WAEC Chemistry Past Questions & Answers - Page 209

1,041.

Which of the following is correct about both compounds show below? CH3CH 2CH2OH;CH 3
CH 2CH(OH)CH3

A.

They have identical physical properties

B.

They are structural isomers

C.

Their general molecular formula is the same

D.

They are oxidized to alkanones

Correct answer is C

No explanation has been provided for this answer.

1,042.

C8H18 will undergo the following reactions except

A.

cracking

B.

combustion

C.

substitution

D.

addition

Correct answer is D

No explanation has been provided for this answer.

1,043.

Which of the following procedures is suitable for identifying the food colouring added to a pastry sample?

A.

carry out some food tests

B.

examine the pastry sample under a microscope

C.

Do a chromatogram of the colouring extract

D.

determine the molar mass of the colouring

Correct answer is C

Chromatography is used for quality control in the food industry, by separating and analyzing additives, vitamins, preservatives, proteins, and amino acids. It can also separate and detect contaminants such as aflatoxin, a cancer-causing chemical produced by a mold on peanuts.

1,044.

Which of the following occurs when a solution of CuSO4 is electrolysed using copper electrodes?

A.

The cathode becomes coated with copper

B.

Both electrodes gain electrons

C.

The blue colour of the solution fades gradually

D.

The anode increases in mass

Correct answer is A

No explanation has been provided for this answer.

1,045.

0.10 mol dm-3 NaCI conducts electricity better than 0.10 mol dm-3 CH3COOH because the solution of NaCI

A.

contains more ions

B.

is neutral to litmus

C.

has a lower molar mass

D.

has a higher pH

Correct answer is A

0.10 mol \(dm^{-3}\) NaCI conducts electricity better than 0.10 mol \(dm^{-3}\) \(CH_3COOH\) because the solution of NaCI contains more ions. When an ionic compound like NaCI dissolves in water, it dissociates into its component ions, \(Na^+\) and \(Cl^{-}\)