Water of crystallization - Jamb Chemistry Past Questions and Answers

Question 1:

• JAMB 1983

Sodium sulphate decahydrate (Na₂SO₄.10 H₂O) on exposure to air loses all its water of crystallization.
The process of loss is known as

A. Efflorescence
B. Hygroscopy
C. Deliquescence
D. Effervescence
E. Dehydration

Question 2:

• JAMB 1983

2.5 g of a hydrate barium salt gave on heating, 2.13 g of the anhydrous salt. Given that the relative molecular mass of the of the anhydrous salt is 208, the number of molecules of water of crystallization of the barium salt is

A. 10
B. 7
C. 5
D. 2
E. 1

Question 3:

• JAMB 1984

The solubility curves of four substances are shown in the figure above. Which of the four substances would crystallize from a saturated solution cooled from 353K(80^oC)to 323K(50[sup][/sup]C)?

A. P and Q
B. P and R
C. P and S
D. R and S
E. Q and R

Question 4:

• JAMB 1985

Addition of dilute hydrochloride acid to an aqueous solution of a crystalline salt yield a yellow precipitate and a gas which turned dichromate paper green. The crystalline salt was probably?

A. Na₂SO₄
B. Na₂S
C. Na₂S₂O₃.5H₂O
D. Na₂CO₃
E. NaHCO₃

Question 5:

• JAMB 1988

The forces holding naphthalene crystals together can be overcome when naphthalene is heated to a temperature of 354K resulting in the crystal to melting. These forces are known as?

A. Coulombic
B. Ionic
C. Covalent
D. Van der waals