POST UTME PAN-ATLANTIC UNIVERSITY 2023 Chemistry | Objective

Practice these randomly selected questions to test your readiness.

Question 1
A sample of air contains 21.0% O2, 78.0% N2, and 1.0% Ar by volume. What is the partial pressure of Ar in a sample of air at 1.00 atm and 25.0°C?
A. 0.010 atm
B. 0.010 kPa
C. 0.010 bar
D. 0.010 MPa
Question 2
A 5.00 g sample of a compound containing only carbon and hydrogen is analyzed by combustion. If 3.25 g of CO2 and 1.75 g of H2O are collected, calculate the empirical formula of the compound.
A. C2H4
B. C3H6
C. C4H8
D. C5H10
Question 3
A 0.500 M solution of NaOH is prepared by dissolving 25.0 g of NaOH in 1.00 L of water. What is the pH of the solution?
A. 12.0
B. 13.0
C. 14.0
D. 15.0
Question 4
A 25.0 mL sample of 0.100 M NaOH is added to 25.0 mL of 0.100 M HCl. Calculate the pH of the resulting solution.
A. 1.00
B. 2.00
C. 3.00
D. 4.00
Question 5
A sample of air contains 21.0% O2, 78.0% N2, and 1.0% Ar by volume. What is the partial pressure of O2 in a sample of air at 1.00 atm and 25.0°C?
A. 0.210 atm
B. 0.210 kPa
C. 0.210 bar
D. 0.210 MPa
Question 6
A 2.00 M solution of HCl is prepared by dissolving 40.0 g of HCl in 1.00 L of water. What is the pH of the solution?
A. 0.0
B. 1.0
C. 2.0
D. 3.0
Question 7
A 2.00 L flask contains 0.150 M C6H12O6. Calculate the concentration of C6H12O6 after 50.0% of the glu\cose has decomposed.
A. 0.075 M
B. 0.100 M
C. 0.125 M
D. 0.150 M
Question 8
Determine the rate cons\tant (k) for the reaction: 2NO(g) + O2(g) → 2NO2(g), given that the initial concentrations of NO and O2 are 0.1 M and 0.2 M, respectively, and the rate of reaction is 0.05 M/s after 10 minutes.
A. \( k = \frac{2.303}{t} \log left\( \frac{[NO]_0 [O_2]_0}{[NO_2]_t} \right \ \) )
B. \( k = \frac{2.303}{t} \log left\( \frac{[NO_2]_t}{[NO]_0 [O_2]_0} \right \ \) )
C. \( k = \frac{2.303}{t} \log left\( \frac{[NO]_0 [O_2]_0}{[NO_2]_t} \right \ \) )
D. \( k = \frac{2.303}{t} \log left\( \frac{[NO_2]_t}{[NO]_0 [O_2]_0} \right \ \) )
Question 9
Determine the number of moles of ΔH2O formed when 2.5 g of glu\cose (C6H12O6) is completely oxidized in a reaction with oxygen gas. The balanced equation for the reaction is: C6H12O6 + 6O2 → 6CO2 + 6H2O.
A. 0.25 mol
B. 0.5 mol
C. 1.0 mol
D. 1.5 mol
Question 10
A 1.00 L sample of a gas at 25°C and 1.00 atm is collected over water at 25°C. If the vapor pressure of water at 25°C is 23.8 torr, what is the partial pressure of the gas?
A. 0.976 atm
B. 1.00 atm
C. 1.02 atm
D. 1.04 atm
Question 11
A polymer is formed by the condensation reaction between a diol and a diacid. The reaction is represented by the equation: \( HO-R-OH + HO-R'-COOH \rightarrow HO-R-O-CO-R'-OH + H_2O \). If 25.0 g of the diol and 30.0 g of the diacid are reacted, what is the limiting reac\tant?
A. The diol
B. The diacid
C. Neither the diol nor the diacid is the limiting reac\tant
D. The limiting reac\tant cannot be determined without more information
Question 12
A 0.500 M solution of NaOH is prepared by dissolving 25.0 g of NaOH in 1.00 L of water. What is the concentration of Na+ ions in the solution?
A. 0.500 M
B. 1.00 M
C. 2.00 M
D. 5.00 M
Question 13
Calculate the s\tandard enthalpy change (ΔH°) for the reaction: 2Al(s) + 3H2(g) → 2AlH3(s). Given that the s\tandard enthalpy of formation (ΔHf°) of AlH3 is -33.1 kJ/mol and the s\tandard enthalpy of formation (ΔHf°) of Al is 0 kJ/mol.
A. -66.2 kJ/mol
B. -33.1 kJ/mol
C. -22.1 kJ/mol
D. -11.0 kJ/mol
Question 14
A 0.5 M solution of HCl is mixed with a 0.5 M solution of NaOH. What is the pH of the resulting solution?
A. 1
B. 2
C. 3
D. 4
Question 15
A 1.0 M solution of HCl is prepared by dissolving 37 g of HCl in 1000 mL of water. What is the concentration of the solution in g/L?
A. 37 g/L
B. 37.5 g/L
C. 38 g/L
D. 40 g/L

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