Practice Post UTME UNIBEN chemistry 2022 Past Questions

Question 1 View Details

A polymer is formed by the condensation reaction between a diol and a diacid. The molecular weight of the polymer is 500 g/mol. If 2.5 g of the polymer is dissolved in 25 mL of water, what is the concentration of the polymer solution in g/L?

A. 50 g/L

Correct B. 100 g/L

C. 150 g/L

D. 200 g/L

Correct Answer: B

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Question 2 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

B. 2

Correct C. 3

D. 4

Correct Answer: C

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Question 3 View Details

A sample of 2.5 g of a subs\tance is found to have a mass of 2.2 g after being heated in a furnace at 1000°C for 1 hour. What is the percentage loss in mass?

A. 12%

Correct B. 15%

C. 18%

D. 20%

Correct Answer: B

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Question 4 View Details

A solution of 0.1 M HCl is titrated with 0.1 M NaOH. What is the number of moles of HCl that reacts with 25 mL of NaOH?

A. 0.0025 mol

Correct B. 0.005 mol

C. 0.0075 mol

D. 0.01 mol

Correct Answer: B

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Question 5 View Details

A diagram of a titration setup is shown below. What is the purpose of the burette?

Correct A. To measure the volume of the titrant

B. To measure the volume of the analyte

C. To mix the titrant and analyte

D. To measure the pH of the solution

Correct Answer: A

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Question 6 View Details

A 2.50-g sample of a metal carbonate is heated to produce a metal oxide and carbon dioxide gas. If the mass of the metal oxide produced is 1.75 g, calculate the percentage yield of the metal oxide.

A. 75%

B. 80%

Correct C. 85%

D. 90%

Correct Answer: C

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Question 7 View Details

A solution of sodium hydroxide (NaOH) is titrated with a solution of hydrochloric acid (HCl). If 25.0 mL of NaOH solution requires 32.5 mL of HCl solution to reach the \endpoint, calculate the concentration of the NaOH solution.

A. 0.100 M

B. 0.200 M

Correct C. 0.300 M

D. 0.400 M

Correct Answer: C

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Question 8 View Details

A 2.00-g sample of a metal carbonate is heated to produce a metal oxide and carbon dioxide gas. If the mass of the metal oxide produced is 1.75 g, calculate the percentage yield of the metal oxide.

A. 75%

B. 80%

Correct C. 85%

D. 90%

Correct Answer: C

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Question 9 View Details

A solution of sodium hydroxide (NaOH) is titrated with a solution of hydrochloric acid (HCl). If 25.0 mL of NaOH solution requires 32.5 mL of HCl solution to reach the \endpoint, calculate the concentration of the NaOH solution.

A. 0.100 M

B. 0.200 M

Correct C. 0.300 M

D. 0.400 M

Correct Answer: C

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Question 10 View Details

A 2.50-g sample of a metal carbonate is heated to produce a metal oxide and carbon dioxide gas. If the mass of the metal oxide produced is 1.75 g, calculate the percentage yield of the metal oxide.

A. 75%

B. 80%

Correct C. 85%

D. 90%

Correct Answer: C

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Question 11 View Details

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 $\text{CaC}_2(s) \rightarrow \text{Ca} (s) + \text{C} (s) + \text{CO}_2(g)$, given that the molar mass of $\text{CaC}_2$ is 64.10 g/mol.

A. 0.0391 mol

Correct B. 0.0394 mol

C. 0.0397 mol

D. 0.0400 mol

Correct Answer: B

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Question 12 View Details

A 2.5 L flask contains 0.50 mol of an ideal gas at 298 K. Calculate the pressure of the gas in pascals.

Correct A. 101325 Pa

B. 101350 Pa

C. 101375 Pa

D. 101400 Pa

Correct Answer: A

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Question 13 View Details

A solution contains 5.0 g of $\text{NaCl}$ in 250 mL of water. Calculate the molarity of the solution.

A. 0.20 M

Correct B. 0.25 M

C. 0.30 M

D. 0.35 M

Correct Answer: B

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Question 14 View Details

A 10.0 mL sample of a solution containing 0.50 M $\text{HCl}$ is titrated with 0.10 M $\text{NaOH}$. Calculate the number of moles of $\text{NaOH}$ required to reach the equivalence point.

Correct A. 0.0050 mol

B. 0.0055 mol

C. 0.0060 mol

D. 0.0065 mol

Correct Answer: A

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Question 15 View Details

A 2.0 L flask contains 0.50 mol of an ideal gas at 298 K. Calculate the number of molecules of the gas.

Correct A. 6.02 x 10^22

B. 6.04 x 10^22

C. 6.06 x 10^22

D. 6.08 x 10^22

Correct Answer: A

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Question 16 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 17 View Details

A 2.50 M solution of HCl is titrated with 0.500 M NaOH. What is the pH of the solution after 25.0 mL of NaOH has been added?

A. 2.00

B. 2.50

Correct C. 3.00

D. 3.50

Correct Answer: C

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Question 18 View Details

A colloidal solution of starch in water is 0.50 M. What is the concentration of the dispersed phase?

A. 0.25 M

Correct B. 0.50 M

C. 0.75 M

D. 1.00 M

Correct Answer: B

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Question 19 View Details

A 0.100 M solution of HCl is titrated with 0.500 M NaOH. What is the pH of the solution after 25.0 mL of NaOH has been added?

A. 1.00

Correct B. 2.00

C. 3.00

D. 4.00

Correct Answer: B

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Question 20 View Details

A 2.50 M solution of HCl is titrated with 0.500 M NaOH. What is the concentration of the excess HCl after 25.0 mL of NaOH has been added?

A. 0.50 M

Correct B. 1.00 M

C. 1.50 M

D. 2.00 M

Correct Answer: B

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Question 21 View Details

A colloidal solution of starch in water is 0.50 M. What is the concentration of the dispersed phase?

A. 0.25 M

Correct B. 0.50 M

C. 0.75 M

D. 1.00 M

Correct Answer: B

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Question 22 View Details

A 0.100 M solution of HCl is titrated with 0.500 M NaOH. What is the pH of the solution after 25.0 mL of NaOH has been added?

A. 1.00

Correct B. 2.00

C. 3.00

D. 4.00

Correct Answer: B

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Question 23 View Details

A 2.50 M solution of HCl is titrated with 0.500 M NaOH. What is the concentration of the excess HCl after 25.0 mL of NaOH has been added?

A. 0.50 M

Correct B. 1.00 M

C. 1.50 M

D. 2.00 M

Correct Answer: B

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Question 24 View Details

A colloidal solution of starch in water is 0.50 M. What is the concentration of the dispersed phase?

A. 0.25 M

Correct B. 0.50 M

C. 0.75 M

D. 1.00 M

Correct Answer: B

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Question 25 View Details

A 0.1 M solution of a weak acid HA is titrated with 0.1 M NaOH. If 20 mL of NaOH is required to reach the equivalence point, what is the initial concentration of HA?

A. 0.05 M

B. 0.1 M

Correct C. 0.2 M

D. 0.5 M

Correct Answer: C

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