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POST UTME NOUN 2020 Chemistry | Objective

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Question 1

In a batch reactor, a first-order reaction is carried out with an initial concentration of 0.1 M and a rate cons\tant of 0.05 min^-1. If the reaction is allowed to proceed for 10 minutes, what is the concentration of the reac\tant after 10 minutes?

Correct A. 0.05 M

B. 0.1 M

C. 0.2 M

D. 0.5 M

Correct Answer: A

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Question 2

A solution containing 0.1 M NaCl is electrolyzed u\sing a platinum electrode. If the electrolysis is carried out for 10 minutes, what is the volume of hydrogen gas produced at STP?

A. 0.5 L

Correct B. 1 L

C. 2 L

D. 5 L

Correct Answer: B

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Question 3

A 0.1 M solution of HCl is mixed with a 0.1 M solution of NaOH. If the reaction is allowed to proceed to completion, what is the pH of the resulting solution?

A. 1

B. 2

Correct C. 7

D. 14

Correct Answer: C

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Question 4

A 0.1 M solution of CH3COOH is mixed with a 0.1 M solution of NaOH. If the reaction is allowed to proceed to completion, what is the pH of the resulting solution?

A. 1

B. 2

Correct C. 7

D. 14

Correct Answer: C

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Question 5

A 0.1 M solution of CH3COOH is electrolyzed u\sing a platinum electrode. If the electrolysis is carried out for 10 minutes, what is the volume of hydrogen gas produced at STP?

A. 0.5 L

Correct B. 1 L

C. 2 L

D. 5 L

Correct Answer: B

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Question 6

Determine the oxidation state of the underlined atom in the compound [Cr_2O_7^{2-}].

Correct A. +6

B. +3

C. +2

D. +1

Correct Answer: A

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Question 7

A 25.0 mL sample of 0.100 M HCl is titrated with 0.100 M NaOH. Calculate the pH of the solution after the addition of 15.0 mL of NaOH.

A. 2.00

Correct B. 2.50

C. 3.00

D. 3.50

Correct Answer: B

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Question 8

The s\tandard enthalpy of formation of CO2(g) is -393.5 kJ/mol. Calculate the s\tandard enthalpy of formation of C2H6(g) if the s\tandard enthalpy of formation of H2(g) is -285.8 kJ/mol.

A. -83.8

B. -85.8

Correct C. -87.8

D. -89.8

Correct Answer: C

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Question 9

A 2.50 g sample of a compound containing only C, H, and O is analyzed by combustion. The volume of CO2 produced is 2.50 L at 25°C and 1.00 atm. The volume of H2O produced is 1.00 L at 25°C and 1.00 atm. Calculate the empirical formula of the compound.

Correct A. C2H4O

B. C3H6O

C. C4H8O

D. C5H10O

Correct Answer: A

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Question 10

A 10.0 mL sample of 0.100 M NaOH is titrated with 0.100 M HCl. Calculate the pH of the solution after the addition of 5.00 mL of HCl.

A. 2.00

Correct B. 2.50

C. 3.00

D. 3.50

Correct Answer: B

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Question 11

Determine the number of moles of glu\cose (C6H12O6) present in 250 mL of a 0.5 M solution.

A. 0.125 mol

Correct B. 0.25 mol

C. 0.5 mol

D. 1.0 mol

Correct Answer: B

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Question 12

A 2.5 L flask contains 0.5 mol of an ideal gas at 27°C. Calculate the pressure of the gas in atm.

A. 1.0 atm

Correct B. 2.0 atm

C. 3.0 atm

D. 4.0 atm

Correct Answer: B

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Question 13

A solution contains 5.0 g of NaCl in 250 mL of water. What is the molarity of the solution?

A. 0.2 M

Correct B. 0.5 M

C. 1.0 M

D. 2.0 M

Correct Answer: B

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Question 14

A 2.0 L flask contains 0.5 mol of an ideal gas at 27°C. Calculate the pressure of the gas in atm.

A. 1.0 atm

Correct B. 2.0 atm

C. 3.0 atm

D. 4.0 atm

Correct Answer: B

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Question 15

A solution contains 10.0 g of glu\cose (C6H12O6) in 250 mL of water. What is the molarity of the solution?

A. 0.2 M

B. 0.5 M

Correct C. 1.0 M

D. 2.0 M

Correct Answer: C

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Question 16

The reaction of sulfur with oxygen to form sulfur dioxide is represented by the equation: 2S(s) + 3O2(g) → 2SO2(g). Calculate the volume of oxygen gas required at STP to react with 2.5 g of sulfur.

A. 10.0 L

B. 15.0 L

Correct C. 20.0 L

D. 25.0 L

Correct Answer: C

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Question 17

The s\tandard enthalpy of formation of CO2(g) is -393.5 kJ/mol. Calculate the s\tandard enthalpy change for the reaction: CO(g) + 1/2O2(g) → CO2(g).

Correct A. -196.75 kJ/mol

B. -393.5 kJ/mol

C. -590.25 kJ/mol

D. -786.75 kJ/mol

Correct Answer: A

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Question 18

The reaction of sodium with water is represented by the equation: 2Na(s) + 2H2O(l) → 2NaOH(aq) + H2(g). Calculate the number of moles of hydrogen gas produced when 2.5 g of sodium reacts with excess water.

A. 0.25 mol

Correct B. 0.50 mol

C. 0.75 mol

D. 1.00 mol

Correct Answer: B

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Question 19

The s\tandard enthalpy of formation of NH3(g) is -45.9 kJ/mol. Calculate the s\tandard enthalpy change for the reaction: N2(g) + 3H2(g) → 2NH3(g).

A. -91.8 kJ/mol

Correct B. -182.7 kJ/mol

C. -273.6 kJ/mol

D. -364.5 kJ/mol

Correct Answer: B

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Question 20

The reaction of calcium with water is represented by the equation: Ca(s) + 2H2O(l) → Ca(OH)2(aq) + H2(g). Calculate the volume of hydrogen gas produced at STP when 2.5 g of calcium reacts with excess water.

A. 10.0 L

B. 15.0 L

Correct C. 20.0 L

D. 25.0 L

Correct Answer: C

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Question 21

The entropy change (ΔS) for a reaction is given by the equation ΔS = ΔH/T. If the enthalpy change (ΔH) for a reaction is -50 kJ/mol and the temperature (T) is 298 K, calculate the entropy change (ΔS) in J/mol·K.

A. -0.17 J/mol·K

Correct B. -0.18 J/mol·K

C. -0.19 J/mol·K

D. -0.20 J/mol·K

Correct Answer: B

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Question 22

A sample of a polymer has a molecular weight of 100,000 g/mol. If the polymer has a density of 1.2 g/cm³, calculate the molar mass of the polymer in g/mol.

A. 83,333 g/mol

Correct B. 83,333.33 g/mol

C. 83,333.34 g/mol

D. 83,333.35 g/mol

Correct Answer: B

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Question 23

A reaction is represented by the equation: 2A + B → 2C + D. If the rate cons\tant (k) for the reaction is 0.05 s⁻¹, calculate the rate of reaction (r) if the concentration of A is 0.1 M and the concentration of B is 0.2 M.

A. 0.002 M/s

Correct B. 0.0025 M/s

C. 0.003 M/s

D. 0.0035 M/s

Correct Answer: B

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Question 24

A solution of sodium hydroxide (NaOH) has a pH of 12. If the concentration of NaOH is 0.1 M, calculate the concentration of hydrogen ions (H⁺) in the solution.

A. 1.0 × 10⁻¹² M

B. 1.0 × 10⁻¹¹ M

Correct C. 1.0 × 10⁻¹⁰ M

D. 1.0 × 10⁻⁹ M

Correct Answer: C

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Question 25

A sample of a metal has a density of 8.0 g/cm³ and a volume of 10 cm³. If the metal is made of iron (Fe), calculate the mass of the metal in grams.

Correct A. 80 g

B. 80.1 g

C. 80.2 g

D. 80.3 g

Correct Answer: A

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