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POST UTME LEAD CITY UNIVERSITY 2021 Chemistry | Objective

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Question 1

Determine the molar mass of a polymer with the repeating unit (C6H5O2)n. Given that the molar mass of the repeating unit is 138.12 g/mol, calculate the molar mass of the polymer.

A. 138.12 g/mol

B. 276.24 g/mol

Correct C. 414.36 g/mol

D. 552.48 g/mol

Correct Answer: C

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Question 2

A solution of 0.1 M NaCl is prepared by dissolving 6.0 g of NaCl in 100 mL of water. What is the concentration of Cl- ions in the solution?

A. 0.05 M

Correct B. 0.1 M

C. 0.15 M

D. 0.2 M

Correct Answer: B

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Question 3

A sample of 1.0 g of a polymer is dissolved in 100 mL of solvent. The solution is then titrated with 0.1 M NaOH. If 25 mL of NaOH is required to reach the equivalence point, what is the molar mass of the polymer?

A. 100 g/mol

B. 200 g/mol

Correct C. 300 g/mol

D. 400 g/mol

Correct Answer: C

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Question 4

A mixture of 2.0 g of NaCl and 1.0 g of KCl is dissolved in 100 mL of water. What is the concentration of Cl- ions in the solution?

A. 0.05 M

Correct B. 0.1 M

C. 0.15 M

D. 0.2 M

Correct Answer: B

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Question 5

A solution of 0.1 M NaOH is prepared by dissolving 1.0 g of NaOH in 100 mL of water. What is the concentration of OH- ions in the solution?

A. 0.05 M

Correct B. 0.1 M

C. 0.15 M

D. 0.2 M

Correct Answer: B

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Question 6

A 2.5 g sample of a compound containing only carbon and hydrogen is found to have a mass of 1.25 g when burned in oxygen to produce carbon dioxide and water. Calculate the empirical formula of the compound.

A. CH2

B. CH3

C. C2H4

Correct D. C2H6

Correct Answer: D

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Question 7

A solution contains 5.0 g of NaCl in 250 mL of water. Calculate 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 8

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

A. 50 mL

Correct B. 75 mL

C. 100 mL

D. 125 mL

Correct Answer: B

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Question 9

A gas occupies a volume of 2.5 L at a pressure of 1.5 atm and a temperature of 25°C. Calculate the volume of the gas at a pressure of 3.0 atm and a temperature of 50°C.

A. 3.0 L

B. 4.0 L

Correct C. 5.0 L

D. 6.0 L

Correct Answer: C

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Question 10

A 1.0 g sample of a subs\tance is found to have a mass of 0.5 g when heated to 100°C. Calculate the percentage of water in the subs\tance.

A. 20%

B. 30%

Correct C. 40%

D. 50%

Correct Answer: C

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Question 11

The reaction between sulfuric acid (H2SO4) and sodium hydroxide (NaOH) is a classic example of a double displacement reaction. What is the balanced chemical equation for this reaction?

Correct A. H2SO4 + NaOH → Na2SO4 + H2O

B. H2SO4 + NaOH → NaHSO4 + H2O

C. H2SO4 + NaOH → Na2SO4 + H2O + NaOH

D. H2SO4 + NaOH → NaHSO4 + H2O + NaOH

Correct Answer: A

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Question 12

A 2.5 L sample of a gas at 27°C and 1 atm is collected over water. If the vapor pressure of water at 27°C is 26.7 mmHg, what is the partial pressure of the gas?

A. 1.2 atm

Correct B. 1.5 atm

C. 1.8 atm

D. 2.0 atm

Correct Answer: B

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Question 13

A 25 mL sample of a 0.1 M solution of sodium hydroxide (NaOH) is titrated with a 0.1 M solution of hydrochloric acid (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 14

A 5.0 g sample of a hydrocarbon is burned in a bomb calorimeter. If the heat of combustion is 35.5 kJ/g, what is the total heat of combustion for the sample?

A. 177.5 kJ

Correct B. 187.5 kJ

C. 197.5 kJ

D. 207.5 kJ

Correct Answer: B

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Question 15

A 10.0 mL sample of a 0.5 M solution of acetic acid (CH3COOH) is titrated with a 0.5 M solution of sodium hydroxide (NaOH). What is the pH of the resulting solution after the reaction is complete?

A. 4

B. 5

C. 6

Correct D. 7

Correct Answer: D

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Question 16

Calculate the s\tandard enthalpy change (ΔH°) for the reaction: 2Al(s) + 6HCl(aq) → 2AlCl3(aq) + 3H2(g). The s\tandard enthalpy of formation (ΔHf°) values are: Al(s) = 0 kJ/mol, HCl(aq) = -92.3 kJ/mol, AlCl3(aq) = -704.0 kJ/mol, H2(g) = 0 kJ/mol. Use the following equation: ΔH° = ΔHf°(products) - ΔHf°\( reac\tants \).

Correct A. -1452.6 kJ/mol

B. -704.0 kJ/mol

C. -92.3 kJ/mol

D. 1452.6 kJ/mol

Correct Answer: A

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Question 17

A 0.500 M solution of NaCl is prepared by dissolving 10.0 g of NaCl in 1.00 L of water. Calculate the molar solubility of NaCl.

A. 0.100 M

Correct B. 0.500 M

C. 1.00 M

D. 2.00 M

Correct Answer: B

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Question 18

The reaction between H2(g) and Cl2(g) is represented by the equation: H2(g) + Cl2(g) → 2HCl(g). If 1.00 mol of H2(g) reacts with 1.00 mol of Cl2(g), what is the limiting reac\tant?

Correct A. H2(g)

B. Cl2(g)

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

D. Both H2(g) and Cl2(g) are the limiting reac\tants.

Correct Answer: A

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Question 19

A 2.00 M solution of NaOH is prepared by dissolving 40.0 g of NaOH in 1.00 L of water. Calculate the molar solubility of NaOH.

Correct A. 0.200 M

B. 0.500 M

C. 1.00 M

D. 2.00 M

Correct Answer: A

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Question 20

A 0.500 M solution of HCl is prepared by dissolving 10.0 g of HCl in 1.00 L of water. Calculate the molar solubility of HCl.

A. 0.100 M

Correct B. 0.500 M

C. 1.00 M

D. 2.00 M

Correct Answer: B

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Question 21

Determine the pH of a 0.1 M solution of HCl at 25°C. The dissociation cons\tant of HCl is 10^\( -7 \).

A. 1

B. 2

C. 3

Correct D. 4

Correct Answer: D

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Question 22

A sample of a polymer has a molecular weight of 50000 g/mol. If 2.5 g of the polymer is dissolved in 100 mL of water, what is the concentration of the solution in g/L?

Correct A. 0.05

B. 0.1

C. 0.2

D. 0.5

Correct Answer: A

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Question 23

What is the molar mass of a compound that contains 40% carbon, 30% hydrogen, and 30% oxygen by mass?

A. 60

B. 80

Correct C. 100

D. 120

Correct Answer: C

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Question 24

A solution of NaOH is prepared by dissolving 10 g of NaOH in 100 mL of water. What is the concentration of the solution in M?

A. 0.1

B. 0.5

Correct C. 1

D. 2

Correct Answer: C

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Question 25

A sample of a hydrocarbon has a molecular formula of C5H12. What is the type of hydrocarbon?

Correct A. Alkane

B. Alkene

C. Alkyne

D. Aromatic

Correct Answer: A

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