2018 WAEC CHEMISTRY OBJ/THEORY ANSWERS-MAY/JUNE

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 thefermentation process, creating beer, wine, bread, kimchi, yogurt and other foods. Fermentation comes from the Latin word fermentare, meaning “to leaven.

(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

1d===

1e) A catalyst increases the rate of reaction by lowering the activation energy of the reaction

 1fi) CH3COOH + NH3 → CH3COONH2 + H2(g)

fii)
Ethanamide


1g)
i. It has a light weight
ii. It has resistance to rusting
iii. It has a greater tensile strenght


(2ai)
Collision theory states that the rate of a reaction depends on the rate of collision of the reactant molecules. Hence effective collision determines the rate of the reaction because it is the collision that leads to the formation of a product.

(2aii)
When the rate of collision increases, the rate at which molecules collide with each other will also increase thereby making the kinetic energy of the molecules to also increase. The temperature will also increase because temperature is a measure of average kinetic energy.

(2bi)
Draw your diagram

(2bii)
C2H5OH + 3O2 ---->2CO2 + 3H2O
1mole of ethanol = 3moles of O2
2.5moles of ethanol will require 3 × 2.5/1 = 7.5moles of O2.
but 1 mole of gas = 22.4dm3
7.5moles = 7.5 × 22.4 = 168dm3 of O2.

(2Ci)
Esterification is the formation of an Ester by the reaction between Alkanol and an acid.

(2cii) Two uses of alkanols
(i)  They are used as solvents for cellulose
(ii) They are uses in making perfumes and cosmetics.
(iii)  They are used for quick drying of paints and nail varnishes.

(2ciii)
Sodium Ethanoate

(2di)
Tin

(2dii )
This is because the galvanized plate is corrosion-resistant. It has a protective coating which prevents further oxidation of the metal.

4bii)
T 1 =12 degree = 285 k
P 1 =690 mm Hg
V 1 =30 cm ^3
T 2 =273 k
P 2 =760 mmhg
V 2 =?
Using the general gas law
V 1 P 1 / T 1 = V 2 P 2 / T 2
V 2 =30 * 690 *273 / 285 * 760
V 2 =261 cm ^ 3
V 2 =26 cm ^3

4ci)
Cl 2 ( q ) + H 2 O ( i ) - - - - - - >HCL
( aq ) + HOCL( aq )

4cii)
litmus turn red because of the presence of the acid HCL

4di)
chlorine bromine iodine / increasing
boiling point

4dii)
because water has two ( 2 ) ion pairs of
electrons as compared to ammonia which had one