Jamb Chemistry Past Questions and Answers

Question 336:

• JAMB 1983

In the preparation of some pure crystals of Cu (NO₃)₂ starting with CuO, a student gave the following statements as steps he employed. Which of these shows a flaw in his report ?

A. Some CuO was reacted with excess dilute H₂SO₄
B. The solution was concentrated
C. When the concentrate was cooled, crystals formed were removed by filtration
D. The crystals were washed with very little cold water
E. The crystals were then allowed to dry

Question 337:

• JAMB 1983

Which of the following separation processes is most likely to yield high quality ethanol (>95%) from palm wine?

A. Fractional distillation without a dehydrant
B. Simple distillation with a dehydrant
C. Fractional distillation with a dehydrant
D. Column chromatography
E. Evaporation

Question 338:

• JAMB 1983

Increasing the pressure of a gas

A. Lowers the average kinetic energy of the molecules
B. Decreases the density of the gas
C. Decreases the temperature of the gas
D. Increases the density of the gas
E. Increases the volume of the gas

Question 339:

• 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 340:

• JAMB 1983

3. 06 g of a sample of potassium trioxochlorate (V) (KCIO) was required to make a saturated solution with 10cm³ of water at 25^oC. The solubility of the salt at 25^oC is [K =39, Cl = 35.5, O = 16]

A. 5.0 moles dm³
B. 3.0 moles dm³
C. 2.5 moles dm³
D. 1.0 molesv
E. 0.5 moles dm³