JAMB Chemistry Past Questions & Answers - Page 252

1,256.

If concentrated sulphric acid is added to sugar and warmed gently, the sugar changes from white to brown and finally to a black mas of carbon. In this reaction, concentrated sulphuric acid is acting as ?

A.

a drying agent

B.

an oxidizing agent

C.

a dehydrated agent

D.

a reducing agent

E.

a hydrolysing agent

Correct answer is C

No explanation has been provided for this answer.

1,257.

Which of the following statements is NOT true of electrovalent compounds?

A.

They are solids

B.

They do not vaporized easily

C.

They usually dissolve in water

D.

The elements forming the compounds normally have their valency electrons in a shared state

E.

They conduct electricity

Correct answer is D

No explanation has been provided for this answer.

1,258.

The number of atoms in one mole of a substance is equal to?

A.

the atomic number

B.

the avogadro number

C.

the gas constant

D.

the number of neutrons

E.

the number of electrons

Correct answer is B

Avogadro's number is defined as the number of elementary particles (molecules, atoms, compounds, etc.) per mole of a substance.

1,259.

Oxidation is the process of?

A.

gain of electrons

B.

loss of electrons

C.

gain of hydrogen

D.

loss of oxygen

E.

addition of an electropositive element to a substance

Correct answer is B

Oxidation is the loss of electrons or an increase in the oxidation state of a chemical or atoms within it. 

1,260.

Sodium and potassium belong to the same group of the Periodic Table. This is because?

A.

both are metals

B.

both are soft and lighter than water

C.

both form cations by losing electrons

D.

both have identical electronic configuration

E.

both react with water vigorously

Correct answer is C

They react easily because they lose their 1 valence electron easily to gain their stable octet configuration. Hence, they form the +1 cation easily.