POST UTME ACHIEVERS UNIVERSITY 2023 Chemistry | Objective

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Question 1
The solubility of a sparingly soluble salt, AgCl, in water is 1.2 × 10^\( -5 \) mol/L at 25°C. Calculate the molar solubility of AgCl in a saturated solution at 50°C, given that the temperature dep\endence of the solubility of AgCl is described by the equation: \log(s) = - 1230/T + 2.5, where s is the solubility in mol/L and T is the temperature in Kelvin.
A. 1.8 × 10^\( -5 \)
B. 2.1 × 10^\( -5 \)
Correct C. 2.5 × 10^\( -5 \)
D. 3.0 × 10^\( -5 \)

Correct Answer: C

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Question 2
A 2.5 L flask contains 0.5 mol of an ideal gas at 25°C. Calculate the work done by the gas when it expands to 5 L against a cons\tant external pressure of 1.5 atm.
A. 1.9 kJ
Correct B. 2.1 kJ
C. 2.3 kJ
D. 2.5 kJ

Correct Answer: B

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Question 3
A 0.5 M solution of NaOH is prepared by dissolving 25 g of NaOH in 1 L of water. Calculate the number of moles of NaOH dissolved.
A. 0.05 mol
Correct B. 0.1 mol
C. 0.15 mol
D. 0.2 mol

Correct Answer: B

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Question 4
A 1.0 L flask contains 0.2 mol of CO2 at 25°C. Calculate the partial pressure of CO2 in the flask.
A. 0.5 atm
Correct B. 0.7 atm
C. 0.9 atm
D. 1.1 atm

Correct Answer: B

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Question 5
A 0.5 M solution of HCl is prepared by dissolving 25 g of HCl in 1 L of water. Calculate the pH of the solution.
A. 0.5
Correct B. 1.0
C. 1.5
D. 2.0

Correct Answer: B

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Question 6
A 0.1 M solution of a monoprotic acid is titrated with 0.1 M NaOH. If the initial pH of the acid solution is 2.5, what is the pH after 20 mL of NaOH has been added?
A. 2.5
Correct B. 3.5
C. 4.5
D. 5.5

Correct Answer: B

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Question 7
The s\tandard enthalpy of formation of CO2(g) is -393.5 kJ/mol. What is the s\tandard enthalpy of formation of CO(g)?
Correct A. -110.5 kJ/mol
B. -130.5 kJ/mol
C. -150.5 kJ/mol
D. -170.5 kJ/mol

Correct Answer: A

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Question 8
A sample of nitrogen gas occupies a volume of 2.5 L at a pressure of 1.5 atm and a temperature of 298 K. What is the new volume of the gas if the pressure is increased to 3.0 atm at cons\tant temperature?
A. 1.5 L
B. 2.5 L
Correct C. 3.5 L
D. 4.5 L

Correct Answer: C

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Question 9
The diagram below shows a titration setup. What is the purpose of the burette?
A. To measure the volume of the acid
Correct B. To measure the volume of the base
C. To mix the acid and base
D. To measure the pH of the solution

Correct Answer: B

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Question 10
The s\tandard enthalpy of formation of H2O(l) is -285.8 kJ/mol. What is the s\tandard enthalpy of formation of H2(g)?
Correct A. 0 kJ/mol
B. 10 kJ/mol
C. 20 kJ/mol
D. 30 kJ/mol

Correct Answer: A

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Question 11
The reaction of sodium hydroxide with hydrochloric acid is represented by the equation: NaOH + HCl → NaCl + H2O. If 25.0 mL of 0.100 M NaOH is added to 25.0 mL of 0.100 M HCl, what is the concentration of the resulting solution?
A. 0.0500 M
Correct B. 0.100 M
C. 0.200 M
D. 0.500 M

Correct Answer: B

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Question 12
A 2.50 L flask contains 0.500 mol of an ideal gas at a temperature of 298 K. If the gas is heated to 373 K, what is the new volume of the gas?
A. 3.00 L
B. 3.50 L
Correct C. 4.00 L
D. 4.50 L

Correct Answer: C

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Question 13
A solution contains 0.100 M NaOH and 0.100 M HCl. What is the pH of the solution?
A. 1.00
B. 2.00
C. 3.00
Correct D. 4.00

Correct Answer: D

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Question 14
A 2.00 L flask contains 0.500 mol of an ideal gas at a temperature of 298 K. If the gas is compressed to 1.00 L, what is the new pressure of the gas?
A. 2.00 atm
B. 3.00 atm
C. 4.00 atm
Correct D. 5.00 atm

Correct Answer: D

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Question 15
A solution contains 0.100 M NaOH and 0.100 M HCl. What is the concentration of the resulting solution?
A. 0.0500 M
Correct B. 0.100 M
C. 0.200 M
D. 0.500 M

Correct Answer: B

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Question 16
The reaction between chlorine gas and potassium iodide is represented by the equation: Cl2 + 2KI → 2KCl + I2. If 1.5 g of KI is reacted with an excess of Cl2, what is the limiting reac\tant?
Correct A. KI
B. Cl2
C. KCl
D. I2

Correct Answer: A

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Question 17
A 2.5 M solution of HCl is mixed with a 1.8 M solution of NaOH. What is the resulting pH?
A. 1
B. 2
Correct C. 3
D. 4

Correct Answer: C

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Question 18
The diagram below shows a titration setup. Identify the part labeled A.
Correct A. Burette
B. Beaker
C. Test tube
D. Cylinder

Correct Answer: A

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Question 19
A 0.5 M solution of H2SO4 is mixed with a 0.3 M solution of NaOH. What is the resulting pH?
A. 1
B. 2
Correct C. 3
D. 4

Correct Answer: C

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Question 20
The reaction between sodium hydroxide and acetic acid is represented by the equation: CH3COOH + NaOH → CH3COONa + H2O. If 1.2 g of CH3COOH is reacted with an excess of NaOH, what is the limiting reac\tant?
Correct A. CH3COOH
B. NaOH
C. CH3COONa
D. H2O

Correct Answer: A

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Question 21
A solution containing 0.1 M HCl is titrated with 0.1 M NaOH. If 20 mL of NaOH is added, what is the pH of the resulting solution?
A. 1
Correct B. 2
C. 3
D. 4

Correct Answer: B

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Question 22
A 0.5 M solution of K2Cr2O7 is electrolyzed u\sing a platinum electrode. What is the mass of Cr2O3 produced after 2 hours of electrolysis?
A. 10 g
B. 20 g
Correct C. 30 g
D. 40 g

Correct Answer: C

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Question 23
A 1 M solution of H2SO4 is titrated with 1 M NaOH. If 20 mL of NaOH is added, what is the pH of the resulting solution?
A. 1
Correct B. 2
C. 3
D. 4

Correct Answer: B

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Question 24
A 0.5 M solution of K2Cr2O7 is electrolyzed u\sing a platinum electrode. What is the mass of Cr2O3 produced after 2 hours of electrolysis?
A. 10 g
B. 20 g
Correct C. 30 g
D. 40 g

Correct Answer: C

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Question 25
A 1 M solution of H2SO4 is titrated with 1 M NaOH. If 20 mL of NaOH is added, what is the pH of the resulting solution?
A. 1
Correct B. 2
C. 3
D. 4

Correct Answer: B

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