2020 - JAMB Chemistry Past Questions and Answers - page 3

The addition of conc HCL makes the solution more acidic and the solution falls below the original value

Chromatography is a method of separating mixtures by using a moving solvent on filter paper. 

It is a laboratory technique for the separation of a mixture. The mixture is dissolved in a fluid called the mobile phase, which carries it through a system on which is fixed a material called the stationary phase. Wikipedia

Deliquescence is the process by which a substance absorbs moisture from the atmosphere until it dissolves in the absorbed water and forms a solution. Deliquescence occurs when the vapour pressure of the solution that is formed is less than the partial pressure of water vapour in the air.

Wikipedia

Helium floats because it is buoyant;

The molecules in Helium are lighter than the nitrogen and oxygen molecules of our atmosphere and so they rise above it

32g of CUSO\(_4\) liberate 13.0kj of heat

Molar mass of CUSO\(_4\) = 160g

No. of moles of CUSO\(_4\)  = 32g

No. of moles = 32(mass) / 160(molar mass)

= 0.2 moles

i.e 0.2 = 13kj

1 moles = xkj

65KJ 

***

Which gives formula of the Chloride = MCl\(_3\)

4OH ⇒ 2H\(_2\)O + O\(_2\) + 4e-  ........ (i)

From equation (i):

1 mole of Oxygen requires 4e 

i.e 1 mole of Oxygen requires 4F,

where 1F = 96,500 C

[ 4 X 96,500 X 0.125 ] ÷ 1

= 48,250 C

The addition of hydrogen cyanide to a carbonyl group of an aldehyde or most ketones produces a cyanohydrin.

Sterically hindered ketones, however, don't undergo this reaction. Aldehydes and ketones react with primary amines to form a class of compounds called imines, however, Imines of aldehydes are relatively stable while those of ketones are unstable.

Vulcanization of rubber is among the several uses of sulfur