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POST UTME DELSU 2023 Chemistry | Objective

Are you preparing for POST UTME DELSU exams? Reviewing past questions is one of the most effective ways to guarantee a high score. This practice hub features authentic 2023 Chemistry (Objective) questions designed to simulate the real exam environment.

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Question 1

Determine the rate cons\tant (k) for the first-order reaction: A → B, given that the initial concentration of A is 0.1 M and the concentration of A after 2 minutes is 0.05 M.

Correct A. \( k = \frac{2.303}{t} \log \frac{[A]_0}{[A]_t} \)

B. \( k = \frac{[A]_t}{[A]_0} \)

C. \( k = \frac{t}{[A]_0} \)

D. \( k = \frac{2.303}{t} \log \frac{[A]_t}{[A]_0} \)

Correct Answer: A

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Question 2

A sample of 2.5 g of sodium hydroxide (NaOH) is dissolved in 100 mL of water. Calculate the molarity of the solution.

A. 0.1 M

Correct B. 0.2 M

C. 0.3 M

D. 0.4 M

Correct Answer: B

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Question 3

A 2.5 M solution of hydrochloric acid (HCl) is titrated with a 2.5 M solution of sodium hydroxide (NaOH). Calculate the volume of NaOH required to neutralize 25 mL of HCl.

A. 12.5 mL

Correct B. 25 mL

C. 37.5 mL

D. 50 mL

Correct Answer: B

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Question 4

A 2.5 M solution of sodium hydroxide (NaOH) is titrated with a 2.5 M solution of hydrochloric acid (HCl). Calculate the volume of HCl required to neutralize 25 mL of NaOH.

A. 12.5 mL

Correct B. 25 mL

C. 37.5 mL

D. 50 mL

Correct Answer: B

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Question 5

A 2.5 M solution of sodium hydroxide (NaOH) is titrated with a 2.5 M solution of hydrochloric acid (HCl). Calculate the pH of the solution after 25 mL of HCl has been added.

A. 7

Correct B. 8

C. 9

D. 10

Correct Answer: B

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Question 6

Determine the number of moles of electrons transferred in the reaction: Zn(s) + Cu2+(aq) → Zn2+(aq) + Cu(s). Given that 2.5 g of Zn is used and the reaction occurs at 25°C.

A. 1 mole

Correct B. 2 moles

C. 3 moles

D. 4 moles

Correct Answer: B

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Question 7

A 0.1 M solution of NaOH is prepared by dissolving 4 g of NaOH in 100 mL of water. What is the concentration of the solution in g/L?

A. 0.4 g/L

B. 0.8 g/L

C. 1.2 g/L

Correct D. 1.6 g/L

Correct Answer: D

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Question 8

The half-life of a radioactive subs\tance is 5 years. If 100 g of the subs\tance is present initially, how much will remain after 10 years?

A. 50 g

B. 25 g

C. 12.5 g

Correct D. 6.25 g

Correct Answer: D

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Question 9

A solution containing 10 g of glu\cose (C6H12O6) is prepared by dissolving the glu\cose in 100 mL of water. What is the concentration of the solution in g/L?

A. 10 g/L

B. 20 g/L

C. 30 g/L

Correct D. 40 g/L

Correct Answer: D

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Question 10

A 0.1 M solution of HCl is prepared by dissolving 2 g of HCl in 100 mL of water. What is the concentration of the solution in g/L?

A. 0.2 g/L

B. 0.4 g/L

C. 0.6 g/L

Correct D. 0.8 g/L

Correct Answer: D

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Question 11

The atomic radius of an element is 100 pm. If the element is in its ground state, what is the expected value of its atomic radius in the excited state?

Correct A. 110 pm

B. 90 pm

C. 120 pm

D. 130 pm

Correct Answer: A

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Question 12

A metal oxide has the formula MO2. If the metal has an oxidation state of +2, what is the charge on the oxide ion?

Correct A. -2

B. +2

C. -4

D. +4

Correct Answer: A

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Question 13

A solution of NaCl is prepared by dissolving 35.5 g of NaCl in 250 mL of water. What is the molarity of the solution?

A. 0.1 M

Correct B. 0.2 M

C. 0.3 M

D. 0.4 M

Correct Answer: B

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Question 14

A gas has a volume of 2.5 L at a pressure of 1.5 atm. What is the volume of the gas at a pressure of 3.0 atm?

Correct A. 1.5 L

B. 2.0 L

C. 2.5 L

D. 3.0 L

Correct Answer: A

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Question 15

A metal has a s\tandard enthalpy of formation of -200 kJ/mol. What is the s\tandard enthalpy of combustion of the metal?

A. -100 kJ/mol

B. -150 kJ/mol

Correct C. -200 kJ/mol

D. -250 kJ/mol

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 described by the equation \( \log_{10} K_a = -\frac{1000}{4.57} left\( \frac{1}{T} - \frac{1}{298} \right \ \) ).

A. 1

B. 2

C. 3

Correct D. 4

Correct Answer: D

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Question 17

A 25 mL sample of 0.5 M HCl is titrated with 0.5 M NaOH. Calculate the volume of NaOH required to reach the equivalence point.

A. 10 mL

Correct B. 20 mL

C. 25 mL

D. 30 mL

Correct Answer: B

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Question 18

The s\tandard enthalpy of formation of CO2(g) is -393.5 kJ/mol. Calculate the s\tandard enthalpy of combustion of 1 mole of methane (CH4(g)) at 298 K.

Correct A. -890 kJ/mol

B. -890.5 kJ/mol

C. -891 kJ/mol

D. -891.5 kJ/mol

Correct Answer: A

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Question 19

The boiling point of a solution containing 10 g of glu\cose (C6H12O6) in 100 g of water is 101.5°C. Calculate the molality of the solution.

A. 0.5 m

Correct B. 0.7 m

C. 0.9 m

D. 1.1 m

Correct Answer: B

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Question 20

A 0.1 M solution of NaOH is titrated with 0.1 M HCl. Calculate the pH of the solution after 20 mL of HCl has been added.

A. 1

B. 2

C. 3

Correct D. 4

Correct Answer: D

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