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.

346.

Equal masses of calcium trioxocarbonate(iv) were added to dilute hydrochloric acid at the temperature specified. Under which of the following conditions would the reaction be slowest?

A.

Calcium trioxocarbonate ( iv ) chips a 20°C

B.

CalcIum trioxocarbonate (IV) chips at 40°C

C.

Calcium trioxocarbonate (IV) powder at 20'C

D.

Calcium trioxocarbonate (IV) powder at 40'C

Correct answer is A

- Increasing the surface area of a reactant increases the frequency of collisions and increases the reaction rate.

- Chips have a lower surface area compared to powder, so it accounts for the slowest

347.

What is the mass of silver deposited when 24,125 C of electricity is passed through a solution or silver salt.

[Ag = 108, IF = 96,500 C ]

A.

432g

B.

108g

C.

54g

D.

27g

Correct answer is D

Ag + e → Ag

1 mole of Ag+ = 108

i.e 108 X 1 X 96500

But, 24,125C will produce ( 108 X 24,125 ) / ( 1 X 96500 )

Ag = 27g

348.

What quantity of electrons is lost when one mole of iron (II) ions is oxidized to iron (III) ?

A.

0 mole

B.

3 moles

C.

I mole

D.

2 moles

Correct answer is B

Fe\(^2^+\) → Fe\(^3^+\)

The pale green Fe2+ is oxidized to orange Fe3+ because it loses an electron.

349.

Which or the following products could be formed during incomplete combustion of a hydrocarbon.

i.Carbon ii. Hydrogen III. Carbon (Il) oxide

A.

I only

B.

I and II only

C.

I and III only

D.

II and III only

Correct answer is C

Incomplete combustion occurs when the supply of air or oxygen is poor. Water is still produced, but carbon monoxide and carbon are produced instead of carbon dioxide. The carbon is released as soot.

350.

Which or the following substances is a polypeptide?

A.

Starch

B.

Glycogen

C.

Protein

D.

Fats

Correct answer is C

- A polypeptide is defined as a polymer of amino acids joined together by peptide bonds.

Proteins are polymers of amino acids.