Practice post utme redeemers university chemistry 2025 Past Questions

Question 1

A 2.50 g sample of a non-metallic oxide of nitrogen is dissolved in 50.0 cm³ of 0.100 M HCl. The reaction is as follows: NO_x + 2HCl → H_2O + xHCl. If 25.0 cm³ of 0.100 M NaOH is added to the solution, and the excess NaOH is titrated with 25.0 cm³ of 0.100 M HCl, calculate the value of x.

A. 1

Correct B. 2

C. 3

D. 4

Correct Answer: B

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Question 2

The s\tandard enthalpy of formation of CO_2(g) is -393.5 kJ/mol. The s\tandard enthalpy of formation of H_2O(l) is -285.8 kJ/mol. Calculate the s\tandard enthalpy of formation of CH_4(g).

Correct A. -74.8 kJ/mol

B. -74.5 kJ/mol

C. -74.2 kJ/mol

D. -74.9 kJ/mol

Correct Answer: A

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Question 3

A 2.50 g sample of a non-metallic oxide of nitrogen is dissolved in 50.0 cm³ of 0.100 M HCl. The reaction is as follows: NO_x + 2HCl → H_2O + xHCl. If 25.0 cm³ of 0.100 M NaOH is added to the solution, and the excess NaOH is titrated with 25.0 cm³ of 0.100 M HCl, calculate the value of x.

A. 1

Correct B. 2

C. 3

D. 4

Correct Answer: B

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Question 4

The s\tandard enthalpy of formation of CO_2(g) is -393.5 kJ/mol. The s\tandard enthalpy of formation of H_2O(l) is -285.8 kJ/mol. Calculate the s\tandard enthalpy of formation of CH_4(g).

Correct A. -74.8 kJ/mol

B. -74.5 kJ/mol

C. -74.2 kJ/mol

D. -74.9 kJ/mol

Correct Answer: A

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Question 5

A 2.50 g sample of a non-metallic oxide of nitrogen is dissolved in 50.0 cm³ of 0.100 M HCl. The reaction is as follows: NO_x + 2HCl → H_2O + xHCl. If 25.0 cm³ of 0.100 M NaOH is added to the solution, and the excess NaOH is titrated with 25.0 cm³ of 0.100 M HCl, calculate the value of x.

A. 1

Correct B. 2

C. 3

D. 4

Correct Answer: B

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Question 6

Determine the number of moles of oxygen gas (O2) required to completely oxidize 2.50 g of carbon monoxide (CO) according to the balanced equation: 2CO + O2 → 2CO2.

A. 0.125 mol

Correct B. 0.250 mol

C. 0.500 mol

D. 1.00 mol

Correct Answer: B

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Question 7

A sample of hydrogen gas (H2) occupies a volume of 2.50 L at a pressure of 1.00 atm and a temperature of 298 K. What is the number of moles of hydrogen gas present?

A. 0.0100 mol

Correct B. 0.0200 mol

C. 0.0300 mol

D. 0.0400 mol

Correct Answer: B

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Question 8

The element sulfur (S) exists in several allotropes, including rhombic sulfur and monoclinic sulfur. Which allotrope has a higher melting point?

Correct A. Monoclinic sulfur

B. Rhombic sulfur

C. Both have the same melting point

D. Dep\ends on the temperature

Correct Answer: A

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Question 9

A solution contains 0.100 M sodium chloride (NaCl) and 0.0500 M calcium chloride (CaCl2). What is the total concentration of chloride ions \( Cl- \) in the solution?

A. 0.125 M

Correct B. 0.150 M

C. 0.175 M

D. 0.200 M

Correct Answer: B

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Question 10

A 10.0 L sample of a gas at 2.00 atm and 298 K is compressed to 5.00 L at cons\tant temperature. What is the new pressure of the gas?

A. 1.00 atm

B. 2.00 atm

Correct C. 3.00 atm

D. 4.00 atm

Correct Answer: C

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Question 11

The atomic radius of an element in a given period decreases as the atomic number increases. Which of the following elements has the largest atomic radius in period 3?

Correct A. Phosphorus

B. Sulfur

C. Chlorine

D. Argon

Correct Answer: A

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Question 12

A solution of sodium chloride (NaCl) is prepared by dissolving 35.5 g of NaCl in 100 mL of water. The resulting solution has a concentration of 3.55 M. What is the molarity of the solution if 25 mL of the solution is diluted to 250 mL?

A. 0.14 M

Correct B. 0.28 M

C. 0.35 M

D. 0.42 M

Correct Answer: B

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Question 13

The solubility of a subs\tance is defined as the maximum amount of the subs\tance that can dissolve in a given amount of solvent at a particular temperature. What is the term for the minimum amount of a subs\tance that must be present in a solution for the subs\tance to be considered soluble?

Correct A. Critical concentration

B. Saturation point

C. Solubility limit

D. Minimum solubility

Correct Answer: A

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Question 14

A reaction is said to be in equilibrium when the rates of the forward and reverse reactions are equal. What is the term for the equilibrium cons\tant that is used to describe the ratio of the concentrations of the products to the concentrations of the reac\tants?

Correct A. Equilibrium cons\tant (K)

B. Reaction quotient (Q)

C. Thermodynamic equilibrium cons\tant (K)

D. Dynamic equilibrium cons\tant (K)

Correct Answer: A

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Question 15

The pH of a solution is a measure of its acidity or basicity. What is the pH of a solution that has a hydrogen ion concentration of 1.0 x 10^-5 M?

A. 5.0

B. 6.0

Correct C. 7.0

D. 8.0

Correct Answer: C

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Question 16

Determine the pH of a 0.1 M solution of HCl at 25°C, given that the dissociation cons\tant of HCl is 10^\( -7 \) and the temperature dep\endence of the dissociation cons\tant is given by the equation: \log(K) = -0.5\( 1/T - 1/298.15 \) + 6.5.

Correct A. 2

B. 3

C. 4

D. 5

Correct Answer: A

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Question 17

A 2.5 L flask contains 0.5 mol of an ideal gas at 25°C. If 0.25 mol of the gas is removed, what is the new pressure of the gas in the flask?

A. 0.5 atm

Correct B. 0.75 atm

C. 1 atm

D. 1.5 atm

Correct Answer: B

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Question 18

A 0.1 M solution of NaOH is titrated with 0.1 M HCl. If 20 mL of HCl is added, what is the pH of the solution?

A. 2

Correct B. 3

C. 4

D. 5

Correct Answer: B

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Question 19

A 2.5 L flask contains 0.5 mol of an ideal gas at 25°C. If the gas is compressed to half its original volume, what is the new pressure of the gas in the flask?

A. 0.5 atm

B. 0.75 atm

Correct C. 1 atm

D. 1.5 atm

Correct Answer: C

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Question 20

A 0.1 M solution of HCl is titrated with 0.1 M NaOH. If 20 mL of NaOH is added, what is the pH of the solution?

A. 2

B. 3

C. 4

Correct D. 5

Correct Answer: D

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Question 21

The reaction of sodium hydroxide with acetic acid is an example of a reaction that exhibits which type of equilibrium?

A. Homogeneous equilibrium

B. Heterogeneous equilibrium

Correct C. Chemical equilibrium

D. Physical equilibrium

Correct Answer: C

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Question 22

A sample of a polymer has a molecular weight of 50000 g/mol. If the degree of polymerization is 200, what is the molar mass of the repeating unit?

A. 250 g/mol

Correct B. 500 g/mol

C. 750 g/mol

D. 1000 g/mol

Correct Answer: B

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Question 23

A solution of 0.1 M NaCl is prepared by dissolving 6.0 g of NaCl in 100 mL of water. What is the concentration of the solution in g/L?

A. 0.6 g/L

Correct B. 1.2 g/L

C. 1.8 g/L

D. 2.4 g/L

Correct Answer: B

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Question 24

The reaction of hydrogen gas with oxygen gas is an example of a reaction that exhibits which type of periodicity?

A. Periodicity of atomic radius

B. Periodicity of electronegativity

Correct C. Periodicity of ionization energy

D. Periodicity of electron affinity

Correct Answer: C

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Question 25

A sample of a polymer has a molecular weight of 50000 g/mol. If the degree of polymerization is 200, what is the molar mass of the repeating unit?

A. 250 g/mol

Correct B. 500 g/mol

C. 750 g/mol

D. 1000 g/mol

Correct Answer: B

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