JAMB Chemistry Past Questions & Answers - Page 225

1,121.

What reaction takes place when palm-oil is added to potash and foam are observed?

A.

Neutralization

B.

Saponification

C.

Esterification

D.

Salting-out

Correct answer is B

The reaction of palm oil with potash is known as saponification reaction, palm oil serves as the organic acid(palmitic acid) while potash( conc. KOH) serves as the base leading to the formation of soap(the presence of bubbles indicate the formation of soap)

1,122.

Which of the following is used as an 'anti-knock' in automobile engines?

A.

Tetramethyl silane

B.

Lead tetra-ethyl

C.

Glycerol

D.

n-heptane

Correct answer is B

knocking, in an internal-combustion engine, sharp sounds caused by premature combustion of part of the compressed air-fuel mixture in the cylinder.

Knocking is a phenomenon that occurs in a gasoline engine if the fuel used does not have a high enough octane rating.

Anti – knocking agents are chemical compounds added in the fuels that help in effective combustion.

An antiknock agent is a gasoline additive used to reduce engine knocking and increase the fuel's octane rating by raising the temperature and pressure at which auto-ignition occurs.

Examples are: 

  • Methylcyclopentadienyl manganese tricarbonyl (MMT)
  • Ferrocene.
  • Iron pentacarbonyl.
  • Toluene.
  • Isooctane.
  • Ethanol boosts the octane number of fuel, which helps prevent pre-ignition knock.

  • Organic lead (tetraethyl lead) is used as an antiknock agent in gasoline and jet fuels.

1,123.

Which of the following is NOT correct test for the named organic compound in each case?

A.

Butanoic acid solution gives effervescence with Na2CO3 solution

B.

Glucose when reacted with Na2CrO4 at 0°C will show immediate discharge of colour

C.

When but-2-ene is reacted with dilute solution of KMnO4 the purple colour of KMnO is discharged readily even room temperature

D.

When butan-2-ol is boiled with butanoic acid with a drop of concentrated H2SO4 a sweet smelling liquid is produced

Correct answer is B

No explanation has been provided for this answer.

1,124.

How will a metal X, which reacts explosively with air and with dilute acids be best extracted from its ores?

A.

Electrolysis of solution of its salts

B.

Decomposition of its oxides

C.

Displacement from solution by an alkali metal

D.

Electroiysis of fused salt

Correct answer is D

No explanation has been provided for this answer.

1,125.

Which of the following compounds would give lilac flame coloration and a white precipitate with acidified barium chloride solution?

A.

KCI

B.

NaNO3

C.

K2SO4

D.

CaSO4

Correct answer is C

No explanation has been provided for this answer.