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POST UTME BELLS UNIVERSITY 2023 Chemistry | Objective

Are you preparing for POST UTME BELLS UNIVERSITY 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.

Practice these randomly selected questions to test your readiness.

Question 1

Determine the solubility of $\text{CaF}_2$ in a solution containing $0.1\,\text{M}$ $\text{HF}$ at $25\,\text{°C}$, given that $K_{sp} = 3.9\times 10^{-11}$ and $K_{f} = 3.5\times 10^{-3}$ for $\text{HF}$.

A. $1.2\times 10^{-4}\,\text{M}$

Correct B. $2.5\times 10^{-4}\,\text{M}$

C. $4.8\times 10^{-4}\,\text{M}$

D. $6.2\times 10^{-4}\,\text{M}$

Correct Answer: B

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Question 2

A $1.0\,\text{L}$ solution of $\text{NaOH}$ contains $0.15\,\text{M}$ $\text{NaOH}$. If $10\,\text{mL}$ of this solution is added to $100\,\text{mL}$ of $0.10\,\text{M}$ $\text{HCl}$, what is the concentration of $\text{OH}^{-}$ in the resulting solution?

A. $0.015\,\text{M}$

Correct B. $0.030\,\text{M}$

C. $0.045\,\text{M}$

D. $0.060\,\text{M}$

Correct Answer: B

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Question 3

The diagram below shows a titration setup for determining the concentration of a $\text{Ca(OH)}_2$ solution. If $25.0\,\text{mL}$ of $0.10\,\text{M}$ $\text{HCl}$ is required to reach the equivalence point, what is the concentration of the $\text{Ca(OH)}_2$ solution?

A. $0.025\,\text{M}$

B. $0.050\,\text{M}$

C. $0.075\,\text{M}$

Correct D. $0.100\,\text{M}$

Correct Answer: D

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Question 4

A $2.0\,\text{g}$ sample of a polymer is dissolved in $100\,\text{mL}$ of $\text{THF}$. If the polymer has a molecular weight of $10^5\,\text{g/mol}$, what is the concentration of the polymer solution in $\text{g/L}$?

A. $2.0\times 10^{-3}\,\text{g/L}$

B. $4.0\times 10^{-3}\,\text{g/L}$

C. $6.0\times 10^{-3}\,\text{g/L}$

Correct D. $8.0\times 10^{-3}\,\text{g/L}$

Correct Answer: D

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Question 5

The diagram below shows a setup for determining the rate cons\tant of a reaction. If the reaction is first-order with respect to the reac\tant, what is the relationship between the rate cons\tant and the slope of the plot?

Correct A. $k = \text{slope}$

B. $k = \frac{1}{\text{slope}}$

C. $k = \text{slope}^2$

D. $k = \frac{1}{\text{slope}^2}$

Correct Answer: A

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Question 6

Determine the number of moles of sulfur dioxide gas (SO2) produced when 2.5 moles of sulfur trioxide gas (SO3) react with excess oxygen gas (O2) according to the equation: 2SO3 + O2 → 2SO2 + O.

Correct A. 1.25 moles

B. 2.5 moles

C. 3.75 moles

D. 5 moles

Correct Answer: A

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Question 7

A 25.0 mL sample of a solution containing 0.100 M sodium hydroxide (NaOH) is titrated with 0.0500 M hydrochloric acid (HCl). Calculate the volume of HCl required to reach the equivalence point.

A. 12.5 mL

Correct B. 25.0 mL

C. 37.5 mL

D. 50.0 mL

Correct Answer: B

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Question 8

A diagram of a redox reaction is shown below. Identify the oxidizing agent.

A. Cell A

Correct B. Cell B

C. Both cells

D. Neither cell

Correct Answer: B

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Question 9

A 10.0 g sample of a mixture containing 80.0% sodium chloride (NaCl) and 20.0% water (H2O) is heated to produce sodium hydroxide (NaOH) and hydrogen chloride (HCl). Calculate the mass of NaOH produced.

Correct A. 2.50 g

B. 5.00 g

C. 7.50 g

D. 10.0 g

Correct Answer: A

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Question 10

A diagram of a electrolysis cell is shown below. Identify the product formed at the cathode.

Correct A. H2

B. O2

C. Na

D. Cl2

Correct Answer: A

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Question 11

The rate cons\tant (k) for a first-order reaction is given by the equation: k = 2.303/t \log10$ A0/A $. If the initial concentration (A0) is 0.1 M and the concentration after 10 minutes (A) is 0.05 M, what is the value of k?

A. 0.0005 min^-1

B. 0.001 min^-1

Correct C. 0.005 min^-1

D. 0.01 min^-1

Correct Answer: C

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Question 12

A solution containing 0.1 M NH3 is mixed with 0.1 M HCl. 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 13

The diagram below shows a titration setup. What is the purpose of the burette?

Correct A. To measure the volume of the titrant

B. To measure the volume of the analyte

C. To mix the titrant and analyte

D. To measure the pH of the solution

Correct Answer: A

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Question 14

A sample of polystyrene has a molecular weight of 100,000 g/mol. What is the number of monomer units in the polymer chain?

A. 100

B. 1000

C. 10,000

Correct D. 100,000

Correct Answer: D

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Question 15

The diagram below shows a molecule of benzene. What is the type of bond between the carbon atoms?

A. Sigma bond

Correct B. Pi bond

C. Delta bond

D. Gamma bond

Correct Answer: B

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Question 16

A 2.50-g sample of a compound containing only carbon and hydrogen is found to have a mass of 2.00 g when heated in a stream of oxygen gas. The mass of the carbon dioxide produced is 3.75 g. Calculate the empirical formula of the compound.

A. CH2

Correct B. C2H4

C. C3H6

D. C4H8

Correct Answer: B

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Question 17

The s\tandard enthalpy of formation of CO2(g) is -393.5 kJ/mol. The s\tandard enthalpy of formation of H2O(l) is -285.8 kJ/mol. Calculate the s\tandard enthalpy of formation of CH4(g).

Correct A. -74.8 kJ/mol

B. -74.5 kJ/mol

C. -74.2 kJ/mol

D. -75.1 kJ/mol

Correct Answer: A

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Question 18

A 10.0-mL sample of a solution containing 0.100 M NaCl is mixed with 20.0 mL of a solution containing 0.0500 M K2SO4. What is the concentration of Cl- ions in the resulting solution?

A. 0.0250 M

B. 0.0500 M

Correct C. 0.0750 M

D. 0.100 M

Correct Answer: C

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Question 19

A 25.0-g sample of a solid is found to have a mass of 20.0 g when heated in a stream of oxygen gas. The mass of the carbon dioxide produced is 5.00 g. What is the empirical formula of the compound?

A. C2H4

Correct B. C3H6

C. C4H8

D. C5H10

Correct Answer: B

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Question 20

The s\tandard enthalpy of formation of NH3(g) is -45.9 kJ/mol. The s\tandard enthalpy of formation of H2O(l) is -285.8 kJ/mol. Calculate the s\tandard enthalpy of formation of NH4Cl(s).

Correct A. -206.5 kJ/mol

B. -206.2 kJ/mol

C. -206.9 kJ/mol

D. -207.1 kJ/mol

Correct Answer: A

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Question 21

A 5.00-mL sample of a solution containing 0.100 M NaOH is mixed with 10.0 mL of a solution containing 0.0500 M HCl. What is the concentration of OH- ions in the resulting solution?

A. 0.0250 M

B. 0.0500 M

Correct C. 0.0750 M

D. 0.100 M

Correct Answer: C

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Question 22

A 10.0-mL sample of a solution containing 0.100 M K2SO4 is mixed with 20.0 mL of a solution containing 0.0500 M NaCl. What is the concentration of Cl- ions in the resulting solution?

A. 0.0250 M

B. 0.0500 M

Correct C. 0.0750 M

D. 0.100 M

Correct Answer: C

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Question 23

A 25.0-g sample of a solid is found to have a mass of 20.0 g when heated in a stream of oxygen gas. The mass of the carbon dioxide produced is 5.00 g. What is the empirical formula of the compound?

A. C2H4

Correct B. C3H6

C. C4H8

D. C5H10

Correct Answer: B

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Question 24

Calculate the s\tandard enthalpy of formation of CO2(g) from the following data: ΔHf(CO2(g)) = -393.5 kJ/mol, ΔHf(C(g)) = 110.5 kJ/mol, ΔHf(O2(g)) = 0 kJ/mol.

A. -393.5 kJ/mol

B. -393.5 kJ/mol + 110.5 kJ/mol

C. -393.5 kJ/mol - 110.5 kJ/mol

Correct D. -393.5 kJ/mol + 110.5 kJ/mol + 0 kJ/mol

Correct Answer: D

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Question 25

A polymer has a molecular weight of 100,000 g/mol. If the polymer is composed of 80% monomer A and 20% monomer B, what is the molecular weight of monomer A?

Correct A. 80,000 g/mol

B. 100,000 g/mol

C. 120,000 g/mol

D. 140,000 g/mol

Correct Answer: A

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