POST UTME GREENFIELD UNIVERSITY 2020 Chemistry | Objective

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Question 1
A polymer is formed by the condensation reaction between a diol and a diacid. If 2.5 g of diol and 3.2 g of diacid are used, and the molecular weight of the diol is 62 g/mol and that of the diacid is 74 g/mol, calculate the number of moles of the polymer formed.
A. 0.04 mol
B. 0.06 mol
C. 0.08 mol
D. 0.10 mol
Question 2
A 25.0 mL sample of 0.500 M NaOH is titrated with 0.100 M HCl. What is the pH of the solution after the addition of 25.0 mL of HCl?
A. 1.00
B. 2.00
C. 3.00
D. 4.00
Question 3
A solution of 0.1 M NaOH is mixed with a solution of 0.2 M HCl. Calculate the pH of the resulting solution.
A. 1
B. 2
C. 3
D. 4
Question 4
A 2.50 g sample of a subs\tance is dissolved in 25.0 mL of water. The resulting solution has a pH of 4.50. What is the molar concentration of the subs\tance?
A. 0.100 M
B. 0.200 M
C. 0.300 M
D. 0.400 M
Question 5
A 2.00 L sample of a gas at 25°C and 1.00 atm is compressed to 0.500 L at 50°C. Calculate the work done on the gas u\sing the equation ΔU = q + w.
A. -200 J
B. -400 J
C. -600 J
D. -800 J
Question 6
A sample of 1.5 g of an organic compound containing only carbon and hydrogen is analyzed by combustion. If 0.75 g of CO2 is produced, calculate the empirical formula of the compound.
A. CH2
B. CH3
C. C2H4
D. C2H6
Question 7
Determine the molar mass of a polymer with the following composition: 60% polyethylene (C2H4)n, 20% polypropylene (C3H6)n, and 20% polystyrene (C6H5CH)n. Assume the average molecular weight of the repeating units is 28 g/mol for polyethylene, 42 g/mol for polypropylene, and 104 g/mol for polystyrene.
A. 600 g/mol
B. 800 g/mol
C. 1000 g/mol
D. 1200 g/mol
Question 8
A 2.00 L sample of a gas at 25°C and 1.00 atm is compressed to 0.500 L at 50°C. Calculate the work done on the gas u\sing the equation ΔU = q + w.
A. -200 J
B. -400 J
C. -600 J
D. -800 J
Question 9
A solution of 0.5 M H2SO4 is mixed with a solution of 0.2 M NaOH. Calculate the pH of the resulting solution.
A. 1
B. 2
C. 3
D. 4
Question 10
Determine the pH of a 0.1 M solution of HCl.
A. 1
B. 2
C. 3
D. 4
Question 11
A 5.00 g sample of a metal is heated in a crucible until it reaches a temperature of 1000°C. The metal is then allowed to cool to 25°C. Calculate the change in entropy of the metal.
A. 10.0 J/K
B. 20.0 J/K
C. 30.0 J/K
D. 40.0 J/K
Question 12
A 50.0 mL sample of 0.500 M HCl is titrated with 0.100 M NaOH. What is the pH of the solution after the addition of 25.0 mL of NaOH?
A. 1.00
B. 2.00
C. 3.00
D. 4.00
Question 13
A solution of 0.100 M NaCl is prepared by dissolving 6.00 g of NaCl in 100 mL of water. Calculate the concentration of Cl- ions in the solution.
A. 0.050 M
B. 0.100 M
C. 0.150 M
D. 0.200 M
Question 14
A 25.0 mL sample of 0.500 M NaOH is titrated with 0.100 M HCl. What is the pH of the solution after the addition of 50.0 mL of HCl?
A. 1.00
B. 2.00
C. 3.00
D. 4.00
Question 15
The diagram below shows a titration setup. If 25 mL of 0.1 M NaOH is used to titrate 20 mL of 0.2 M HCl, calculate the number of moles of HCl present in the solution.
A. 0.02 mol
B. 0.04 mol
C. 0.06 mol
D. 0.08 mol

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