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POST UTME CRAWFORD UNIVERSITY 2022 Chemistry | Objective

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Question 1

A 0.1 M solution of a weak acid HA is titrated with 0.1 M NaOH. At the equivalence point, the pH of the solution is 7. What is the pKa of the acid?

A. 3.5

B. 4.5

Correct C. 5.5

D. 6.5

Correct Answer: C

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Question 2

A polymer has a molecular weight of 100,000 g/mol. If 1 g of the polymer is dissolved in 100 mL of water, what is the concentration of the solution in g/L?

A. 1 g/L

B. 10 g/L

Correct C. 100 g/L

D. 1000 g/L

Correct Answer: C

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Question 3

A metal M has a s\tandard reduction potential of -0.5 V. If a cell is constructed with M as the anode and Zn as the cathode, what is the s\tandard cell potential?

A. -1.0 V

Correct B. -0.5 V

C. 0.0 V

D. 1.0 V

Correct Answer: B

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Question 4

A 1.0 M solution of HCl is titrated with 1.0 M NaOH. If 20 mL of NaOH is added, what is the pH of the solution?

A. 1

B. 2

Correct C. 3

D. 4

Correct Answer: C

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Question 5

A reaction has a rate cons\tant of 2.0 s^-1. If the initial concentration of the reac\tant is 1.0 M, what is the concentration after 10 minutes?

A. 0.1 M

Correct B. 0.5 M

C. 1.0 M

D. 2.0 M

Correct Answer: B

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Question 6

Determine the pH of a 0.1 M solution of HCl. The dissociation cons\tant (Ka) for HCl is 10^\( -7 \).

A. 1

B. 2

C. 3

Correct D. 4

Correct Answer: D

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Question 7

A metal M reacts with chlorine gas to form a white solid. The reaction is as follows: M + Cl2 → MCl2. If 2.5 g of MCl2 is obtained from 2.5 g of M, calculate the percentage yield of MCl2.

A. 50%

B. 60%

Correct C. 70%

D. 80%

Correct Answer: C

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Question 8

A solution contains 0.1 M HCl and 0.1 M NaOH. What is the pH of the solution after 10 mL of 1 M HCl is added?

A. 1

Correct B. 2

C. 3

D. 4

Correct Answer: B

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Question 9

A 0.1 M solution of H2SO4 is titrated with 0.1 M NaOH. What is the pH of the solution after 20 mL of NaOH has been added?

A. 1

B. 2

C. 3

Correct D. 4

Correct Answer: D

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Question 10

A metal M reacts with oxygen to form a white solid. The reaction is as follows: 4M + 3O2 → 2M2O3. If 2.5 g of M2O3 is obtained from 2.5 g of M, calculate the percentage yield of M2O3.

A. 50%

B. 60%

Correct C. 70%

D. 80%

Correct Answer: C

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Question 11

A 0.1 M solution of a weak acid HA is mixed with 0.1 M solution of a strong base NaOH. If the initial pH of the acid solution is 3, calculate the pH of the resulting solution after the reaction is complete.

A. 2

Correct B. 4

C. 6

D. 8

Correct Answer: B

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Question 12

A sample of a gas at 25°C and 1 atm is compressed to 2 atm. If the initial volume is 2 L, calculate the final 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 13

A solution contains 0.1 M NaCl and 0.1 M CaCl2. If 10 mL of 1 M HCl is added to 90 mL of the solution, what is the concentration of Cl- ions in 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 14

A 1 M solution of a weak base B is mixed with 1 M solution of a strong acid HCl. If the initial pH of the base solution is 10, calculate the pH of the resulting solution after the reaction is complete.

A. 4

B. 6

Correct C. 8

D. 10

Correct Answer: C

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Question 15

A sample of a gas at 50°C and 2 atm is expanded to 1 atm. If the initial volume is 5 L, calculate the final volume of the gas.

A. 2 L

Correct B. 5 L

C. 10 L

D. 20 L

Correct Answer: B

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Question 16

Determine the pH of a 0.1 M solution of HCl, given that the solubility product cons\tant (Ksp) of CaF2 is 3.9 x 10^-11.

A. 1

B. 2

C. 3

Correct D. 4

Correct Answer: D

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Question 17

A 2.5 g sample of a metal carbonate is heated strongly. If 1.2 g of CO2 is produced, calculate the percentage purity of the carbonate.

A. 80%

B. 85%

Correct C. 90%

D. 95%

Correct Answer: C

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Question 18

A 25 mL sample of 0.1 M H2SO4 is titrated with 0.1 M NaOH. Calculate the volume of NaOH required to reach the equivalence point.

A. 25 mL

B. 50 mL

C. 75 mL

Correct D. 100 mL

Correct Answer: D

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Question 19

A solution contains 0.1 M HCl and 0.1 M NaOH. Calculate the pH of the solution after 50 mL of 0.1 M HCl is added to 50 mL of 0.1 M NaOH.

A. 1

B. 2

C. 3

Correct D. 4

Correct Answer: D

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Question 20

A 2.5 g sample of a metal carbonate is heated strongly. If 1.2 g of CO2 is produced, calculate the percentage purity of the carbonate.

A. 80%

B. 85%

Correct C. 90%

D. 95%

Correct Answer: C

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Question 21

Determine the s\tandard enthalpy of formation of CO2(g) from the following data: ΔH°(C(s) + O2(g) → CO2(g)) = -393.5 kJ/mol and ΔH°(H2(g) + 1/2O2(g) → H2O(l)) = -285.8 kJ/mol.

Correct A. -677.3 kJ/mol

B. -677.3 kJ/mol

C. -677.3 kJ/mol

D. -677.3 kJ/mol

Correct Answer: A

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Question 22

A sample of H2(g) is collected over water at 25°C and 1 atm. If the partial pressure of H2(g) is 0.75 atm, what is the mole \fraction of H2(g) in the vapor phase?

Correct A. 0.75

B. 0.75

C. 0.75

D. 0.75

Correct Answer: A

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Question 23

The reaction 2NO(g) + O2(g) → 2NO2(g) has a rate cons\tant of 1.5 × 10^\( -3 \) s^\( -1 \) at 298 K. What is the rate of reaction if the initial concentrations of NO(g) and O2(g) are 0.10 M and 0.20 M, respectively?

Correct A. 1.8 × 10^\( -4 \) M s^\( -1 \)

B. 1.8 × 10^\( -4 \) M s^\( -1 \)

C. 1.8 × 10^\( -4 \) M s^\( -1 \)

D. 1.8 × 10^\( -4 \) M s^\( -1 \)

Correct Answer: A

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Question 24

A 2.50-g sample of an unknown hydrocarbon is burned in a bomb calorimeter, producing 12.5 kJ of heat. If the heat of combustion of C(s) is -393.5 kJ/mol and the heat of combustion of H2(g) is -285.8 kJ/mol, what is the empirical formula of the hydrocarbon?

Correct A. C2H4

B. C2H4

C. C2H4

D. C2H4

Correct Answer: A

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Question 25

A 1.00-L flask contains 0.0500 M H2(g) and 0.0500 M I2(g) at 298 K. What is the equilibrium cons\tant for the reaction H2(g) + I2(g) ⇌ 2HI(g)?

Correct A. 1.8 × 10^\( -3 \)

B. 1.8 × 10^\( -3 \)

C. 1.8 × 10^\( -3 \)

D. 1.8 × 10^\( -3 \)

Correct Answer: A

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