Chemistry Past Questions and Answers

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:

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:

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:

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:

3. 06 g of a sample of potassium trioxochlorate (V) (KCIO) was required to make a saturated solution with 10cm3 of water at 25oC. The solubility of the salt at 25oC 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