Chemistry questions and answers

Chemistry Questions and Answers

Learn more about the properties, composition, and structure of substances (elements and compounds) with these Chemistry questions and answers. This Test can be used by students preparing for Chemistry in JAMB, WAEC, NECO or Post UTME.

2,301.

3. 06 g of a sample of potassium trioxochlorate (V) (KCIO\(_3\)) was required to make a saturated solution with 10cm\(^3\) of water at 25°C. The solubility of the salt at 25°C 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

Correct answer is C

Molar mass of KCIO\(_3\) = 122.5 g/mol

3.06g = 10
xg = 1000

\(frac{3.06 * 1000}{10}\)

= 306g
Molar conc = \(frac{Mass conc}{Molar mass}\)
Molar conc = \(frac{306}{122.5}\)

= 2.497mol/dm\(^3\)

2,303.

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

Correct answer is D

No explanation has been provided for this answer.

2,304.

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

Correct answer is C

Fractional distillation with a dehydrant is the most likely separation process to yield high-quality ethanol from palm wine. Adding a dehydrant helps to remove water from the ethanol more effectively during the distillation process, resulting in a higher purity of ethanol. This is important for producing high-quality ethanol suitable for various applications, including consumption or industrial use.

2,305.

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

Correct answer is A

No explanation has been provided for this answer.