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Chemistry
UTME / JAMB 2023
Atomic Structure and Periodic Table
Solution
Which type of chemical combination involves the transfer of electrons from one atom to another, resulting in the formation of oppositely charged ions?
A
Ionic bonding
B
Hydrogen bonding
C
Covalent bonding
D
Metallic bonding
medium Difficulty
Verified Correct Answer: Option A
Chemical Principles & Mechanism
Ionic bonding occurs between a metal and a non-metal. The metal atom donates one or more electrons to the non-metal atom, resulting in the formation of positively charged cations and negatively charged anions. These oppositely charged ions are held together by electrostatic forces to form an ionic compound.
Source: Myschool Past Questions Archive (Record #67435)
Chemistry
UTME / JAMB 2023
Organic Chemistry
Solution
Which of the following alkanes has a straight-chain structure?
A
Cyclopentane (C5H10)
B
Isobutane (C4H10)
C
2 - methyl propane (C4H10)
D
Pentane (C5H12)
medium Difficulty
Verified Correct Answer: Option D
Chemical Principles & Mechanism
Pentane (C5H12) is a straight-chain alkane. Alkanes are hydrocarbons with the general formula CnH2n+2. They are called straight-chain alkanes if all the carbon atoms are connected in a continuous chain without any branches. Butane and Isobutane are both C4H10, but Isobutane has a branched structure, not a straight chain. Cyclopentane (C5H10) is a cycloalkane, not a straight-chain alkane.
Source: Myschool Past Questions Archive (Record #67443)
Chemistry
UTME / JAMB 2023
Electrochemistry and Redox
Solution
What is the product of the electrolysis of aqueous sodium chloride (NaCl) using inert electrodes?
A
Hydrogen gas at the cathode and chlorine gas at the anode
B
Hydrogen gas at the cathode and oxygen gas at the anode
C
Sodium metal at the cathode and chlorine gas at the anode
D
Sodium metal at the cathode and oxygen gas at the anode
medium Difficulty
Verified Correct Answer: Option B
Chemical Principles & Mechanism
During the electrolysis of aqueous sodium chloride using inert electrodes (such as platinum or carbon), the cations (H\(^+\)) are attracted to the cathode and are reduced to form hydrogen gas (H\(_2\)). The anions (OH\(^-\)) are attracted to the anode and are oxidized to form oxygen gas (O\(_2\)).
Source: Myschool Past Questions Archive (Record #67446)
Chemistry
UTME / JAMB 2023
Acids, Bases, and Salts
Solution
When an acidic solution is diluted, what happens to its pH?
A
It depends on the specific acid
B
It decreases
C
It remains the same
D
It increases
medium Difficulty
Verified Correct Answer: Option D
Chemical Principles & Mechanism
When an acidic solution is diluted by adding more solvent (usually water), the concentration of hydrogen ions (H\(^+\)) decreases. As a result, the pH of the solution increases, making it less acidic
Source: Myschool Past Questions Archive (Record #67448)
Chemistry
UTME / JAMB 2023
Stoichiometry & Mole Concept
Solution
Which of the following factors does NOT affect the rate of a chemical reaction?
A
Concentration of reactants
B
Presence of a catalyst
C
Molecular weight of products
D
Temperature
medium Difficulty
Verified Correct Answer: Option C
Chemical Principles & Mechanism
The molecular weight of products is not directly related to the rate of a chemical reaction. The factors that affect the reaction rate include concentration of reactants, temperature, presence of catalysts, surface area, and the nature of the reactants and products.
Source: Myschool Past Questions Archive (Record #67450)
Chemistry
UTME / JAMB 2023
Organic Chemistry
Solution
Which organic compound is responsible for the characteristic aroma of fruits?
A
Alkane
B
Alkyne
C
Ester
D
Amine
medium Difficulty
Verified Correct Answer: Option C
Chemical Principles & Mechanism
Esters are organic compounds that have a pleasant, fruity aroma. They are responsible for the characteristic smells of fruits and many other fragrant substances.
Source: Myschool Past Questions Archive (Record #67452)
Chemistry
UTME / JAMB 2023
Stoichiometry & Mole Concept
Solution
What is the molar mass of water (H2O)?
A
18 g/mol
B
22 g/mol
C
16 g/mol
D
12 g/mol
medium Difficulty
Verified Correct Answer: Option A
Chemical Principles & Mechanism
The molar mass of water (H2O) is calculated by adding the atomic masses of its constituent elements: 2 hydrogen atoms (each with a molar mass of approximately 1 g/mol) and 1 oxygen atom (with a molar mass of approximately 16 g/mol). Therefore, the molar mass of water is 2 x 1 g/mol + 1 x 16 g/mol = 18 g/mol.
Source: Myschool Past Questions Archive (Record #67453)
Chemistry
UTME / JAMB 2023
Matter & Separation Techniques
Solution
What is the chemical formula of rust, which is formed on the surface of iron in the presence of oxygen and moisture?
A
Fe\(_3\)O\(_4\)
B
FeO
C
Fe(OH)3
D
Fe\(_2\)O\(_3\)
medium Difficulty
Verified Correct Answer: Option D
Chemical Principles & Mechanism
Rust is a reddish-brown compound that forms on the surface of iron in the presence of oxygen and moisture. Its chemical formula is Fe\(_2\)O\(_3\), indicating the presence of two iron atoms and three oxygen atoms in the compound.
Source: Myschool Past Questions Archive (Record #67455)
Chemistry
UTME / JAMB 2023
Atomic Structure and Periodic Table
Solution
How many pi (\(\pi\)) bonds are there in an alkene with six carbon atoms?
A
1
B
6
C
5
D
3
medium Difficulty
Verified Correct Answer: Option A
Chemical Principles & Mechanism
The alkene with six carbon atoms is hexene with the formula C\(_6\)H\(_{12}\).Hexene is an alkene, which means it has one carbon-carbon double bond,C=C and each double bond consists of one sigma bond and one pi bond.
A single bond is a sigma bond.
A double bond consists of one sigma bond and one pi bond.
A triple bond consists of one sigma bond and two pi bonds.
Source: Myschool Past Questions Archive (Record #67457)
Chemistry
UTME / JAMB 2023
Matter & Separation Techniques
Solution
What is the principal ore of iron, from which iron is extracted?
A
Calcite
B
Bauxite
C
Magnetite
D
Hematite
medium Difficulty
Verified Correct Answer: Option D
Chemical Principles & Mechanism
Hematite (Fe\(_2\)O\(_3\)) is the principal ore of iron and is widely mined for the extraction of iron metal.
Source: Myschool Past Questions Archive (Record #67458)
Chemistry
UTME / JAMB 2023
Atomic Structure and Periodic Table
Solution
Which group does calcium belong to in the periodic table?
A
Alkaline earth metals
B
Halogens
C
Alkali metals
D
Noble gases
medium Difficulty
Verified Correct Answer: Option A
Chemical Principles & Mechanism
Calcium belongs to the alkaline earth metals group in the periodic table. It is located in Group 2 and has two valence electrons.
Source: Myschool Past Questions Archive (Record #67459)
Chemistry
UTME / JAMB 2023
Matter & Separation Techniques
Solution
Which of the following is a primary constituent of crude oil?
A
Pentane
B
Ethanol
C
Heptane
D
Methane
medium Difficulty
Verified Correct Answer: Option D
Chemical Principles & Mechanism
Crude oil is a mixture of hydrocarbons of various chain lengths. methane is one of the primary constituents of crude oil, and it belongs to the group of alkanes.
Source: Myschool Past Questions Archive (Record #67460)
Chemistry
UTME / JAMB 2023
Matter & Separation Techniques
Solution
What is the main source of carbon monoxide (CO) in urban areas?
A
Volcanic eruptions
B
Vehicle emissions
C
Forest fires
D
Industrial processes
medium Difficulty
Verified Correct Answer: Option B
Chemical Principles & Mechanism
The main source of carbon monoxide (CO) in urban areas is vehicle emissions, especially from incomplete combustion of gasoline and diesel in engines.
Source: Myschool Past Questions Archive (Record #67461)
Chemistry
UTME / JAMB 2023
Stoichiometry & Mole Concept
Solution
What is the empirical formula of a compound containing 40.00% carbon, 6.67% hydrogen, and 53.33% oxygen by mass?
A
C\(_4\)H\(_8\)O\(_4\)
B
CH\(_2\)O
C
C\(_2\)H\(_4\)O\(_2\)
D
C\(_3\)H\(_6\)O\(_3\)
medium Difficulty
Verified Correct Answer: Option B
Chemical Principles & Mechanism
To determine the empirical formula, we first need to convert the percentages to moles by assuming a convenient mass for the sample. Let's assume we have 100 grams of the compound.
Mass of carbon = 40.00 grams
Mass of hydrogen = 6.67 grams
Mass of oxygen = 53.33 grams
Now, we calculate the moles of each element:
Moles of carbon = 40.00 g / molar mass of carbon = 40.00 g / 12.01 g/mol ≈ 3.33 mol
Moles of hydrogen = 6.67 g / molar mass of hydrogen = 6.67 g / 1.01 g/mol ≈ 6.60 mol
Moles of oxygen = 53.33 g / molar mass of oxygen = 53.33 g / 16.00 g/mol ≈ 3.33 mol
Now, we find the smallest whole-number ratio of the moles:
C ≈ 3.33 / 3.33 ≈ 1
H ≈ 6.60 / 3.33 ≈ 2
O ≈ 3.33 / 3.33 ≈ 1
Thus, the empirical formula is CH2O.
Source: Myschool Past Questions Archive (Record #67463)
Chemistry
UTME / JAMB 2023
Matter & Separation Techniques
Solution
Which separation technique is used to separate different pigments in a mixture based on their affinity for a stationary phase and a mobile phase?
A
Chromatography
B
Filtration
C
Decantation
D
Distillation
medium Difficulty
Verified Correct Answer: Option A
Chemical Principles & Mechanism
Chromatography is a separation technique used to separate and analyze components of a mixture based on their differential partitioning between a stationary phase (e.g., paper or a column) and a mobile phase (e.g., solvent). Different components move at different rates, leading to separation.
Source: Myschool Past Questions Archive (Record #67464)