JAMB Chemistry Past Questions & Answers - Page 403

2,011.

Three drops of a 1.0 mol dm-3 solution of NaOH are added to 20 cm3 of a solution of pH 8.4. The pH of the resulting solution will?

Close to that of pure water

Unaltered

Greater than 8.4

Less than 8.4

View answer & explanation

Correct answer is C

A strong base is one that fully dissociates to give ions in solution. Weak bases only partially dissociate in a solution,

while the strong bases dissociate fully in a solution. Weak bases have pH 7.3 – 10, strong ones have pH 10 – 14.

2,012.

When a salt loses its water of crystallization to the atmosphere on exposure, the process is said to be

Efflorescence

Deliquescence

Effervescence

Fluorescence

View answer & explanation

Correct answer is A

No explanation has been provided for this answer.

2,013.

Tetraoxosulphate (VI) acid burns the skin by

Hydrolysis

Hydration

Heating

Dehydration

View answer & explanation

Correct answer is D

No explanation has been provided for this answer.

2,014.

The solubility of a salt of molar mass 101g at 20^oC is 0.34 mol dm^-3. If 3.40g of the salt is dissolved completely in 250cm³ of water in a beaker, the resulting solution is

A suspension

Saturated

Unsaturated

Supersaturated

View answer & explanation

Correct answer is C

At 20^oC
0.34 mol/dm of the salt dissolve
= 0.34 * 101 = 34.34gm
Of the salt dissolved.
∴ 34.34gm dissolve is 1,000cm³
If only 250 cm³ is the required mass
X = (250/1000) * 34.34
= 8.555gm
If only 3.40gm of the salt dissolved ,the solution is unsaturated