2018 Waec chemistry obj and theory expo

Chemistry waec obj and theory expo 2018

Waec Expo chemistry 2018 obj and theory chemistry Expo chemistry Expo 2018 theory expo and runz..

chemistry waec 2018 theory expo waec chemistry Expo expo waec chemistry 2018 expo waec theory now expo waec answer now in

1a)A compound is a substance that results from a combination of two or more different chemical element s, in such a way that the atom s of the different elements are held together by chemical bonds that are difficult to bread

1a) Fermentation is the chemical breakdown of a substance by bacteria, yeasts, or other microorganisms, typically involving effervescence and the giving off of heat.

[5a)
1.Water Gas
2.Producer Gas

ii)Water Gas

iii) Both the hydrogen and Carbon(ii) Oxide in water gas burn in air to release a lot of heat,this makes it a better fuel
Iv)

1.Producer Gas
02(g) + N2(g) + 2C(s)-->2CO(g) +N2 + heat

2.Water Gas
C(s) +H2O(g)-->CO(g) + H2(g)

5b(i)Thermoplastics can be soften repeatedly by heat and remoulded..
Thermosets cannot be soften or melted by heat and remoulded once they are formed
ii)i.Bakelite
ii.Polythene
iii)
1.Plastic items can be manufactured at very low costs by using moulds and good manufacturing process
2.Raw materials for the manufacturing of plastics are readily and cheaply available from the refining of crude Oil

3.Plastics can be tailor made to our exact requirements, because of wide applications.

3a)
From the passage of steam through a mass of hot coke at
a very high temperature (about 1000 oC).
The water gas is mixed with more steam and passed over iron
(III) oxide (as catalyst) at 450 o C. More hydrogen is produced
and carbon(II) oxide gets oxidized to carbondioxide. I.e.
The carbondioxide is removed by dissolving the above products in water under 30 atm pressure - CO2 dissolves.
The gas is then passed through copper(I) methanoate in
ammonia solution under pressure to absorb any trace of carbon(II) oxide which might be present as impurity if not
removed - the hydrogen produced is pure.

3aii)
C (s) + H 2 O(g) → CO (g) + H 2(g)
3aiii)
I. by the action of a dilute strong acid on metals, such as zinc:
Ii. by reaction amphoteric metals with a strong base, such as sodium hydroxide:
Iii. by electrolysis of water:

3b)
I. Decrease in temperature shifts reaction towards product
side.
Ii. increase in pressure shifts reaction towards reactant side.
Iii. Increase in concentration of CO product side.

3ci)
Condensation polymerisation is a process whereby many
small monomer molecules join together to form one large polymer, with water, or some other small molecule formed at the same time.

3cii)
I. polyamides
Ii. polyacetals
3ciii) CH3−COO−CH2−CH3,

3d)
Allotropy is the existence of a chemical element in two or more forms, which may differ in the arrangement of
atoms in crystalline solids or in the occurrence of molecules that contain different numbers of atoms.

3dii)
a) diamond,
b) graphite
3diii)
Diamond is used for cutting hard substance.
Graphite is used to
make brake linings, lubricants, and molds in foundries

Section B

2a. The collision theory states that when suitable particles of the reactant hit each other, only a certain percentage of the collisions cause any noticeable or significant chemical change; these successful changes are called successful collisions. The successful collisions must have enough energy, also known as activation energy , at the moment of impact to break the preexisting bonds and form all new bonds. This results in the products of the reaction. Increasing the concentration of the reactant particles or raising the temperature, thus bringing about more collisions and therefore many more successful collisions, increases the rate of reaction.

 1b.i. deltons law of partial pressure tates that in a mixture of non-reacting gases, the total pressureexerted is equal to the sum of thepartial pressures of the individual gases.
[10/04, 14:38] ‪+234 814 918 1912‬: Section B

2a. The collision theory states that when suitable particles of the reactant hit each other, only a certain percentage of the collisions cause any noticeable or significant chemical change; these successful changes are called successful collisions. The successful collisions must have enough energy, also known as activation energy , at the moment of impact to break the preexisting bonds and form all new bonds. This results in the products of the reaction. Increasing the concentration of the reactant particles or raising the temperature, thus bringing about more collisions and therefore many more successful collisions, increases the rate of reaction.

 (1ai)
Fermentation is the process in which a substance breaks down into a simpler substance. Microorganisms like yeast and bacteria usually play a role in the fermentation process, creating beer, wine, bread, yogurt and other foods.

(1aii)
Zymase

(1b)
-The strength of an acid
-The PH of the solution

(1c)
Fe+H2SO4->FESO4 + H2
H2SO4=10cm^3
Concentration=1mol/dm^3
Amount=Vol * Concentration
=10/100*1
=0.01mol
1mol=56g
0.01mol=56*0.01
=0.56g
Mass of unreacted=5-0.056
=4.44g

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(1d)
(i) NaOH(aq)
(ii) Poly-propenitrite

(1e)
A catalyst increases the rate of a chemical by swinging it's activation every.

(1f)
(i) CH3CooH + NH3 ---->CH3CooH2 + H2O
(ii) Ethanoamide

(1g)
(a) It doesn't corrode easily.
(b) it doesn't react with contain inside.
(c) It can stand for a long period of time.

(1h)
(a) Sweet production industries
(b) perfume industries.

(1i)
(a) E
(b)

(1j)
(a) it increases the volume water in ocean and seas.
(b) It causes increase in rainfall and also corrode painted surfaces