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POST UTME MOUNTAIN TOP UNIVERSITY 2017 Chemistry | Objective

Are you preparing for POST UTME MOUNTAIN TOP UNIVERSITY exams? Reviewing past questions is one of the most effective ways to guarantee a high score. This practice hub features authentic 2017 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), 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.

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 2

A 25.0 mL sample of 0.100 M HCl is titrated with 0.100 M NaOH. Calculate the pH of the solution after 25.0 mL of NaOH has been added.

Correct A. \( pH = -\log[H^+] \)

B. \( pH = -\log[OH^-] \)

C. \( pH = \log \frac{[H^+]}{[OH^-]} \)

D. \( pH = \log \frac{[OH^-]}{[H^+]} \)

Correct Answer: A

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Question 3

A gas at 25°C and 1 atm is compressed to 4 atm. Calculate the new volume of the gas.

Correct A. \( V_1 P_1 = V_2 P_2 \)

B. \( \frac{P_1 V_1}{T_1} = \frac{P_2 V_2}{T_2} \)

C. \( \frac{P_1 V_1}{T_1} = \frac{P_2 V_2}{T_2} \)

D. \( \frac{P_1 V_1}{T_1} = \frac{P_2 V_2}{T_2} \)

Correct Answer: A

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Question 4

A 2.0 g sample of a subs\tance is burned in a bomb calorimeter, relea\sing 12.0 kJ of heat. Calculate the molar heat of combustion of the subs\tance.

Correct A. \( Delta H = \frac{Q}{n} \)

B. \( Delta H = \frac{Q}{m} \)

C. \( Delta H = \frac{Q}{V} \)

D. \( Delta H = \frac{Q}{T} \)

Correct Answer: A

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Question 5

A 1.0 M solution of NaOH is titrated with a 1.0 M solution of HCl. Calculate the pH of the solution after 50.0 mL of HCl has been added.

Correct A. \( pH = -\log[H^+] \)

B. \( pH = -\log[OH^-] \)

C. \( pH = \log \frac{[H^+]}{[OH^-]} \)

D. \( pH = \log \frac{[OH^-]}{[H^+]} \)

Correct Answer: A

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Question 6

Calculate the s\tandard enthalpy change \( ΔH^circ \) for the reaction: 2Al(s) + 6HCl(aq) → 2AlCl3(aq) + 3H2(g). Given that the s\tandard enthalpy of formation \( ΔH^circ_f \) for AlCl3 is -1669.0 kJ/mol, and for H2 is 0 kJ/mol. The s\tandard enthalpy of formation for Al is 0 kJ/mol. The s\tandard enthalpy of formation for HCl is -92.3 kJ/mol.

A. -1667.1 kJ/mol

Correct B. -1669.0 kJ/mol

C. -1671.0 kJ/mol

D. -1673.0 kJ/mol

Correct Answer: B

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Question 7

A sample of water (H2O) is contaminated with 0.5% \( w/w \) of a non-volatile solute. Calculate the mole \fraction of the solute in the solution.

A. 0.005

Correct B. 0.01

C. 0.015

D. 0.02

Correct Answer: B

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Question 8

A 2.5 L sample of a gas at 27°C and 1 atm is collected over water at 27°C. Calculate the partial pressure of the gas.

Correct A. 0.95 atm

B. 0.98 atm

C. 1.02 atm

D. 1.05 atm

Correct Answer: A

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Question 9

The s\tandard reduction potential (E°) for the half-reaction Zn2+ + 2e- → Zn(s) is -0.76 V. Calculate the s\tandard cell potential (E°cell) for the reaction: Zn(s) + Cu2+(aq) → Zn2+(aq) + Cu(s). Given that the s\tandard reduction potential (E°) for the half-reaction Cu2+ + 2e- → Cu(s) is +0.34 V.

Correct A. -1.10 V

B. -1.10 V

C. -1.10 V

D. -1.10 V

Correct Answer: A

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Question 10

A 25.0 mL sample of a 0.100 M solution of NaOH is mixed with a 25.0 mL sample of a 0.100 M solution of HCl. Calculate the pH of the resulting solution.

A. 1.00

Correct B. 2.00

C. 3.00

D. 4.00

Correct Answer: B

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Question 11

Determine the pH of a 0.1 M solution of HCl at 25°C.

A. 1

B. 2

C. 3

Correct D. 4

Correct Answer: D

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Question 12

A 25 mL sample of 0.5 M H2SO4 is titrated with 1 M NaOH. Calculate the number of moles of NaOH required to reach the equivalence point.

A. 0.025

B. 0.05

C. 0.075

Correct D. 0.1

Correct Answer: D

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Question 13

The rate cons\tant (k) for a first-order reaction is 0.05 min^-1. Calculate the half-life \( t1/2 \) of the reaction.

A. 1.4

Correct B. 2.8

C. 4.2

D. 5.6

Correct Answer: B

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Question 14

A 10 mL sample of 0.2 M NaOH is mixed with 20 mL of 0.1 M HCl. Calculate the pH of the resulting solution.

A. 1

B. 2

Correct C. 3

D. 4

Correct Answer: C

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Question 15

The solubility product cons\tant (Ksp) for AgCl is 1.8 x 10^-10. Calculate the molar solubility of AgCl.

A. 1.4 x 10^-5

B. 2.8 x 10^-5

Correct C. 4.2 x 10^-5

D. 5.6 x 10^-5

Correct Answer: C

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Question 16

The energy of an electron in the nth orbit of a hydrogen atom is given by the equation \( E_n = -\frac{13.6}{n^2} \) eV. What is the energy of an electron in the 3rd orbit of a hydrogen atom?

Correct A. -1.51 eV

B. -3.4 eV

C. -13.6 eV

D. -0.85 eV

Correct Answer: A

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Question 17

A sample of gas occupies a volume of 2.5 L at a pressure of 1.5 atm. If the temperature is increased to 300 K, what is the new volume of the gas?

Correct A. 3.75 L

B. 2.5 L

C. 1.25 L

D. 4.0 L

Correct Answer: A

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Question 18

The element with atomic number 12 is _______.

A. Mg

Correct B. Ca

C. Sr

D. Ba

Correct Answer: B

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Question 19

A polymer is a long chain of _______ molecules.

Correct A. monomers

B. polymers

C. atoms

D. molecules

Correct Answer: A

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Question 20

The process by which water is converted into hydrogen and oxygen is called _______.

A. photosynthesis

B. respiration

C. decomposition

Correct D. electrolysis

Correct Answer: D

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Question 21

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

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 22

A 2.5 g sample of a metal oxide is heated in a crucible until it is completely reduced to the pure metal. The mass of the metal obtained is 1.8 g. Calculate the percentage of the metal in the oxide.

A. 72%

Correct B. 80%

C. 90%

D. 92%

Correct Answer: B

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Question 23

The s\tandard enthalpy of formation of CO2(g) is -393.5 kJ/mol. Calculate the s\tandard enthalpy of formation of CO(g) if the s\tandard enthalpy of formation of O2(g) is 0 kJ/mol.

Correct A. -110.5 kJ/mol

B. -130.5 kJ/mol

C. -140.5 kJ/mol

D. -150.5 kJ/mol

Correct Answer: A

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Question 24

A 1.0 M solution of NaOH is mixed with a 1.0 M solution of HCl. If 50.0 mL of the NaOH solution is added to 50.0 mL of the HCl solution, 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 25

The half-life of a radioactive subs\tance is 5.0 years. If the initial activity of the subs\tance is 1000 Bq, what is the activity after 10 years?

A. 125 Bq

Correct B. 250 Bq

C. 500 Bq

D. 1000 Bq

Correct Answer: B

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