2020 - JAMB Chemistry Past Questions and Answers - page 3
A few drop of conc HCL are added to about 10cm\(^3\) of a solution of PH 3.4. The PH of the resulting mixture is?
less than 3.4
greater than 3.4
unaltered
the same as that of the pure water
The addition of conc HCL makes the solution more acidic and the solution falls below the original value
Chromatography is used to separate components of mixture which differ in their rates of ?
diffusion
migration
reaction
sedimentation
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
Deliquescent substances are also?
efflorescent
anhydrous
hygroscopic
insoluble
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.
Helium is used in observation of ballons because it is?
Light and combustible
light and non-combustible
heavy and combustible
heavy and non-combustible
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 anhydrous copper(ii)tetraoxosulphate(vi) dissolved in 1dm\(^3\) of water generated 13.0kj of heat. The heat solution is?
26.0kj/mol
65.0kj/mol
130.0kj/mol
260.0kj/mol
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
A gaseous metallic chloride MCl consists of 20.22% of M by mass. The formula of the chloride is?
[ M = 27, Cl = 35.5]
MCl
MCl\(_2\)
MCl\(_3\)
M\(_2\)Cl\(_6\)
***
| M | Cl | |
| % composition | 20.22 | 79.78 |
| Atomic mass | 27 | 35.5 |
| Mole ratio | 20.22 | 79.78 |
| 27 | 35.5 | |
| 0.75 | 2.25 | |
| Divided | 0.75 | 0.75 |
| 1 | 3 |
Which gives formula of the Chloride = MCl\(_3\)
What quantity of electricity will liberate 0.125 mole of oxygen molecules during the electrolysis of dilute sodium chloride solution?
24,125 C
48,250 C
72,375 C
96,500 C
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
Which of the following types of bonding does not involve the formation of new substances?
Metallic
Covalent
Co-ordinate
Electrovalent
An organic compound that does not undergo a reaction with both hydrogen cyanide and hydroxylamine can be?
Alkene
Alkanal
Alkanone
Alkanoic Acid
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.
The substance often used for vulcanization of rubber is?
Chlorine
Hydrogen peroxide
Sulphur
Tetraoxosulphate(vi) acid
Vulcanization of rubber is among the several uses of sulfur