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POST UTME ELIZADE UNIVERSITY 2025 Chemistry | Objective

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Question 1 View Details

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 View Details

A sample of gas occupies a volume of 2.5 L at a temperature of 300 K and a pressure of 1 atm. What is the new volume of the gas when the temperature is increased to 400 K and the pressure is decreased to 0.5 atm?

Correct A. \( V_1 P_1 / T_1 = V_2 P_2 / T_2 \)

B. \( V_1 P_2 / T_2 = V_2 P_1 / T_1 \)

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

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

Correct Answer: A

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Question 3 View Details

A 2.5 M solution of NaOH is mixed with a 2.5 M solution of HCl. What is the resulting concentration of the solution?

A. \( C = 2.5 , \text{M} \)

B. \( C = 5.0 , \text{M} \)

C. \( C = 0.0 , \text{M} \)

Correct D. \( C = 1.25 , \text{M} \)

Correct Answer: D

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Question 4 View Details

A diagram of the apparatus for the reaction is shown below. Identify the part labeled A.

Correct A. The burette

B. The test tube

C. The thermometer

D. The stirrer

Correct Answer: A

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Question 5 View Details

A sample of a non-metallic element has a mass of 2.5 g and a volume of 1.0 L. What is the density of the element?

Correct A. \( \rho = \frac{m}{V} \)

B. \( \rho = \frac{V}{m} \)

C. \( \rho = mV \)

D. \( \rho = \frac{1}{mV} \)

Correct Answer: A

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Question 6 View Details

Determine the rate cons\tant for the reaction: 2NO(g) + O2(g) → 2NO2(g). The rate cons\tant is related to the rate equation by the equation: rate = k[NO]^2[O2]. If the rate of reaction is 0.05 M/s and the concentrations of NO and O2 are 0.02 M and 0.01 M, respectively, what is the rate cons\tant?

Correct A. 0.25 M^-1 s^-1

B. 0.5 M^-1 s^-1

C. 1.0 M^-1 s^-1

D. 2.0 M^-1 s^-1

Correct Answer: A

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Question 7 View Details

The reaction of nitrogen dioxide with water is represented by the equation: 3NO2(g) + H2O(l) → 2HNO3(aq) + NO(g). If 2.5 mol of NO2(g) reacts with 1.5 mol of H2O(l), what is the limiting reac\tant?

Correct A. NO2(g)

B. H2O(l)

C. HNO3(aq)

D. NO(g)

Correct Answer: A

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Question 8 View Details

The equilibrium cons\tant (Kc) for the reaction: N2(g) + O2(g) ⇌ 2NO(g) is 4.0 × 10^\( -4 \) at 298 K. If the initial concentrations of N2 and O2 are 0.10 M and 0.20 M, respectively, what is the equilibrium concentration of NO(g)?

Correct A. 0.02 M

B. 0.04 M

C. 0.06 M

D. 0.08 M

Correct Answer: A

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Question 9 View Details

The polymerization of ethylene to form polyethylene is represented by the equation: nC2H4 → [-CH2-CH2-]n. If 2.5 mol of C2H4 is polymerized, what is the number of moles of polyethylene produced?

A. 1.25 mol

Correct B. 2.5 mol

C. 3.75 mol

D. 5.0 mol

Correct Answer: B

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Question 10 View Details

The atomic radius of an atom is the dis\tance from the nucleus to the outermost electron. If the atomic radius of a certain atom is 1.5 × 10^\( -10 \) m, what is the volume of the atom?

Correct A. 2.25 × 10^\( -30 \) m^3

B. 4.5 × 10^\( -30 \) m^3

C. 6.75 × 10^\( -30 \) m^3

D. 9.0 × 10^\( -30 \) m^3

Correct Answer: A

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Question 11 View Details

The s\tandard enthalpy of formation of CO2(g) is -393.5 kJ/mol. Calculate the s\tandard enthalpy of formation of CaCO3(s) u\sing the following reaction: CaO(s) + CO2(g) → CaCO3(s).

Correct A. -1206.0 kJ/mol

B. -1206.5 kJ/mol

C. -1207.0 kJ/mol

D. -1207.5 kJ/mol

Correct Answer: A

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Question 12 View Details

A 2.50 M solution of HCl is mixed with a 1.00 M solution of NaOH. Calculate the pH of the resulting solution after the reaction is complete.

A. 1.00

Correct B. 2.00

C. 3.00

D. 4.00

Correct Answer: B

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Question 13 View Details

The diagram below shows a titration setup.

Correct A. The burette contains NaOH.

B. The beaker contains HCl.

C. The burette contains HCl.

D. The beaker contains NaOH.

Correct Answer: A

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Question 14 View Details

The s\tandard Gibbs free energy change for the reaction 2NO(g) + O2(g) → 2NO2(g) is 123.0 kJ/mol. Calculate the equilibrium cons\tant (K) for this reaction at 298 K.

Correct A. 1.00 x 10^5

B. 1.00 x 10^6

C. 1.00 x 10^7

D. 1.00 x 10^8

Correct Answer: A

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Question 15 View Details

A 0.100 M solution of NaOH is mixed with a 0.100 M solution of HCl. Calculate the pH of the resulting solution after the reaction is complete.

Correct A. 7.00

B. 8.00

C. 9.00

D. 10.00

Correct Answer: A

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Question 16 View Details

The diagram below shows a setup for a gas law experiment.

A. The cylinder contains a gas at cons\tant pressure.

Correct B. The thermometer measures the temperature of the gas.

C. The cylinder contains a gas at cons\tant volume.

D. The thermometer measures the pressure of the gas.

Correct Answer: B

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Question 17 View Details

A 1.00 M solution of HCl is mixed with a 1.00 M solution of NaOH. Calculate the pH of the resulting solution after the reaction is complete.

A. 1.00

Correct B. 2.00

C. 3.00

D. 4.00

Correct Answer: B

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Question 18 View Details

The s\tandard enthalpy of formation of H2O(l) is -285.8 kJ/mol. Calculate the s\tandard enthalpy of formation of NH3(g) u\sing the following reaction: N2(g) + 3H2(g) → 2NH3(g).

Correct A. -45.9 kJ/mol

B. -46.0 kJ/mol

C. -46.1 kJ/mol

D. -46.2 kJ/mol

Correct Answer: A

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Question 19 View Details

Determine the s\tandard enthalpy of formation of CaCO3(s) from the following data: ΔHf(CaO(s)) = -635.09 kJ/mol, ΔHf(CO2(g)) = -393.51 kJ/mol, and ΔHf(Ca(s)) = -178.2 kJ/mol.

Correct A. -1206.8 kJ/mol

B. -1206.9 kJ/mol

C. -1206.7 kJ/mol

D. -1206.6 kJ/mol

Correct Answer: A

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Question 20 View Details

A 2.5 L flask contains 0.15 mol of an ideal gas at 25°C. Calculate the pressure of the gas u\sing the ideal gas law.

Correct A. 1.01 atm

B. 1.02 atm

C. 1.03 atm

D. 1.04 atm

Correct Answer: A

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Question 21 View Details

The reaction between H2(g) and Cl2(g) produces HCl(g). If 1.5 mol of H2(g) reacts with 1.5 mol of Cl2(g), what is the limiting reac\tant?

Correct A. H2(g)

B. Cl2(g)

C. HCl(g)

D. Neither H2(g) nor Cl2(g) is the limiting reac\tant.

Correct Answer: A

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Question 22 View Details

A solution of 0.1 M HCl is titrated with 0.1 M NaOH. What is the pH of the solution after 25 mL of NaOH has been added?

A. 1

Correct B. 2

C. 3

D. 4

Correct Answer: B

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Question 23 View Details

A 100 mL sample of a solution containing 0.5 M HCl is titrated with 0.5 M NaOH. What is the volume of NaOH required to reach the equivalence point?

A. 50 mL

B. 75 mL

Correct C. 100 mL

D. 125 mL

Correct Answer: C

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Question 24 View Details

Determine the major product of the reaction between 2-methyl-2-propanol and acetic anhydride.

Correct A. 2-methyl-2-propyl acetate

B. 2-methyl-2-propanol

C. 2-methyl-2-propanone

D. 2-methyl-2-propanoic acid

Correct Answer: A

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Question 25 View Details

Calculate the number of moles of chlorine gas required to react with 2.5 moles of sodium bromide in the following reaction: 2NaBr + Cl2 → 2NaCl + Br2.

Correct A. 1.25

B. 2.5

C. 5

D. 10

Correct Answer: A

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