WAEC 2024 CHEMISTRY ANSWER


CHEMISTRY OBJ
1-10: BCBDBACCCB
11-20: CACCDCBCAB
21-30: BBCCBDDDCD
31-40: BCADDAACAC
41-50: BCBCDBCADA


(1)




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(2a)
(I)Deliquescence is the process by which a substance absorbs moisture from the atmosphere until it dissolves in the absorbed water and forms a solution. This typically occurs with hygroscopic substances that have a high affinity for water.

(II)Efflorescence is the process by which a substance loses water to the atmosphere, resulting in the formation of a powdery surface deposit. This occurs when the vapor pressure of the water in the hydrated salt is greater than the partial pressure of water vapor in the air.

(2aii)
(I)Deliquescence: Calcium chloride (CaCl?)
(II)Efflorescence: Sodium carbonate decahydrate (Na?CO?·10H?O)

(2bi)
Ionization energy is the amount of energy required to remove an electron from an isolated gaseous atom or ion in its ground state. The first ionization energy refers to the energy needed to remove the first electron, while subsequent ionization energies refer to the removal of additional electrons.


(2bii)
The second ionization energy of sodium is greater than the first because, after the first electron is removed, the remaining electrons are closer to the nucleus and experience a stronger attractive force. Removing a second electron requires more energy as it disrupts the stable, noble gas configuration left behind.


(2ci)
Charles' Law states that the volume of a given mass of gas is directly proportional to its absolute temperature, provided the pressure remains constant. Mathematically, it is expressed as:
V/T = k






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BONUS ANSWER

(3ai)
I. Direct combination of constituent elements:
The direct combination reaction involves lead and chlorine gas.
Pb(s)+Cl?(g) ---> PbCl?(s)

II. Double decomposition:
The double decomposition reaction can be achieved by reacting lead (II) nitrate with sodium chloride.
Pb(NO?)?(aq)+2NaCl(aq) ---> PbCl?(s)+2NaNO?(aq)

III. Displacement reaction:
The displacement reaction can be achieved by reacting lead with hydrochloric acid.
Pb(s)+2HCl(aq) ---> PbCl?(s)+H?(g)

(3aii)
I. Direct combination of constituent elements:
Increasing the temperature would increase the rate of reaction. Higher temperatures provide more kinetic energy to the reacting particles, increasing the chances of successful collisions.

II. Double decomposition:
Increasing the concentration of the reactants (lead (II) nitrate and sodium chloride) would increase the rate of reaction. Higher concentrations lead to more frequent collisions between reacting particles.

III. Displacement reaction:
Increasing the surface area of lead by using powdered lead instead of a solid block would increase the rate of reaction. A greater surface area allows more reactant particles to collide simultaneously.

(3bi)
(i) Increase Pressure
(ii) Decrease Temperature

(3bii)
First, determine the limiting reactant by comparing the mole ratio:
2SO?+O?-->2SO?

From the balanced equation:
2 volumes of SO? react with 1 volume of O?

Given:
SO?= 60 cm³
O?= 40 cm³

Required O?=60cm³/2= 30cm³

Since 30cm³ of 02 is required but 40cm³ is available, SO? is the limiting reactant.

Volume of SO? formed: 60cm³SO? ---> 60cm³SO?.

Volume of residual O?:
Initial O? - Reacted O? = 40cm³ - 30cm³

Total residual gas volume:
Residual O?=10cm³


(3biii)
-Oxidation number of sulfur in SO?: +4
-Oxidation number of sulfur in SO?: +6

Change in oxidation number:
+6-(+4)= +2

(3c)
Diagram

Cyclopropane has the molecular formula C3H6 with a ring structure WHILE n-Propane has the molecular formula C3H8 with a linear structure.

(3di)
-Compound X: Propanol (or specifically, 1-propanol)
-Compound Y: Propyl butanoate

(3dii)
hydroxyl group (-OH)

(3diii)
CH?H?OH +CH?H?O? ---> C?H4O? +H?O

(3c)


(3di)
-Compound X: Propanol (or specifically, 1-propanol)
-Compound Y: Propyl butanoate

(3dii)
Hydroxyl group (-OH)

(3diii)
CH?H?OH +CH?H?O? ---> C?H4O? +H?O

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