POST UTME LASU 2022 Chemistry | Objective

Practice these randomly selected questions to test your readiness.

Question 1
A 0.1 M solution of a weak acid HA is titrated with 0.1 M NaOH. If the initial pH of the acid solution is 3.5, what is the pH of the solution after the addition of 20 mL of 0.1 M NaOH?
A. 4.5
B. 5.5
C. 6.5
D. 7.5
Question 2
A metal M reacts with chlorine gas to form a white solid MX. If the molar mass of M is 55 g/mol and the molar mass of MX is 120 g/mol, what is the molar mass of X?
A. 65 g/mol
B. 75 g/mol
C. 85 g/mol
D. 95 g/mol
Question 3
Solve the equation \( \log_{10} \( x^2 \ \) = 4 ) for x.
A. 2
B. 4
C. 10
D. 20
Question 4
A sample of nitrogen gas (N2) occupies a volume of 2.5 liters at a pressure of 1 atm and a temperature of 298 K. Calculate the number of moles of N2 gas present in the sample.
A. 0.1 moles
B. 0.2 moles
C. 0.5 moles
D. 1 mole
Question 5
A sample of a polymer has a molecular weight of 50,000 g/mol. If the polymer has a degree of polymerization of 500, what is the molar mass of the monomer?
A. 100 g/mol
B. 200 g/mol
C. 300 g/mol
D. 400 g/mol
Question 6
A 0.1 M solution of NaOH is mixed with a 0.1 M solution of HCl. Calculate the pH of the resulting solution.
A. 1
B. 2
C. 3
D. 4
Question 7
A 0.500 M solution of HCl(aq) is mixed with 0.500 M solution of NaOH(aq). If the reaction is carried out in a calorimeter, and the temperature of the solution increases by 2.50°C, what is the value of ΔH for the reaction?
A. -54.0 kJ/mol
B. -45.0 kJ/mol
C. -36.0 kJ/mol
D. -27.0 kJ/mol
Question 8
The atomic radius of a certain element is 100 pm. If the element has an atomic number of 12, what is its electron configuration?
A. 1s² 2s² 2p⁶ 3s²
B. 1s² 2s² 2p⁶ 3s² 3p⁶
C. 1s² 2s² 2p⁶ 3s² 3p⁶ 4s²
D. 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 4p⁶
Question 9
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 nitrogen gas in the sample.
A. 0.95 atm
B. 0.99 atm
C. 1.00 atm
D. 1.05 atm
Question 10
The reaction of sodium hydroxide with hydrochloric acid is a classic example of a double displacement reaction. What is the net ionic equation for this reaction?
A. 2NaOH(aq) + 2HCl(aq) → 2NaCl(aq) + 2H2O(l)
B. NaOH(aq) + HCl(aq) → NaCl(aq) + H2O(l)
C. 2NaOH(aq) + 2HCl(aq) → 2NaCl(aq) + 2H2O(l)
D. NaOH(aq) + HCl(aq) → NaCl(aq) + H2O(l)
Question 11
A 0.1 M solution of sodium hydroxide is mixed with a 0.1 M solution of hydrochloric acid. What is the pH of the resulting solution?
A. 7
B. 8
C. 9
D. 10
Question 12
The diagram below shows a setup for electrolysis. What is the purpose of the salt bridge?
A. To prevent the mixing of the two solutions
B. To allow the flow of electrons
C. To maintain the electrical neutrality of the solutions
D. To increase the conductivity of the solutions
Question 13
A solution contains 2.5 grams of sodium chloride (NaCl) dissolved in 100 mL of water. Calculate the molarity of the solution.
A. 0.1 M
B. 0.2 M
C. 0.5 M
D. 1 M
Question 14
A 1.0 M solution of a non-electrolyte solute is prepared by dissolving 18 g of the solute in 1.0 L of water. What is the molar mass of the solute?
A. 18 g/mol
B. 20 g/mol
C. 22 g/mol
D. 24 g/mol
Question 15
A 0.1 M solution of H2SO4 is mixed with a 0.1 M solution of NaOH. Calculate the pH of the resulting solution.
A. 1
B. 2
C. 3
D. 4

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