JAMB Past Questions and Answers - Page 1558

7,786.

2H2O (l) + 2F2(g) → 4HF(aq) + O2(g).
In the reaction above, the substance that is being reduced is

A.

O2(g)

B.

H2O(l)

C.

F2(g)

D.

HF(aq)

Correct answer is C

F(2) + 2e \(\rightarrow\) 2F- x 2

2F2 + 4e \(\rightarrow\) 4F-

7,787.

An insoluble salt can be prepared by

A.

the reaction of trioxocarbonate (V) with an acid

B.

double decomposition

C.

the action of dilute acid on an insoluble base

D.

the reaction of metals with an acid

Correct answer is B

No explanation has been provided for this answer.

7,788.

Which of the following substances is not a salt?

A.

Aluminium oxide

B.

Sodium hydrogentrioxosulphate (V)

C.

Sodium trioxocarbonate (V

D.

Zinc chloride

Correct answer is A

No explanation has been provided for this answer.

7,789.

Three drops of a 1.0 mol dm-3 solution of HCl was added to 20 cm3 of a solution of pH6.4. The pH of the resulting solution will be

A.

close to that of pure water

B.

less than 6.4

C.

greater than 6.4

D.

unaltered

Correct answer is B

No explanation has been provided for this answer.

7,790.

10.0 dm3 of water was added to 2.0 mol dm-3 of 2.5dm3 solution of HCl. What is the concentration of the final solution in mol dm-3?

A.

0.4

B.

8.0

C.

2.0

D.

0.5

Correct answer is A

C1V1 = C2V2

C2 = \(\frac{C_1V_1}{V_2}\)

= \(\frac{2.0 \times 2.5}{12.5}\)

= 0.4mol/dm-3