3 moles of chlorine?

A.

14

B.

12

C.

11

D.

10

Correct answer is A

K\(_{2}\)Cr\(_{2}\)O\(_{7}\) + HCl  → Cl\(_{2}\) + KCl + CrCl\(_{3}\) + H\(_{2}\)O

Balancing the equation, we have

K\(_{2}\)Cr\(_{2}\)O\(_{7}\) + 14HCl → 3Cl\(_{2}\) + 2KCl + 2CrCl\(_{3}\) + 7H\(_{2}\)O