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.

631.

The alkanoic acid found in human sweat is

A.

CH\(_3\)-COOH

B.

CH\(_3\)—CH\(_2\)—COOH

C.

H-COOH

D.

CH\(_3\)

Correct answer is B

Bacteria of the genus Propionibacterium produce propionic acid (Propanoic Acid) as the end-product of their anaerobic metabolism. This class of bacteria is commonly found in the stomach of ruminants and the sweat glands of humans, and their activity is partially responsible for the odour of both Swiss cheese and sweat.

632.

The general formula of alkanones is

A.

RCHO

B.

R\(_2\)CO

C.

RCOOH

D.

RCOOR

Correct answer is B

Alkanones also known as ketones have the general formula R\(_2\)CO

633.

The situation obtained when a perfect gas expands into a vacuum is

A.

ΔH is positive and TΔ S is zero

B.

ΔH is positive and T Δ S is negative

C.

ΔH is negative and TΔ S is zero

D.

ΔH is zero and T Δ S is positive

Correct answer is D

The definition of enthalpy change is

  ΔH = ΔU + Pex(ΔV)

  The enthalpy change is zero because both terms on the right are zero in free expansion of an ideal gas.

  There is no external pressure in a free expansion, so P (ex) = 0. And the internal energy change, ΔU of free expansion in a closed system is zero since no inter molecular forces have to be overcome. The temperature remains constant and no heat is absorbed or released.

634.

3H\(_{2(g)}\)+ N\(_{2(g)}\)⇔ 2NH\(_{3(g)}\) ; H= -ve
In the reaction above, lowering of temperature will

A.

have no effect on the equilibrium position

B.

increase the rate of both the forward and reverse reactions equally

C.

favour the forward reaction

D.

favour the reverse reaction

Correct answer is C

N\(_{2(g)}\) + 3H\(_{2(g)}\) ⇔ 2NH\(_{3(g)}\) In the Haber process, the forward reaction is exothermic and the backward reaction is endothermic. If the temperature is decreased, the yield from the exothermic direction is increased i.e. the forward reaction is increased.

635.

Sieving is a technique used to separate mixtures containing solid particles of

A.

small sizes

B.

large sizes

C.

different sizes

D.

the same size

Correct answer is C

Sieving is a simple and convenient technique of separating particles of different sizes.