JAMB Chemistry Past Questions & Answers - Page 95

471.

Which of the following derivatives of nitrogen affords an aqueous solution having a pH of less that 7?

A.

N2O

B.

NO

C.

NO2

D.

NaNO3

E.

NH3

Correct answer is C

No explanation has been provided for this answer.

472.

When copper (ii) sulphate solution is treated with excess ammonium hydroxide, a precipitate is first formed, and then this dissolves to give a deep blue solution.

This deep blue solution is a?

A.

Cu(OH)2

B.

CuSo4.5H2O

C.

(NH4)2SO4

D.

Cu(NH3)4(OH)2

E.

CuSO4.(NH4)2SO4.2H2O

Correct answer is D

\(CuSO_4+2NH_4OH→(NH_4)_2SO_4+Cu(OH)_2\)(pale−blue)

The pale blue precipitate of copper hydroxide dissolves in excess of ammonium hydroxide forming tetraamine copper [II] sulphate, an azure blue(deep blue) soluble complex salt.

\(Cu(OH)_2+(NH_4)_2SO_4+2NH_4OH→[Cu(NH_3)_4]SO_4+4H_2O\)

473.

Which of the following tests would confirm-unequivocally that a solution X contain the sulphate ion if it gives with?

A.

silver nitrates solution, a white precipates insoluble in dilute HNO3

B.

barium chloride solution, a white precipitate insoluble in dilute H2SO4

C.

barium chloride solution, a white precipitate soluble in dilute HCl

D.

barium chloride solution a white precipitate soluble in dilute ammonia

E.

barium chloride solution a white precipitate insoluble in dilute HCl

Correct answer is E

Sulfate ions in solution are detected using barium chloride solution.

The test solution is acidified using a few drops of dilute hydrochloric acid, and then a few drops of barium chloride solution are added.

A white precipitate of barium sulfate forms if sulfate ions are present.

475.

Which of the following represents a precipitation reaction?

A.

H2SO4 + NaCl \(\to\) NaHSO4 + HCl

B.

Fe +H2SO4 \(\to\) FeSO4 + H2

C.

4HCl + MnO2 \(\to\) MnCl2 + 2H2O + Cl2

D.

Na2SO4 + pb(NO3) \(\to\) PbSO4 + 2NaNO

E.

CuO +2HCl \(\to\) Cl2 + H2O

Correct answer is D

No explanation has been provided for this answer.