FREE 2020 WAEC Chemistry Questions and Answers – 2020 WASSCE Expo

West Africa Examination Council, WAEC Chemistry Questions and Answers for 2020 May/June Examination is now available, always subscribe to Examrelief to get the questions and answers before each paper…
 WAEC Chemistry Questions and Answers

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100% VERIFIED CHEMISTRY THEORY ANSWERS

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👑 2020 WAEC CHEMISTRY ANSWERS👑

100% VERIFIED CHEMISTRY OBJ ANSWERS

1-10 CBCCBDADAD
11-20 ACCCDDBDCD
21-30 BABBCCBDAC
31-40 CBACBADBAA
41-50 DBBDCBACCB

100% VERIFIED CHEMISTRY THEORY ANSWERS

(1ai)
Faraday’s First Law of Electrolysis states that the chemical deposition due to the flow of current through an electrolyte is directly proportional to the quantity of electricity (coulombs) passed through it.

(1aii)
Strong electrolytes ionize completely (100%), while weak electrolytes ionize only partially.

(1b)
CHEMICAL PROPERTY OF EHYNE
– COMBUSTION REACTION: Ethyne burns in air with a luminous smoky flame and hence used for lightening purpose.
2C2H2 + 5O2 —–> 4CO2 + 2H2O + heat

(1c)
Unsaturated hydrocarbons are hydrocarbons that have double or triple covalent bonds between adjacent carbon atoms.

(1cii)
CH3COOH + CH3OH–>CH3COOCH3 + H2O

(1ciii)
methly ethanoate

(1d)
By removing the main product continuously.

(1e)
Mzn = 3.75g
Mzn = 65.0g/mol
n= m/M=3.75/65.0
n=0.0577mole
nH² =0.0577mole because the mole ratio is the same
np =n*L
np=0.0577*6.02*10^23
np=3.47*10^22 moles

(1f)
Flooding

(1gi)
Reaction C

(1gii)
Zinc (from + 2 to + 4)

(1hi)
(i)Each spectral line is caused by one electron
(ii)Electron can exist only in circular orbit of definite quantum energy.

(1hii)
It could not account for the spectrum at note complicated atoms

(1i)
(i)Temperature of the reacting system
(ii)Pressure of the reacting system
(iii)Concentration of the reacting system

(1j)
Both liberate carbon(iv) oxide
One produce a chloride salt , the other produce an ethronate salt

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=====SECTION B=====
Answer ANY Three questions in this Section.

(2ai)
isomers

(2aii)
A = trans 1,2 dichloroethane
B=Cis 1,2 dichloroethane

(2aiii)
Yes.

(2aiv)
Because they are isomers. Isomers have same chemical properties but different physical properties.

(2b)
Destroying gaseous emissions
– Boiling is the rapid vaporization of a liquid

(2bii)
– WHEN NACL IS ADDED =>The more salt (or any solute) added to water, the more you raise the boiling point. Reduction of atmospheric pressure => lowering the atmospheric pressure will lower the boiling point of the liquid.

(2c)
A saturated solution contains the maximum amount of solute that will dissolve at that temperature. Any further addition of solute will result in undissolved solid on the bottom of the container. An unsaturated solution contains less than the maximum amount of solute that can be dissolved at that temperature.

(2cii)
-Add solute to a liquid until no more will dissolve. -Solubility often increases with temperature, so you may be able to get more solute into a hot solvent than you would if – Increase in pressure the solvent was cool

(2cii)
Temperature and Pressure.
Temperature affects the solubility of both solids and gases,
-Pressure only affects the solubility of gases

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(3ai)
Diagram [CLICK HERE]

(3aii)
I. Activation Energy = (210 – 100)KJ = 110K
II. Hp – HR = ΔH
54 – 100 = -46KJ

(3aiii)
Q2(g) + R2(g) –> 2QR(g)

(3aiv)
Exothermic reaction.

(3av)
The heat content of the reactant is higher than that of the product.

(3bi)
E7 – 1s² 2S² 2P³
F9 – 1s² 2S² 2P⁵
G12 – 1S² 2S² 2P⁶ 3S²
H13 – 1S² 2s² 2P⁶ 3S² 3P¹

(3bii)
I. G and H
II. H
III. F
IV. GF2

(3ci)
Isotopy is the existence of an element in more than one physical form with the same atomic number but different atomic masses.

(3d)
(i) Atoms
(ii) Molecules
(iii) ions
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(4ai)
I. potassium tetraoxomanganate (VII)
(ii) Hydrochloric acid
II. concentrated tetraoxosulphate (VI) acid
III. Downward delivery

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(4aii)
2KMn04 (aq) + 16 HCL (as) —-> 2mnCl2(aq) + 2kcl (aq) + 8H20(l) + 5Cl2(g)

(4aiii)
3cl2(g) + 6 Na0H(aq) —-> Nacl03 (aq) + 5Nacl(aq) + 3H20(l)

(4bi)
(i) Iron III oxide
(ii) Coke
(iii) Limestone

(4biii)
Pig iron

(4biv)
The iron has a relatively low melting point because it contains impurities

(4c)
(i) It is not dissolve directly in water because the heat evolved during the process would cause the acid solution to boil, producing a mist at acid droplets which would spread throughout the factory

(ii) It is regarded as a heavy chemical because it is produced in very large quantities and used in many chemical processes.

(iii)
(i) displacement reaction
(ii) As an oxidizing agent

(4d)
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(5ai)
(i) Ammonia (NH3)
(ii) hydrogen chloride gas (Hcl)

(5aii)
To show that hydrogen chloride is extremely soluble in water

(5aiii)
Fill a round-bottomed flask with dry hydrogen chloride through a tube A and air through another tube B. Add a few drops of water through B and close the tubes. Invert the flask into A through water containing blue litmus solution. The water turns red.

(5bi)
(i) Petrochemical industries
(ii) pharmaceutical industries

(5bii)
(i) pollution of water bodies by chemical waste
(ii) pollution of the air
(iii) Radioactive particles are released

(5ci)
(i) Coke
(ii) Coal tar
(iii) Coal gas

(5cii)
(i) Coal gas —-> Important gaseous fuel
(ii) Coke —-> Used as a reducing agent
(iii) Coal tar —-> It may be applied to the affected area to treat psoriasis and seborrheic dermatitis (dandruff).

(5di)
(i) calcium
(ii) magnesium

(5dii)
(i) ion-exchange resin
(ii) reverse osmosis.
(iii) precipitation methods

(5diii)
(i) Calcium ions in the water are good for children’s teeth and bones.
(ii) Limescale (a hard crust) forms inside kettles.
(iii) This wastes energy whenever you boil a kettle. It helps to reduce heart disease.

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