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POST UTME ESUT 2023 Chemistry | Objective

Are you preparing for POST UTME ESUT 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 number of moles of CO2 produced from the combustion of 2.5 g of glu\cose (C6H12O6) in the presence of excess oxygen.

A. 0.25 mol

B. 0.5 mol

Correct C. 1.0 mol

D. 1.25 mol

Correct Answer: C

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Question 2

A 0.5 M solution of HCl is mixed with a 0.5 M solution of NaOH. What is the pH of the resulting solution?

A. 1

Correct B. 2

C. 3

D. 4

Correct Answer: B

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Question 3

A diagram of a titration setup is shown below. If 25 mL of 0.1 M NaOH is required to reach the equivalence point, what is the concentration of the HCl solution?

A. 0.05 M

Correct B. 0.1 M

C. 0.2 M

D. 0.5 M

Correct Answer: B

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Question 4

The s\tandard enthalpy of formation of CO2(g) is -393.5 kJ/mol. What is the s\tandard enthalpy of formation of glu\cose (C6H12O6(s))?

A. -2800 kJ/mol

B. -2900 kJ/mol

Correct C. -3000 kJ/mol

D. -3100 kJ/mol

Correct Answer: C

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Question 5

A diagram of a gas collection apparatus is shown below. If 250 mL of gas is collected at a pressure of 750 mmHg and a temperature of 25°C, what is the volume of the gas at STP?

A. 1.0 L

B. 1.5 L

Correct C. 2.0 L

D. 2.5 L

Correct Answer: C

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Question 6

A sample of a non-metallic oxide, X2O3, has a molar mass of 144 g/mol. If the oxide is 80% oxygen by mass, what is the molar mass of element X?

A. 72 g/mol

B. 80 g/mol

Correct C. 96 g/mol

D. 112 g/mol

Correct Answer: C

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Question 7

A solution of HCl is titrated with a solution of NaOH. The initial pH of the HCl solution is 2. If 25 mL of the NaOH solution is added, the pH of the solution increases to 3. What is the concentration of the NaOH 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 8

A reaction is represented by the equation: 2A + B → 2C + D. If the rate of disappearance of A is 0.05 mol/L·s and the rate of appearance of C is 0.02 mol/L·s, what is the rate of appearance of D?

A. 0.01 mol/L·s

Correct B. 0.02 mol/L·s

C. 0.03 mol/L·s

D. 0.04 mol/L·s

Correct Answer: B

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Question 9

A solution of H2SO4 is electrolyzed u\sing a platinum electrode. If the current is 5 A and the time is 10 min, what is the mass of H2 gas produced?

A. 0.5 g

B. 1 g

Correct C. 1.5 g

D. 2 g

Correct Answer: C

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Question 10

A sample of a non-metallic oxide, X2O3, has a molar mass of 144 g/mol. If the oxide is 80% oxygen by mass, what is the molar mass of element X?

A. 72 g/mol

B. 80 g/mol

Correct C. 96 g/mol

D. 112 g/mol

Correct Answer: C

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Question 11

Determine the rate cons\tant (k) for the reaction: 2NO(g) + O2(g) → 2NO2(g), given that the initial concentrations of NO and O2 are 0.5 M and 0.2 M, respectively, and the rate of reaction is 0.02 M/s after 10 minutes.

A. \( k = \frac{2.303}{t} \log \frac{[NO]_0 [O_2]_0}{[NO_2]_t} \)

B. \( k = \frac{2.303}{t} \log \frac{[NO_2]_t}{[NO]_0 [O_2]_0} \)

Correct C. \( k = \frac{2.303}{t} \log \frac{[NO]_0 [O_2]_0}{[NO_2]_t} \)

D. \( k = \frac{2.303}{t} \log \frac{[NO_2]_t}{[NO]_0 [O_2]_0} \)

Correct Answer: C

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Question 12

A 2.5 L flask contains 0.5 mol of an ideal gas at 298 K. Calculate the work done (w) by the gas when it expands to 3.5 L against a cons\tant external pressure of 0.5 atm.

Correct A. \( w = -nRT ln \frac{V_2}{V_1} \)

B. \( w = nRT ln \frac{V_2}{V_1} \)

C. \( w = -nRT ln \frac{V_1}{V_2} \)

D. \( w = nRT ln \frac{V_1}{V_2} \)

Correct Answer: A

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Question 13

A solution containing 0.1 M Fe2+ ions is mixed with a solution containing 0.1 M SCN- ions. Calculate the concentration of the complex ion [Fe(SCN)6]4- formed after the reaction is complete.

A. \( K = \frac{[Fe\( SCN \ \)_6]^{4-}}{[Fe^{2+}] [SCN^-]^6} )

B. \( K = \frac{[Fe\( SCN \ \)_6]^{4-}}{[Fe^{2+}] [SCN^-]^3} )

Correct C. \( K = \frac{[Fe\( SCN \ \)_6]^{4-}}{[Fe^{2+}] [SCN^-]^2} )

D. \( K = \frac{[Fe\( SCN \ \)_6]^{4-}}{[Fe^{2+}] [SCN^-]^5} )

Correct Answer: C

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Question 14

A 1.0 M solution of NaOH is mixed with a 1.0 M solution of HCl. Calculate the pH of the resulting solution.

Correct A. \( pH = \frac{1}{2} \( pOH + 14 \ \) )

B. \( pH = \frac{1}{2} \( pH + 14 \ \) )

C. \( pH = \frac{1}{2} \( pOH - 14 \ \) )

D. \( pH = \frac{1}{2} \( pH - 14 \ \) )

Correct Answer: A

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Question 15

A 2.0 M solution of H2SO4 is mixed with a 2.0 M solution of NaOH. Calculate the concentration of the resulting solution.

A. \( [H_2SO_4] = 1.0 M \)

B. \( [NaOH] = 1.0 M \)

Correct C. \( [H_2SO_4] = 0.5 M \)

D. \( [NaOH] = 0.5 M \)

Correct Answer: C

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Question 16

In a batch reactor, the rate of reaction is given by the equation: r = k[A]^2[B]. If the initial concentrations of [A] and [B] are 0.5 M and 0.2 M, respectively, and the reaction is carried out at 25°C, calculate the rate of reaction after 2 hours, given that the rate cons\tant k is 0.05 M^\( -1 \)s^\( -1 \).

A. 0.001 M/s

B. 0.005 M/s

Correct C. 0.01 M/s

D. 0.02 M/s

Correct Answer: C

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Question 17

A polymer has a molecular weight of 50000 g/mol and a degree of polymerization of 200. Calculate 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 18

A gas at 25°C and 1 atm is compressed to 5 atm. Calculate the new volume of the gas, given that the initial volume is 10 L.

A. 2 L

Correct B. 5 L

C. 10 L

D. 20 L

Correct Answer: B

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Question 19

A metal has a density of 8 g/cm^3 and a volume of 10 cm^3. Calculate the mass of the metal.

Correct A. 80 g

B. 100 g

C. 120 g

D. 140 g

Correct Answer: A

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Question 20

A solution contains 2 M NaOH and 1 M HCl. Calculate the pH of the solution.

A. 1

Correct B. 2

C. 3

D. 4

Correct Answer: B

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Question 21

A 0.5 M solution of HCl is titrated with 0.5 M NaOH. If 25 mL of HCl is required to reach the equivalence point, what is the volume of NaOH required to reach the equivalence point?

A. 12.5 mL

Correct B. 25 mL

C. 37.5 mL

D. 50 mL

Correct Answer: B

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Question 22

A polymer has a molecular weight of 100,000 g/mol and a degree of polymerization of 500. What is the molar mass of the repeating unit?

A. 200 g/mol

B. 400 g/mol

Correct C. 500 g/mol

D. 1000 g/mol

Correct Answer: C

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Question 23

A solution contains 0.1 M HCl and 0.1 M NaOH. What is the pH of the solution?

A. 1

B. 2

Correct C. 3

D. 4

Correct Answer: C

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Question 24

A metal has a density of 8 g/cm^3 and a volume of 10 cm^3. What is the mass of the metal?

A. 80 g

Correct B. 100 g

C. 120 g

D. 140 g

Correct Answer: B

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Question 25

A gas has a pressure of 2 atm and a volume of 10 L. If the temperature is increased to 300 K, what is the new volume?

A. 10 L

B. 20 L

Correct C. 30 L

D. 40 L

Correct Answer: C

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