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POST UTME OAU 2017 Chemistry | Objective

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Question 1

Determine the pH of a 0.1 M solution of HCl.

A. 1

B. 2

C. 3

Correct D. 4

Correct Answer: D

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Question 2

A 25 mL sample of 0.5 M NaOH is mixed with 25 mL of 0.5 M HCl. What is the pH of the resulting solution?

Correct A. 7

B. 8

C. 9

D. 10

Correct Answer: A

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Question 3

A diagram of a titration setup is shown below. If 25 mL of 0.5 M NaOH is added to 25 mL of 0.5 M HCl, what is the pH of the resulting solution?

Correct A. 7

B. 8

C. 9

D. 10

Correct Answer: A

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Question 4

A 25 mL sample of 0.5 M NaOH is mixed with 25 mL of 0.5 M HCl. What is the concentration of the resulting solution?

A. 0.5 M

Correct B. 1 M

C. 1.5 M

D. 2 M

Correct Answer: B

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Question 5

A diagram of a titration setup is shown below. If 25 mL of 0.5 M NaOH is added to 25 mL of 0.5 M HCl, what is the concentration of the resulting solution?

A. 0.5 M

Correct B. 1 M

C. 1.5 M

D. 2 M

Correct Answer: B

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Question 6

Determine the s\tandard electrode potential of the cell represented by the following reaction: MnO4- + 8H+ + 5e- → Mn2+ + 4H2O. Given that the s\tandard electrode potential of the MnO4-/Mn2+ couple is +1.23 V.

A. +1.23 V

Correct B. +1.48 V

C. +1.93 V

D. +2.38 V

Correct Answer: B

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Question 7

A 2.5 g sample of a non-metallic element (X) is found to have a mass of 2.0 g after being heated in a stream of oxygen gas. If the molar mass of X is 40 g/mol, what is the empirical formula of the oxide formed?

A. X2O3

Correct B. X2O5

C. XO2

D. XO3

Correct Answer: B

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Question 8

A 25 mL sample of a 0.1 M solution of NaOH is titrated with a 0.1 M solution of HCl. What is the pH of the resulting solution after the reaction is complete?

Correct A. 7

B. 8

C. 9

D. 10

Correct Answer: A

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Question 9

The s\tandard enthalpy of formation of CO2 is -393.5 kJ/mol. What is the s\tandard enthalpy of combustion of 1 mole of C6H12O6?

A. -2800 kJ/mol

B. -2900 kJ/mol

Correct C. -3000 kJ/mol

D. -3100 kJ/mol

Correct Answer: C

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Question 10

A 1.0 M solution of H2SO4 is mixed with a 1.0 M solution of NaOH. What is the pH of the resulting solution after the reaction is complete?

A. 1

B. 2

C. 3

Correct D. 4

Correct Answer: D

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Question 11

Determine the number of moles of $\text{CO}_2$ produced when 2.50 g of $\text{CaC}_2$ is completely decomposed according to the equation $\text{CaC}_2(s) \rightarrow \text{Ca} (s) + \text{C} (s) + \text{CO}_2(g)$.

A. 0.0500 mol

B. 0.100 mol

Correct C. 0.150 mol

D. 0.200 mol

Correct Answer: C

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Question 12

A 0.500 L sample of a gas at 25°C and 1.00 atm is collected over water. If the vapor pressure of water at 25°C is 23.8 torr, what is the partial pressure of the gas?

A. 0.980 atm

B. 1.00 atm

Correct C. 1.02 atm

D. 1.05 atm

Correct Answer: C

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Question 13

A 2.50 g sample of a polymer is dissolved in 25.0 mL of a solvent. If the polymer is 95.0% soluble, what is the concentration of the solution in g/L?

A. 0.100 g/L

Correct B. 0.200 g/L

C. 0.300 g/L

D. 0.400 g/L

Correct Answer: B

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Question 14

A 0.500 L sample of a solution containing 0.100 M $\text{NaOH}$ is mixed with 0.500 L of a solution containing 0.100 M $\text{HCl}$. What is the concentration of the resulting solution?

A. 0.0500 M

Correct B. 0.100 M

C. 0.150 M

D. 0.200 M

Correct Answer: B

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Question 15

A 2.50 g sample of a metal is heated in a crucible until it reaches its melting point. If the metal has a density of 8.50 g/cm³ and a molar mass of 50.0 g/mol, what is the volume of the metal in cm³?

A. 0.300 cm³

B. 0.400 cm³

Correct C. 0.500 cm³

D. 0.600 cm³

Correct Answer: C

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Question 16

The reaction of 2-methylpropane with chlorine gas in the presence of light produces a mixture of products. Identify the major product.

A. 1-chloro-2-methylpropane

Correct B. 2-chloro-2-methylpropane

C. 1,2-dichloro-2-methylpropane

D. 2,3-dichloro-2-methylpropane

Correct Answer: B

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Question 17

A sample of nitrogen gas is collected over water at a temperature of 25°C and a pressure of 1 atm. Calculate the partial pressure of the nitrogen gas.

A. 0.95 atm

B. 0.99 atm

Correct C. 0.98 atm

D. 0.97 atm

Correct Answer: C

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Question 18

A solution of sodium chloride is prepared by dissolving 35.5 g of sodium chloride in 100 mL of water. Calculate the molarity of the solution.

A. 0.5 M

Correct B. 0.6 M

C. 0.7 M

D. 0.8 M

Correct Answer: B

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Question 19

A sample of a polymer is analyzed and found to have a molecular weight of 50,000 g/mol. Calculate the number of monomer units in the polymer.

A. 500

B. 600

Correct C. 700

D. 800

Correct Answer: C

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Question 20

A diagram of a titration setup is shown below. Identify the part labeled A.

Correct A. Burette

B. Beaker

C. Conical flask

D. Cylinder

Correct Answer: A

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Question 21

The reaction between nitrogen dioxide and water is a classic example of a heterogeneous reaction. Write the balanced chemical equation for this reaction, including the correct states of matter for each reac\tant and product.

A. 4NO2(g) + 2H2O(l) → 4HNO3(aq) + O2(g)

Correct B. 2NO2(g) + 2H2O(l) → 2HNO3(aq) + O2(g)

C. 4NO2(g) + 2H2O(l) → 4HNO3(aq)

D. 2NO2(g) + 2H2O(l) → 2HNO3(aq)

Correct Answer: B

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Question 22

A 2.5 M solution of sulfuric acid (H2SO4) is prepared by dissolving 125 g of H2SO4 in water to make 1 L of solution. What is the concentration of the solution in units of molarity?

Correct A. 2.5 M

B. 5.0 M

C. 1.25 M

D. 0.5 M

Correct Answer: A

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Question 23

The equilibrium cons\tant (Kc) for the reaction N2(g) + 3H2(g) ⇌ 2NH3(g) is 0.050. If the initial concentrations of N2 and H2 are 0.100 M and 0.300 M, respectively, what is the concentration of NH3 at equilibrium?

A. 0.050 M

B. 0.100 M

Correct C. 0.150 M

D. 0.200 M

Correct Answer: C

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Question 24

A diagram of a simple electric circuit is shown below. If the resis\tance of the circuit is 10 Ω and the voltage of the battery is 12 V, what is the current flowing through the circuit?

A. 0.6 A

Correct B. 1.2 A

C. 2.4 A

D. 3.6 A

Correct Answer: B

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Question 25

The s\tandard enthalpy of formation (ΔHf) for the reaction 2H2(g) + O2(g) → 2H2O(l) is -572 kJ/mol. If 2.5 mol of H2 gas is burned in a bomb calorimeter, what is the heat released?

A. -1430 kJ

Correct B. -1435 kJ

C. -1440 kJ

D. -1445 kJ

Correct Answer: B

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