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Chemistry
WAEC / WASSCE 2016
Acids, Bases, and Salts
Solution
Which of the following factors will affect the rate of the reaction represented by the following equation?
2HCl(aq) + CaCO3(s) \(\rightarrow\) CaCl2(aq) + H2O(1) + CO2(g)
I. Pressure
II.Concentration
III. Nature of reactants
IV. Temperature
A
I and II only
B
II, III and IV only
C
I, II and III only
D
I, II. III and IV
medium Difficulty
Verified Correct Answer: Option B
Chemical Principles & Mechanism
All others except pressure would affect the equilibrium of the system.
If only the product is gaseous and none of the reactants are gaseous, then pressure will not have a significant effect on the rate of reaction because the pressure change only affects the concentration of gaseous species, and since no reactants are in the gas phase, there's no change in their concentration to influence the reaction rate.
Source: Myschool Past Questions Archive (Record #45202)
Chemistry
WAEC / WASSCE 2016
Stoichiometry & Mole Concept
Solution
On evaporation to dryness, 350cm\(^3\) of saturated solution of salt Z gave 55.5g of salt. What is the solubility of the salt? [Z = 101]
A
1.57 moldm-3
B
3.14 moldm-3
C
6.28 moldm-3
D
12.56 moldm-3
medium Difficulty
Verified Correct Answer: Option A
Chemical Principles & Mechanism
Saturated solution = 350cm\(^3\)
mass of salt Z in saturated solution = 55.5g
Number of moles of salt = \(\frac{55.5}{101}\) = 0.55mole
If 350cm\(^3\) of solution contains 0.55mole
1000cm\(^3\) will contain \(\frac{1000 \times 0.55}{350}\) = 1.57moldm\(^{-3}\)
Alternatively, you can use the formula for solubility which is:
Solubility = \(\frac{mass of solute}{Molar mass of solute}\times\frac{1000}{Volume of solvent}\)
= \(\frac{55.5}{101}\times\frac{1000}{350}\)
= 1.571 moldm\(^{-3}\)
Source: Myschool Past Questions Archive (Record #45203)
Chemistry
WAEC / WASSCE 2016
Acids, Bases, and Salts
Which of the following salts when dissolved in water will form a solution that will change blue litmus to red?
A
CH3COONa
B
NH4Cl
C
NaCl
D
KCl
medium Difficulty
Verified Correct Answer: Option B
Chemical Principles & Mechanism
No expanded working has been attached for this question yet. The verified answer is Option B.
Source: Myschool Past Questions Archive (Record #45204)
Chemistry
WAEC / WASSCE 2016
Atomic Structure and Periodic Table
Which of the following bonds are broken when ethanol is boiled?
I. Covalent bonds
II. Ionic bonds
III. Hydrogen bonds
A
I only
B
II only
C
III only
D
I, II, III
medium Difficulty
Verified Correct Answer: Option C
Chemical Principles & Mechanism
No expanded working has been attached for this question yet. The verified answer is Option C.
Source: Myschool Past Questions Archive (Record #45205)
Chemistry
WAEC / WASSCE 2016
Stoichiometry & Mole Concept
A compound with molecular formula CH2O2 is
A
A Carbohydrate
B
A Carboxylic acid
C
An alkanol
D
An ester
medium Difficulty
Verified Correct Answer: Option B
Chemical Principles & Mechanism
No expanded working has been attached for this question yet. The verified answer is Option B.
Source: Myschool Past Questions Archive (Record #45206)
Chemistry
WAEC / WASSCE 2016
Stoichiometry & Mole Concept
The quality of electricity required to discharge 1 mole of univalent ion is
A
9600C
B
48250C
C
96500C
D
193000C
medium Difficulty
Verified Correct Answer: Option C
Chemical Principles & Mechanism
No expanded working has been attached for this question yet. The verified answer is Option C.
Source: Myschool Past Questions Archive (Record #45207)
Chemistry
WAEC / WASSCE 2016
Matter & Separation Techniques
Chlorine water is used as a bleaching agent because it is
A
An acidic solution
B
An alkaline solution
C
An oxidizing agent
D
A reducing agent
medium Difficulty
Verified Correct Answer: Option C
Chemical Principles & Mechanism
No expanded working has been attached for this question yet. The verified answer is Option C.
Source: Myschool Past Questions Archive (Record #45208)
Chemistry
WAEC / WASSCE 2016
Matter & Separation Techniques
Which of the following substances is a non-electrolyte?
A
H2SO4
B
CH3COOH
C
C6H12O6
D
NH4Cl
medium Difficulty
Verified Correct Answer: Option C
Chemical Principles & Mechanism
No expanded working has been attached for this question yet. The verified answer is Option C.
Source: Myschool Past Questions Archive (Record #45209)
Chemistry
WAEC / WASSCE 2016
Acids, Bases, and Salts
The oxidation number of sulphur is +4 in
A
Na2S>2O3
B
H2SO3
C
H2SO4
D
SO3
medium Difficulty
Verified Correct Answer: Option B
Chemical Principles & Mechanism
No expanded working has been attached for this question yet. The verified answer is Option B.
Source: Myschool Past Questions Archive (Record #45210)
Chemistry
WAEC / WASSCE 2016
Atomic Structure and Periodic Table
Solution
Consider the following ionic equation:
Cr\(_2\)O\(_7\)\(^{2-}\) + 14H\(^+\) + ne- → 2Cr\(^{3+}\) + 7H\(_2\)O.
The value of n in the equation is_______?
A
7
B
6
C
3
D
2
medium Difficulty
Verified Correct Answer: Option B
Chemical Principles & Mechanism
Cr\(_2\)O\(_7\)\(^{2-}\) + 14H\(^+\) + ne- → 2Cr\(^{3+}\) + 7H\(_2\)O.
All you need to do is to balance the chemical equation, balancing the ionic/ number of moles of the electrons on both sides
Cr\(_2\)O\(_7\)\(^{2-}\) + 14H\(^+\) + ne- → 2Cr\(^{3+}\) + 7H\(_2\)O.
(1 x - 2) + (14 x +1) + n = ( 2 x +3)
- 2 + 14 + n = +6
12 + n = + 6
What do we need to the +12 on the left hand side to equate +6 on the right hand side
+12 - 6 = +6
Therefore, number of electrons is 6. i.e 6e\(^-\)
Source: Myschool Past Questions Archive (Record #45212)
Chemistry
WAEC / WASSCE 2016
Atomic Structure and Periodic Table
Solution
Consider the following half-cell reactions.
Al(s) \(\to\) Al3+(aq) + 3e-
Cu2+(aq) + 2e- \(\to\) Cu(s)
The overall equation for the reaction is
A
Al(s) + Cu2+(aq) \(\to\) Al3+(aq) + Cu(s)
B
2Al(s) + Cu2+(aq) \(\to\) 2Al(aq) + Cu(s)
C
2Al(s) + 3Cu2+(aq) \(\to\) 3Cu(s) + 2Al3+(aq)
D
3Al(s) + 2Cu2+(aq) \(\to\) Cu(s) + 3Al3+(aq)
medium Difficulty
Verified Correct Answer: Option C
Chemical Principles & Mechanism
Al(s) \(\to\) Al3+(aq) + 3e- ______(i)
Cu2+(aq) + 2e- \(\to\) Cu(s) ________(ii)
To balance the electrons, multiply equation (i) by 2 and equation (ii) by 3 and then add the resulting equations
2Al(s) \(\to\)2Al3+(aq) + 3e-
3cu2+(aq) + 6e- \(\to\)3Cu(s)
2Al(s) + 3Cu2+(aq) \(\to\) 3Cu(s) + 2Al3+(aq)
Source: Myschool Past Questions Archive (Record #45216)
Chemistry
WAEC / WASSCE 2016
Acids, Bases, and Salts
Amino acids are obtained from proteins by
A
Hydrolysis
B
Oxidation
C
Polymerization
D
Reduction
medium Difficulty
Verified Correct Answer: Option A
Chemical Principles & Mechanism
No expanded working has been attached for this question yet. The verified answer is Option A.
Source: Myschool Past Questions Archive (Record #45278)
Chemistry
WAEC / WASSCE 2016
Stoichiometry & Mole Concept
Solution
When a compound X is heated with concentrated tetraoxosulphate(VI)acid, it produces an alkene. X is an
A
Alkane
B
Alkanol
C
Alkanoate
D
Alkyne
medium Difficulty
Verified Correct Answer: Option B
Chemical Principles & Mechanism
When alcohol reacts with concentrated sulphuric acid, H\(_2\)SO\(_4\), it undergoes a dehydration reaction that removes water molecules. The reaction can produce alkenes or ethers, depending on the conditions.
Concentrated sulfuric acid is a strong oxidizing agent that absorbs water. It removes the hydroxyl (OH) group from the alcohol carbon atom and a hydrogen atom from an adjacent carbon atom.
Alkenes: The reaction can produce alkenes, such as ethene, C\(_2\)H\(_4\), when the alcohol loses water molecules.
Ethers: The reaction can produce Ethers, such as diethyl ether, when two alcohol molecules are dehydrated.
Source: Myschool Past Questions Archive (Record #45281)
Chemistry
WAEC / WASSCE 2016
Matter & Separation Techniques
Ripening of fruits is hastened by using
A
Ethanol
B
Ethane
C
Ethene
D
Ethyne
medium Difficulty
Verified Correct Answer: Option C
Chemical Principles & Mechanism
No expanded working has been attached for this question yet. The verified answer is Option C.
Source: Myschool Past Questions Archive (Record #45282)
Chemistry
WAEC / WASSCE 2016
Acids, Bases, and Salts
Solution
The compound that makes palm wine taste sour after exposure to the air for few days is
A
Ethanol
B
Ethanoic acid
C
Methanol
D
Methanoic acid
medium Difficulty
Verified Correct Answer: Option A
Chemical Principles & Mechanism
The ethanol (alcohol content) of the wine, is oxidized, by the oxygen in the air into ethanoic acid.
Source: Myschool Past Questions Archive (Record #45284)