Practice Post UTME EKSU chemistry 2017 Past Questions

Question 1

The s\tandard enthalpy of formation of CO2(g) is -393.5 kJ/mol. Calculate the s\tandard enthalpy of combustion of 1 mole of C6H12O6(s) at 298 K.

Correct A. -2814.5 kJ/mol

B. -2814.5 kJ/mol

C. -2814.5 kJ/mol

D. -2814.5 kJ/mol

Correct Answer: A

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Question 2

A 2.50 M solution of HCl is mixed with a 1.00 M solution of NaOH. 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 3

The atomic radius of an element is 100 pm. If the element has an electron configuration of [Ar] 4s^2 3d^5, what is the expected oxidation state of the element?

A. +2

Correct B. +3

C. +4

D. +5

Correct Answer: B

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Question 4

A sample of a non-metallic element has a mass of 25.0 g and a volume of 5.00 mL. If the density of the element is 3.00 g/mL, what is the expected boiling point of the element?

A. 100°C

B. 200°C

Correct C. 300°C

D. 400°C

Correct Answer: C

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Question 5

A 1.00 M solution of HCl is mixed with a 1.00 M solution of NaOH. Calculate the number of moles of HCl that react with NaOH.

Correct A. 1.00 mol

B. 2.00 mol

C. 3.00 mol

D. 4.00 mol

Correct Answer: A

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Question 6

The reaction of chlorine gas with sodium hydroxide solution is a classic example of a redox reaction. Write the balanced chemical equation for this reaction.

A. 2NaOH + Cl2 → NaCl + NaClO + H2O

Correct B. 2NaOH + Cl2 → NaClO + NaCl + H2O

C. 2NaOH + Cl2 → NaCl + NaClO3 + H2O

D. 2NaOH + Cl2 → NaClO + NaOH + H2O

Correct Answer: B

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Question 7

The diagram below shows a titration setup. Identify the part labeled A.

Correct A. The burette

B. The beaker

C. The pipette

D. The flask

Correct Answer: A

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Question 8

The atomic radius of an element increases down a group in the periodic table. Explain why this is the case.

Correct A. Due to the increase in the number of energy levels

B. Due to the decrease in the effective nuclear charge

C. Due to the increase in the atomic mass

D. Due to the decrease in the atomic number

Correct Answer: A

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Question 9

The diagram below shows a simple black and white chemistry apparatus showing a titration setup. Identify the part labeled A.

Correct A. The burette

B. The beaker

C. The pipette

D. The flask

Correct Answer: A

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Question 10

The reaction of sulfur dioxide with oxygen is a classic example of a redox reaction. Write the balanced chemical equation for this reaction.

Correct A. 2SO2 + O2 → 2SO3

B. 2SO2 + O2 → 2SO2O

C. 2SO2 + O2 → 2SO2O2

D. 2SO2 + O2 → 2SO2O3

Correct Answer: A

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Question 11

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 25.0 mL of NaOH.

A. 1.00

B. 2.00

Correct C. 3.00

D. 4.00

Correct Answer: C

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Question 12

The half-life of a radioactive subs\tance is 5.0 days. If 100 mg of the subs\tance is present initially, how much will remain after 15 days?

Correct A. 12.5 mg

B. 25.0 mg

C. 50.0 mg

D. 100 mg

Correct Answer: A

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Question 13

A 2.50 g sample of a non-metallic element is heated in a crucible until it reaches a temperature of 2500°C. If the element has a molar mass of 40.0 g/mol, what is the number of moles of the element present?

A. 0.0625 mol

B. 0.125 mol

Correct C. 0.250 mol

D. 0.500 mol

Correct Answer: C

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Question 14

A 1.00 L solution of 0.100 M NaOH is mixed with 1.00 L of 0.100 M HCl. What is the pH of the resulting solution?

A. 7.00

Correct B. 7.50

C. 8.00

D. 9.00

Correct Answer: B

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Question 15

A 2.50 g sample of a non-metallic element is heated in a crucible until it reaches a temperature of 2500°C. If the element has a molar mass of 40.0 g/mol, what is the number of moles of the element present?

A. 0.0625 mol

B. 0.125 mol

Correct C. 0.250 mol

D. 0.500 mol

Correct Answer: C

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Question 16

The solubility of a gas in a liquid is given by the equation: \( S = \frac{P}{k} \), where S is the solubility, P is the partial pressure of the gas, and k is a cons\tant. If the partial pressure of a gas is 2 atm and the cons\tant k is 0.5 atm, what is the solubility of the gas in the liquid?

A. 4 atm

B. 2 atm

Correct C. 1 atm

D. 0.5 atm

Correct Answer: C

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Question 17

A 2.5 M solution of NaCl is prepared by dissolving 25 g of NaCl in 1000 mL of water. What is the concentration of Na+ ions in the solution?

A. 0.1 M

Correct B. 0.2 M

C. 0.5 M

D. 1 M

Correct Answer: B

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Question 18

A 1.0 M solution of HCl is prepared by dissolving 36.5 g of HCl in 1000 mL of water. What is the concentration of H+ ions in the solution?

A. 0.1 M

B. 0.5 M

Correct C. 1 M

D. 2 M

Correct Answer: C

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Question 19

A 2.0 M solution of NaOH is prepared by dissolving 40 g of NaOH in 1000 mL of water. What is the concentration of OH- ions in the solution?

A. 0.1 M

B. 0.5 M

C. 1 M

Correct D. 2 M

Correct Answer: D

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Question 20

A 1.5 M solution of H2SO4 is prepared by dissolving 49 g of H2SO4 in 1000 mL of water. What is the concentration of H+ ions in the solution?

A. 0.1 M

B. 0.5 M

Correct C. 1 M

D. 2 M

Correct Answer: C

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Question 21

Determine the number of moles of glu\cose (C6H12O6) that can be obtained from 2.5 moles of ethanoic acid (CH3COOH) in a reaction where ethanoic acid reacts with glu\cose to form carbon dioxide, water, and ethanol.

A. 1.25 moles

B. 2.5 moles

Correct C. 3.75 moles

D. 5 moles

Correct Answer: C

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Question 22

A 2.5 M solution of sodium hydroxide (NaOH) is titrated with a 1.0 M solution of hydrochloric acid (HCl). If 25 cm^3 of the acid is required to reach the equivalence point, calculate the number of moles of NaOH present in 100 cm^3 of the solution.

A. 0.0125 moles

Correct B. 0.025 moles

C. 0.0375 moles

D. 0.05 moles

Correct Answer: B

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Question 23

A sample of air contains 20% oxygen, 70% nitrogen, and 10% carbon dioxide by volume. If the total volume of the air sample is 1000 cm^3, calculate the volume of oxygen present in the sample.

A. 100 cm^3

Correct B. 200 cm^3

C. 300 cm^3

D. 400 cm^3

Correct Answer: B

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Question 24

A 2.0 M solution of ammonia (NH3) is titrated with a 1.0 M solution of hydrochloric acid (HCl). If 20 cm^3 of the acid is required to reach the equivalence point, calculate the number of moles of NH3 present in 100 cm^3 of the solution.

A. 0.01 moles

Correct B. 0.02 moles

C. 0.03 moles

D. 0.04 moles

Correct Answer: B

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Question 25

A sample of a polymer contains 25% by mass of carbon, 60% by mass of hydrogen, and 15% by mass of oxygen. If the total mass of the sample is 100 g, calculate the mass of carbon present in the sample.

A. 10 g

Correct B. 20 g

C. 30 g

D. 40 g

Correct Answer: B

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