JAMB Chemistry Past Questions & Answers - Page 216

1,076.

What mass of a divalent metal M (atomic mass = 40) would react with excess hydrochloric acid to liberate 224cm^3 dry hydrogen gas measured at S.T.P?

A.

8.0 g

B.

4.0 g

C.

0.8 g

D.

0.4 g

Correct answer is D

let the divalent metal be Q

Q + 2HCl → QCl2 + H2

1mole of Q liberated 1 mole of Hydrogen gas ( one mole of any gas at STP has a volume of 22400cm^3 or 22.4dm^3 )

40  → 22400cm^3

? → 224cm^3

mass of Q = \(\frac{ 40 \times 224}{22400}\)

mass of Q = 0.4g.

1,077.

The movement of liquid molecules from the surface of the liquid to the gaseous phase above it is known as?

A.

Brownian movement

B.

condensation

C.

evaporation

D.

liquefaction

Correct answer is C

No explanation has been provided for this answer.

1,078.

An eruption pollution an environment with gas suspected to be H<sub>2</sub>S, a poisonous gas. A residue team should spray the environment with?

A.

water

B.

moist SO2

C.

acidified KMnO4 and water

D.

water, acidified KMnO4 and oxygen

Correct answer is B

No explanation has been provided for this answer.

1,079.

The molar ratio of oxygen to nitrogen in dissolved air is 2:1 whereas the ratio is 4:1 in atmospheric air because?

A.

nitrogen is less soluble than oxygen

B.

oxygen is heavier than nitrogen

C.

nitrogen has a higher partial pressure in air

D.

gases are hydrated in water

Correct answer is A

the ratio of oxygen to nitrogen in dissolved air is 2:1 whereas the ratio is 4:1 in atmospheric air. This is because oxygen in the air has a higher solubility than other elements in the air and also there is hydrogen bonding between water and oxygen that increases its solubility.

1,080.

The energy changes accompanying the addition of an electron to a gaseous atom is called?

A.

first ionization energy

B.

second ionization energy

C.

electron affinity

D.

electronegativity

Correct answer is C

No explanation has been provided for this answer.