2000 CHEMISTRY JAMB PAST QUESTIONS AND ANSWERS

2000 JAMB CHEMISTRY: TYPE A

1.      A mixture of iodine and sulphur crystals can be separated by treatment with__

(a)    Water to filter off sulphur

(b)   Carbon(iv)sukphide to filter off iodine

(c)    Ethanoic acid to filter off sulphur

(d)   Methanol to filter off iodine

Answer: B

2.      Sieving is a technique used to separate mixtures containing solid particles of__

(a)    Small sizes

(b)   Large sizes

(c)    Different sizes

(d)   The same sizes

Answer: C

Explanation: sieving technique makes use of filter of different mesh sizes depending on the substance to be separated. so sieving is used to separate solid particles of different sizes 

3.      Which of the following compound is composed of  Al, Si, O and H?

(a)    Epsom salt

(b)   Limestone

(c)    Clay

(d)   Urea

Answer: C

Explanation: the chemical formula for Epsom salt is MgSO4, limstone is CaCO3, Clay is Al2Si2O5(OH)4 and urea is NH2-NH2

so the answer is C- clay

4.      50cm3 of carbon(II)oxide exploded with 150cm3 of air containing 20% oxygen by volume. Which of the reactant was in excess?

(a)    Carbon(II)oxide

(b)   Carbon(IV)oxide

(c)    Oxygen

(d)   Nitrogen
Answer: C

5.      How many moles of HCl will be required to react with potassium heptaoxodichromate(VI) to produce 3 moles of chlorine?

(a)    14

(b)   12

(c)    11

(d)   10

Answer: A

Explanation: K2Cr2O7 + 14HCl ---->  2CrCl3 + 2KCl + 3Cl2 + 7H2O

6.      The ratio of the initial to the final pressure of a given mass of gas is 1:1.5. Calculate the final volume of the gas if the initial volume was 300cm3 at the same temperature.

(a)    120cm3

(b)   200cm3

(c)    450cm3

(d)   750cm3

Answer: B

Explanation: since temperature is constant we are going to apply Boyle's law...

Which states that;

P1V1= P2V2

Making V2 subject formula, we have V2= P1V1/P2

From the question, P1=1atm, P2=1.5atm and V1= 300cm3.

V2 = 1*300/1.5

                         =200cm3

7.      The partial pressure of oxygen in a sample of Air is 452mmHg and the total pressure is 780mmHg. What is the mole fraction of oxygen?

(a)    0.203

(b)   0.579

(c)    2.030

(d)   5.790

Answer: B

Explanation: mole ratio= partial pressure/total pressure

Mole ratio = 452/780

                   = 0.579mole

8.      The fundamental difference between the three states of matter is the _

(a)    Shape of their particles

(b)   Number of particles in each state

(c)    Shape of the container they occupy

(d)   Degree of movement of their particles
Answer: D

9.      Which of the following statement is correct about the periodic table?

(a)    Elements in the same period have the same number of valence electrons

(b)   The valence electrons of the element in the same period increase progressively across the period

(c)    Element in the same group have the same number of electron shells

(d)   The non-metallic properties of the elements tend to decrease  across each period.

Answer: B

10.  The electronic configuration of ₂₂X²⁺ ion is..

(a)    1s²2s²2p⁶3s²3p⁶4s²3d²

(b)   1s²2s²2p⁶3s²3p⁶4s₂3d¹

(c)    1s²2s²2p⁶3s²3p⁶

(d)   1s²2s²2p⁶3s²3p⁶4s²

Answer: D

11.  Which of the following types of bonding does not involve formation of  new substances?

(a)    Metallic

(b)   Covalent

(c)    Co-ordinate

(d)   Electrovalent

Answer: A

12.  The knowledge of half-life can be used to

(a)    Create an element

(b)   Detect an element

(c)    Split an element

(d)   Irradiate an element

Answer: B

13.  The shapes of CO2, H2O and CH4 respectively are?

(a)    Bent, linear and tetrahedral

(b)   Bent, tetrahedral and linear

(c)    Linear, bent and tetrahedral

(d)   Tetrahedral, linear and bent

Answer: C

14.  The distance between the nuclei of chlorine atom in a chlorine molecule is 0.194nm. the atomic radius of chlorine atom is__

(a)    0.097nm

(b)   0.914nm\

(c)    0.288nm

(d)   2.388nm

Answer: A

Explanation: The atomic radius is taken to be one-half the distance of closest approach between the nucleic of atoms in the elemental substance.

That is,  Atomic radius = 0.194/2

                                           = 0.097nm

15.  The noble gas, argon, is used for__

(a)    Electric arc welding

(b)   Welding brass

(c)    Underwater welding

(d)   Steel welding

Answer: A

16.  A side effect of soft water is that..

(a)    It gives offensive taste

(b)   Excess calcium is precipitated

(c)    It attacks lead contains in pipes

(d)   It encourages the growth of bacteria
Answer: C

17.  Water molecules can be ligands especially when they are bonded to__

(a)    Alkaline earth metals

(b)   Alkali metals

(c)    Transition metals

(d)   Group VII elements

Answer: C

18.  The air pollutant unknown to nature is__

(a)    NO

(b)   CO

(c)    HCHO

(d)   DDT

Answer: C

19.  1.0dm³ of distilled water was used to wash 2.0g of a precipitate of AgCl. If the solubility product of AgCl is 2.0 X 10^-10 mol²/dm⁶, what quantity of silver was lost in the process?

(a)    2.029 X 10^-3 mol/dm³

(b)   1.414 X 10^-3 mol/dm³

(c)    2.029 X 10^-5 mol/dm³

(d)   1.414 X 10^-5 mol/dm³

Answer: D

20.  Hydration of ions in solution is associated with__

(a)    Absorption of heat

(b)   Reduction of heat

(c)    Conduction of heat

(d)   Libration of heat

Answer: D

21.  The diagram is the solubility curve of a solute, X. Find the amount of X deposited when 500cm3 of a solution of X is cooled from 60oC to 20oC.

(a)    0.750 moles

(b)   0.950 moles

(c)    2.375 moles

(d)   4.750 moles

Answer: A

Explanation: From the graph, the solubility at 60oC =5.5mol/dm3.

     20oC = 4.0mol/dm3/1.5mol/dm3

   On cooling from 60oC to 40oC

1000cm3 deposits 1.5 mol/dm3

Therefore, 500cm3 will deposit. 

        1.5/1000 X 500

      = 0.750moles.

22.  HCl_(aq) + H2O_(l) ß--à H3O_(aq) + Cl^-_(aq). In the reaction Cl^- is the ___

(a)    Conjugate acid

(b)   Acid

(c)    Conjugate base

(d)   Base
Answer: C

23.  In which order are the following salts sensitive to light?

(a)    AgI>AgCl>AgBr

(b)   AgCl>AgI> AgBr

(c)    AgBr > AgCl >AgI

(d)   AgCl>AgBr>AgI
Answer: D

24.  The pOH of a solution of 0.25mol/dm3 of hydrochloric acid is ___

(a)    12.40

(b)   13.40

(c)    14.40

(d)   14.60

Answer: B

Explanation: PH = - log[H+]

              H+ = 0.25mol/dm3 = 2.5 X 10^-1

               Log[H+]=log 2.5+log10^-1

                              = 0.4 - 1 = -0.60

PH= 0.60

Since PH+POH = 14

POH =14-PH= 14-0.60=13.40

25.  MnO^-_4(aq) + 8H⁺ + Y --à Mn²⁺_(aq) + 4H2O_(l). Y in the reaction represents__

(a)    2e-

(b)   3e-

(c)    5e-

(d)   7e-
Answer: C = 5e-

26.  1/2Zn²⁺_(aq) +  e- --à Zn²⁺

In the reaction above, calculate the quantity of electricity required to discharge Zinc.

(a)    0.965 x 10⁴C

(b)   4.820 x 10⁴C

(c)    9.650 x 10⁴C

(d)   48.200 x 10⁴C  [96500C/mol]
Answer: C

27.  Given that M is the mass of substance deposited in an electrolysis and Q the quantity of electricity consumed, then  Faraday’s law can be written as_

(a)    Z/Q

(b)   Q/Z

(c)    Z/2Q

(d)   M=QZ
Answer: D

28.  0.46g of ethanol when burned raised the temperature of 50g of water by 14.3K. calculate the heat of combustion of ethanol.

(a)    +33000KJ/mol

(b)   +300KJ/mol

(c)    -300KJ/mol

(d)   -3000KJ/mol [C=12, H=1, O=16, specific heat capacity of water = 4.2j/g/k

Answer: C

Explanation: Final temperature of water=14.3K, mass of water= 50g

Heat evolved= mass X specific heat X temp.

                       = 50 X 4.2 X 14.3 = 3003J

Mass of ethanol burned = 0.46g

Rmm of ethanol = 46g/mol

Therefore, no of moles of ethanol burned

  = 0.46/46

  = 0.01mole

Combustion if 0.01mole ethanol produces 3003J if heat energy

So, 1mole of ethanol will produce 3003/0.01

  = 300300KJ

The standard heat of combustion of ethanol

= -300.3J

29.  Powdered marble reacts faster with hydrochloric acid solution than the granular form because the powdered form has __

(a)    More molecules

(b)   More atoms

(c)    Larger surface area

(d)   Relatively large atoms
Answer: C

30.  The graph that describes a zero order reaction is__

Answer: B

31.  N2(g) + O2(g) ßà 2NO(g) H= +80kJ/mol

In the reaction above, increase in temperature will

(a)    Increase the quantity of N2

(b)   Increase the yield of NO

(c)    Decrease the yield of NO

(d)   Decrease the quantity of O2
Answer: B

32.  For a reaction in equilibrium, the species involved in the equilibrium constant expression are_

(a)    A gaseous and solid species

(b)   Liquid and solid species

(c)    Solid and dissolved species

(d)   Gaseous and dissolved species
Answer: D

33.  A phenomenon where an element exist in different forms in the same physical state is known as__

(a)    Isomerism

(b)   Amorphism

(c)    Allotropy

(d)   Isotopy
Answer: C

34.  The substance often used for vulcanization of rubber is __

(a)    Chlorine

(b)   Hydrogen peroxide

(c)    Sulphur

(d)   Tetraoxosulphate(VI) acid
Answer: C

35.  A gas that is not associated with global warming is_

(a)    CO2

(b)   SO3

(c)    CH4

(d)   H3
Answer: D

36.  The refreshing and characteristic taste  of soda water and other soft drinks is as a result of the presence in them of__

(a)    Carbon (IV) oxide

(b)   Carbon (II) oxide

(c)    Soda

(d)   Glucose
Answer: A

37.  A form of carbon used for absorbing poisonous gases and purification of noble gases is __

(a)    Wood charcoal

(b)   Animal charcoal

(c)    Carbon fibres

(d)   Carbon black
Answer: A

38.  Synthesis gas is mixture of__

(a)    CH₄ AND H₂O

(b)   CH₄ AND H₂

(c)    CO₂ AND H₂

(d)   CO AND H₂
Answer: D

39.  Potassium vapour burns with a ___

(a)    Blue flame

(b)   Brick-red flame

(c)    Violet flame

(d)   Golden-yellow flame
Answer: C

40.  A common characteristics of copper and silver in their usage as coinage metals is that they_

(a)    Have high metallic luster

(b)   Are not easily oxidized

(c)    Are easily oxidized

(d)   Are not easily reduced
Answer: B

41.  Haematite is an ore of__

(a)    Zinc

(b)   Lead

(c)    Iron

(d)   Copper
Answer: C

42.  The least easily oxidized of the metals below is-_

(a)    Ca

(b)   Na

(c)    Zn

(d)   Al
Answer: B

43.  The repeating unit in natural rubber is__

(a)    Alkjyne

(b)   Isoprene

(c)    N-propene

(d)   Neoprene
Answer: B

44.  Unsaturated organic compounds are identified by decolourization of__

(a)    Silver bromide and potassium tetraoxomanganate (VII) solutions

(b)   Bromine water and acidified potassium tetraoxomanganate (VII) solution

(c)    Silver bromide solution and bromine water

(d)   Bromine water and alkaline potassium tetraoxomanganate (VII) solution
Answer: B

45.  The conditions necessary for the extraction of water molecule from two molecules of ethanol are__

(a)    Less acid and lower temperature

(b)   Excess acid and lower temperature

(c)    Excess acid and higher temperature

(d)   Less acid and high temperature
Answer: C

46.  The chlorinated alkaline often used industrially to remove grease is__

(a)    Tetrachloromethane

(b)   Chloromethane

(c)    Trichloromethane

(d)   Dichloromethane
Answer: A

47.  The reaction of carbide with water gives __

(a)    Ethyne

(b)   Ethane

(c)    Ethane

(d)   Ethanol
Answer: A

48.  The compound below is an _

(a)    Ether

(b)   Ester

(c)    Alkanal

(d)   Alkanol
Answer: B

49.  Alkanones are generally obtained by the oxidation of __

(a)    A primary alkanols

(b)   Secondary alkanols

(c)    Tertiary alkanols

(d)   Secondary alkanols
Answer: B

50.  Sucrose is made up of ___

(a)    Glucose and glucose

(b)   Glucose and fructose

(c)    Fructose and fructose

(d)   Galactose and glucose
Answer: B