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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)
Chemistry
UTME / JAMB 2023
Acids, Bases, and Salts
Solution
What is the common name for ethanoic acid?
A
Acetic acid
B
Butyric acid
C
Propionic acid
D
Formic acid
medium Difficulty
Verified Correct Answer: Option A
Chemical Principles & Mechanism
Ethanoic acid is commonly known as acetic acid. It is the main component of vinegar and is used in various industrial processes.
Source: Myschool Past Questions Archive (Record #67466)
Chemistry
UTME / JAMB 2023
Atomic Structure and Periodic Table
Solution
What type of reaction is involved in the formation of alkanols from alkenes?
A
Elimination reaction
B
Redox reaction
C
Substitution reaction
D
Addition reaction
medium Difficulty
Verified Correct Answer: Option D
Chemical Principles & Mechanism
Alkanols can be formed from alkenes through an addition reaction. In this reaction, the carbon-carbon double bond of the alkene is broken, and a hydroxyl group (-OH) is added to one of the carbon atoms, resulting in the formation of an alcohol.
Source: Myschool Past Questions Archive (Record #67467)