JAMB Chemistry Past Questions & Answers - Page 320

1,596.

How many grams of hydrogen gas will be liberated when 6g of magnesium ribbon dissolves in 500cm3 of 6M HCl?


(Mg=24, H=1, Cl=35.5)

A.

1.2 g

B.

0.7 g

C.

0.5 g

D.

0.3 g

E.

0.12 g

Correct answer is C

Mg + 2HCl → MgCl2 + H2
6 molar contains 6 Χ 36.5 gms 1000 cc

Solution i.e 6 Χ 36.5/2gms in 500 cc
= 3 Χ 36.5
24 gms of mg will react with 2 Χ 36.5 HCl to liberate 2 gm of hydrogen
∴ 6 gms will liberate 6 Χ 2/24 Χ 1 = 0.5 gm of H2

1,597.

Under high pressure, real gases do not obey gas laws because their molecules?

A.

have become more energetic

B.

have become less energetic

C.

have become smaller in size

D.

decompose into atoms

E.

start repelling each other

Correct answer is A

Van der Waals noticed the behavior of real gases at low temperature and high pressure possesses weak but short range forces.

1,598.

Which of the following reactions is correct as as written?

A.

FeCl2 + 3NH4OH → Fe(OH)3 + 3NH4Cl

B.

Pb2O3 + 4HCl → PbCl2 + 2H2O

C.

PbNO3 + H2S → PbS + 2HNO3

D.

NaOH + H2SO4 → NaHSO4 +H2O

E.

2NH4NO3 → N2 + 2H2O

Correct answer is D

No explanation has been provided for this answer.

1,600.

On heating, under suitable conditions, 1 litres of monoatomic gas,X, combines with 11/2 litres of an oxide, What is the formula of the oxide.

A.

XO3

B.

X2O3

C.

X3O2

D.

XO2

E.

None of the above

Correct answer is B

No explanation has been provided for this answer.