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POST UTME OSUSTECH 2021 Chemistry | Objective

Are you preparing for POST UTME OSUSTECH exams? Reviewing past questions is one of the most effective ways to guarantee a high score. This practice hub features authentic 2021 Chemistry (Objective) questions designed to simulate the real exam environment.

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Question 1

Determine the rate cons\tant (k) for the reaction: 2NO(g) + O2(g) → 2NO2(g) at 298 K, given that the initial concentrations of NO and O2 are 0.1 M and 0.2 M, respectively, and the rate of reaction is 0.05 M/s after 10 minutes.

Correct A. \( 2.5 \times 10^{-3} , \text{s}^{-1} \)

B. \( 5.0 \times 10^{-3} , \text{s}^{-1} \)

C. \( 1.0 \times 10^{-2} , \text{s}^{-1} \)

D. \( 2.0 \times 10^{-2} , \text{s}^{-1} \)

Correct Answer: A

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Question 2

A 0.1 M solution of HCl is mixed with a 0.1 M solution of NaOH in a 1:1 ratio. What is the concentration of the resulting 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 diagram of a titration setup is shown below. If 25 mL of 0.1 M HCl is added to 25 mL of 0.1 M NaOH, what is the pH of the resulting solution?

A. 7

Correct B. 8

C. 9

D. 10

Correct Answer: B

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Question 4

A 1.0 M solution of NH3 is mixed with a 1.0 M solution of HCl in a 1:1 ratio. What is the concentration of the resulting solution?

A. 0.5 M

Correct B. 1.0 M

C. 1.5 M

D. 2.0 M

Correct Answer: B

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Question 5

A diagram of a chromatography setup is shown below. If a 1.0 M solution of C6H12O6 is separated u\sing a 1.0 M solution of H2O, what is the Rf value of the resulting solution?

A. 0.2

B. 0.4

Correct C. 0.6

D. 0.8

Correct Answer: C

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Question 6

A 0.500 g sample of a metal oxide is heated in a crucible until it decomposes completely. The mass of the metal obtained is 0.350 g. If the metal oxide has a molar mass of 120 g/mol and the metal has a molar mass of 40 g/mol, calculate the percentage yield of the metal.

Correct A. 80%

B. 85%

C. 90%

D. 95%

Correct Answer: A

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Question 7

The rate cons\tant (k) for a first-order reaction is 0.050 min^-1. If the initial concentration of the reac\tant is 0.200 M, calculate the concentration of the reac\tant after 10 minutes.

Correct A. 0.100 M

B. 0.150 M

C. 0.200 M

D. 0.250 M

Correct Answer: A

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Question 8

A 2.00 L sample of a gas at 25°C and 1.00 atm is collected over water at 25°C. If the vapor pressure of water at 25°C is 0.0313 atm, calculate the partial pressure of the gas.

Correct A. 0.968 atm

B. 0.980 atm

C. 0.992 atm

D. 1.00 atm

Correct Answer: A

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Question 9

A 1.00 g sample of a hydrocarbon is burned in a bomb calorimeter, relea\sing 2.50 kJ of heat. If the molar mass of the hydrocarbon is 120 g/mol, calculate the heat of combustion per mole of the hydrocarbon.

Correct A. -21.7 kJ/mol

B. -22.1 kJ/mol

C. -22.5 kJ/mol

D. -23.0 kJ/mol

Correct Answer: A

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Question 10

A 0.500 M solution of a weak acid (HA) is 10.0% ionized at 25°C. If the dissociation cons\tant (Ka) of the acid is 1.0 x 10^-5, calculate the pH of the solution.

A. 2.00

Correct B. 2.30

C. 2.50

D. 3.00

Correct Answer: B

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Question 11

Determine the pH of a 0.1 M solution of HCl.

A. 1

B. 2

C. 3

Correct D. 4

Correct Answer: D

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Question 12

Calculate the molarity of a solution containing 25 g of NaOH in 250 mL of water.

A. 0.1 M

B. 0.5 M

Correct C. 1 M

D. 2 M

Correct Answer: C

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Question 13

Identify the type of reaction represented by the equation: \( 2Na + Cl_2 \rightarrow 2NaCl \).

A. Synthesis reaction

B. Decomposition reaction

Correct C. Single displacement reaction

D. Double displacement reaction

Correct Answer: C

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Question 14

A 2.5 L flask contains 0.5 mol of an ideal gas at 27°C. Calculate the pressure of the gas u\sing the ideal gas law.

A. 1 atm

Correct B. 2 atm

C. 3 atm

D. 4 atm

Correct Answer: B

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Question 15

Determine the concentration of a solution containing 3.2 g of glu\cose in 250 mL of water.

A. 0.1 M

B. 0.5 M

Correct C. 1 M

D. 2 M

Correct Answer: C

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Question 16

Determine the number of moles of CO2 produced when 2.5 g of C6H12O6 is completely oxidized in the presence of excess O2, given that the balanced equation for the reaction is: C6H12O6 + 6O2 → 6CO2 + 6H2O.

A. 0.05 mol

Correct B. 0.1 mol

C. 0.15 mol

D. 0.2 mol

Correct Answer: B

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Question 17

A sample of a polymer has a molecular weight of 50000 g/mol. If 0.5 g of the polymer is dissolved in 100 mL of solvent, what is the concentration of the solution in g/L?

A. 0.05 g/L

B. 0.5 g/L

Correct C. 5 g/L

D. 50 g/L

Correct Answer: C

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Question 18

The half-life of a radioactive subs\tance is 10 years. If 100 g of the subs\tance is initially present, how much of the subs\tance will remain after 30 years?

A. 10 g

Correct B. 20 g

C. 30 g

D. 40 g

Correct Answer: B

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Question 19

A solution of HCl is 0.1 M. If 20 mL of the solution is diluted to 100 mL, what is the concentration of the resulting solution?

A. 0.05 M

B. 0.1 M

Correct C. 0.15 M

D. 0.2 M

Correct Answer: C

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Question 20

A sample of a gas has a volume of 2 L at a pressure of 1 atm. If the pressure is increased to 2 atm, what is the new volume of the gas?

A. 1 L

B. 2 L

Correct C. 4 L

D. 8 L

Correct Answer: C

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Question 21

At 25°C, 1.00 L of an ideal gas at 2.00 atm exerts a pressure of 2.00 atm. What is the volume of the gas at 4.00 atm and 25°C?

Correct A. 0.500 L

B. 1.00 L

C. 2.00 L

D. 4.00 L

Correct Answer: A

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Question 22

A solution contains 0.100 M HCl and 0.100 M NaOH. What is the pH of the solution after mixing 50.0 mL of each solution?

A. 0.00

Correct B. 1.00

C. 2.00

D. 3.00

Correct Answer: B

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Question 23

A sample of a polymer has a molecular weight of 100,000 g/mol. If 0.500 g of the polymer is dissolved in 100.0 mL of solvent, what is the concentration of the solution in g/L?

A. 0.500 g/L

B. 1.00 g/L

C. 2.00 g/L

Correct D. 5.00 g/L

Correct Answer: D

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Question 24

A reaction is represented by the equation: 2A + B → C + 2D. If 1.00 mol of A and 0.500 mol of B are present, what is the limiting reac\tant?

A. A

Correct B. B

C. C

D. D

Correct Answer: B

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Question 25

A solution contains 0.100 M HCl and 0.100 M NaOH. What is the pH of the solution after mixing 50.0 mL of each solution?

A. 0.00

Correct B. 1.00

C. 2.00

D. 3.00

Correct Answer: B

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