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Chemistry
UTME / JAMB 2020
Stoichiometry, Mole Concept & Volumetric Analysis
Solution
Aluminum hydroxide is used in the dyeing industry as a?
A
Dye
B
Dispersant
C
Salt
D
Mordant
medium Difficulty
Verified Correct Answer: Option D
Chemical Principles & Mechanism
Aluminum hydroxide is also used as a mordant in dyeing.
Source: Myschool Past Questions Archive (Record #56822)
Chemistry
UTME / JAMB 2020
Stoichiometry, Mole Concept & Volumetric Analysis
Solution
The most important element on the earth's crust is?
A
Nitrogen
B
Hydrogen
C
Oxygen
D
Fluorine
medium Difficulty
Verified Correct Answer: Option C
Chemical Principles & Mechanism
Oxygen, O2, is by far the most abundant element in earth's crust at 46.6 percent, nearly half of the mass of the crust.
Source: Myschool Past Questions Archive (Record #56823)
Chemistry
UTME / JAMB 2020
Stoichiometry, Mole Concept & Volumetric Analysis
Solution
To obtain pure carbon(ii)oxide from its mixture with carbon(iv)oxide, the mixture should be?
A
Passed over heated copper(ii)oxide
B
Bubbled through water
C
Bubbled through conc H\(_2\)SO\(_4\)
D
Bubbled through conc NAOH
medium Difficulty
Verified Correct Answer: Option D
Chemical Principles & Mechanism
Carbon(ii)oxide is prepared from carbon(iv)oxide by passing the latter through red-hot carbon and the unchanged CO\(_2\) is removed when the mixture of the gases through conc NaOH.
Source: Myschool Past Questions Archive (Record #56824)
Chemistry
WAEC / WASSCE 2020
Organic Chemistry II: Functional Groups, Polymers & Biomolecules
Solution
Which or the following substances is a polypeptide?
A
Starch
B
Glycogen
C
Protein
D
Fats
medium Difficulty
Verified Correct Answer: Option C
Chemical Principles & Mechanism
- A polypeptide is defined as a polymer of amino acids joined together by peptide bonds.
- Proteins are polymers of amino acids.
Source: Myschool Past Questions Archive (Record #58788)
Chemistry
WAEC / WASSCE 2020
Stoichiometry, Mole Concept & Volumetric Analysis
Solution
Which or the following products could be formed during incomplete combustion of a hydrocarbon.
i.Carbon ii. Hydrogen III. Carbon (Il) oxide
A
I only
B
I and II only
C
I and III only
D
II and III only
medium Difficulty
Verified Correct Answer: Option C
Chemical Principles & Mechanism
Incomplete combustion occurs when the supply of air or oxygen is poor. Water is still produced, but carbon monoxide and carbon are produced instead of carbon dioxide. The carbon is released as soot.
Source: Myschool Past Questions Archive (Record #58794)
Chemistry
WAEC / WASSCE 2020
Stoichiometry, Mole Concept & Volumetric Analysis
Solution
What quantity of electrons is lost when one mole of iron (II) ions is oxidized to iron (III) ?
A
0 mole
B
I mole
C
2 moles
D
3 moles
medium Difficulty
Verified Correct Answer: Option B
Chemical Principles & Mechanism
Fe\(^{2+}\) → Fe\(^{3+}\)
The pale greenFe\(^{2+}\) is oxidized to orange Fe\(^{3+}\) because it loses an electron.
Source: Myschool Past Questions Archive (Record #58796)
Chemistry
WAEC / WASSCE 2020
Electrolysis & Electrochemical Cells
Solution
What is the mass of silver deposited when 24,125 C of electricity is passed through a solution or silver salt.
[Ag = 108, IF = 96,500 C ]
A
432g
B
108g
C
54g
D
27g
medium Difficulty
Verified Correct Answer: Option D
Chemical Principles & Mechanism
Ag + e → Ag
1 mole of Ag+ = 108
i.e 108 X 1 X 96500
But, 24,125C will produce ( 108 X 24,125 ) / ( 1 X 96500 )
Ag = 27g
Source: Myschool Past Questions Archive (Record #58797)
Chemistry
WAEC / WASSCE 2020
Reaction Rates & Chemical Equilibrium
Solution
Equal masses of calcium trioxocarbonate(iv) were added to dilute hydrochloric acid at the temperature specified. Under which of the following conditions would the reaction be slowest?
A
Calcium trioxocarbonate ( iv ) chips a 20°C
B
CalcIum trioxocarbonate (IV) chips at 40°C
C
Calcium trioxocarbonate (IV) powder at 20'C
D
Calcium trioxocarbonate (IV) powder at 40'C
medium Difficulty
Verified Correct Answer: Option A
Chemical Principles & Mechanism
- Increasing the surface area of a reactant increases the frequency of collisions and increases the reaction rate.
- Chips have a lower surface area compared to powder, so it accounts for the slowest
Source: Myschool Past Questions Archive (Record #58798)
Chemistry
WAEC / WASSCE 2020
Stoichiometry, Mole Concept & Volumetric Analysis
Solution
Which of the following substances is an example of a fine chemical?
A
Sodium hydroxide
B
Hydrochloric acid
C
Ethylene
D
Ammonia
medium Difficulty
Verified Correct Answer: Option C
Chemical Principles & Mechanism
Fine chemicals are complex, single, pure chemical substances, produced in limited quantities while Heavy chemicals are produced and handled in large lots and are often in a crude state. Some examples of heavy chemicals are ammonia, sulfuric acid, and sodium hydroxide.
Unfortunately, all the substances provided in the options are heavy chemicals.
Source: Myschool Past Questions Archive (Record #58770)
Chemistry
WAEC / WASSCE 2020
Stoichiometry, Mole Concept & Volumetric Analysis
Diagram
Solution
The IUPAC name of the compound represented by the structure below is ?
Attached Figure / Diagram
A
2- chloro but-I ,3-diene.
B
But-1,3-chlorodiene.
C
2-chloro but-diene.
D
3 -chloro but -1.3-diene.
medium Difficulty
Verified Correct Answer: Option A
Chemical Principles & Mechanism
Firstly, we identify the parent name. Here, how many Carbon atoms do we have? Four carbon atoms, i.e But...
However, because there are two C=C double bonds on C-1 and C-3, the parent name will be but,1,3- diene.
Secondly, we identify the substituent group present, which is Chlorine present on C-2 i.e 2- Chloro
Finally, join the two names to get the IUPAC Nomenclature of the compound. i.e 2-chloro but-1,3 diene.
Hence, the correct answer is option A.
Source: Myschool Past Questions Archive (Record #58781)
Chemistry
WAEC / WASSCE 2020
Organic Chemistry II: Functional Groups, Polymers & Biomolecules
Solution
The high solubility of ethanol in water is due to?
A
its low boiling point.
B
its low freezing point.
C
its covalent nature
D
hydrogen bonding
medium Difficulty
Verified Correct Answer: Option D
Chemical Principles & Mechanism
Ethanol is an alcohol that is soluble in water. This is because of the hydroxyl group (−OH) in the ethanol that is able to form hydrogen bonds with the water (H2O) molecules.
Source: Myschool Past Questions Archive (Record #58799)
Chemistry
WAEC / WASSCE 2020
Periodic Table & Periodicity
Solution
Which of the following pairs of properties of alkali metals decreases down the group?
A
First ionization energy and reactivity
B
melting point and atomic radius
C
Reactivity and electronegativity
D
First ionization energy and melting point
medium Difficulty
Verified Correct Answer: Option D
Chemical Principles & Mechanism
- The ionization energy of an atom is the amount of energy that is required to remove an electron from a mole of atoms in the gas phase:
- It is possible to remove more electrons from most elements, so this quantity is more precisely known as the first ionization energy, the energy to go from neutral atoms to cations with a 1+ charge.
- The ionization energy decreases from top to bottom in groups, and increases from left to right across a period.
- The boiling and melting points decrease as you move down the group.
Source: Myschool Past Questions Archive (Record #58803)
Chemistry
WAEC / WASSCE 2020
Nature of Matter & Separation Techniques
Solution
The most suitable process of obtaining water from an aqueous solution of sugar i
A
Crystallization
B
Distillation
C
Filtration
D
Decantation
medium Difficulty
Verified Correct Answer: Option B
Chemical Principles & Mechanism
- Crystallization is primarily employed as a separation technique to obtain pure crystals of a substance from an impure mixture.
- Another important application of crystallization is its use to obtain pure salt from seawater.
- Simple syrup crystallizes when enough of the sugar molecules stick to one another that they become insoluble in the water
note; distillation is used to obtain a solvent from a solution.
Source: Myschool Past Questions Archive (Record #58816)
Chemistry
WAEC / WASSCE 2020
Chemical Bonding & Intermolecular Forces
When an ionic bond is broken, bonding electrons are
A
shared between participating atoms
B
gained by the most electropositive atom
C
gained by the most electronegative atom
D
lost by both participating atoms.
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 #58825)
Chemistry
WAEC / WASSCE 2020
Oxidation, Reduction & Redox Reactions
Solution
The oxidation state of chlorine in NaClO\(_3\) is?
A
+1
B
+3
C
+5
D
+6
medium Difficulty
Verified Correct Answer: Option C
Chemical Principles & Mechanism
the oxidation number of chlorine in NaClO3 is +5.
Source: Myschool Past Questions Archive (Record #58839)