POST UTME MOUNTAIN TOP UNIVERSITY 2017 Chemistry | Objective

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Question 1
The half-life of a radioactive subs\tance is 5 years. If the initial amount of the subs\tance is 100g, what is the amount remaining after 15 years?
A. 25g
B. 50g
C. 75g
D. 100g
Question 2
A 25.0 mL sample of a 0.100 M solution of NaOH is mixed with a 25.0 mL sample of a 0.100 M solution of HCl. Calculate the pH of the resulting solution.
A. 1.00
B. 2.00
C. 3.00
D. 4.00
Question 3
A 2.0 g sample of sulfur is burned in oxygen to produce sulfur dioxide gas. If the reaction is 100% efficient, what is the volume of SO2 produced at 298 K and 1 atm?
A. 2.4 L
B. 4.8 L
C. 6.2 L
D. 8.5 L
Question 4
A sample of nitrogen gas at 298 K and 1 atm is allowed to expand to twice its original volume. What is the new pressure of the gas, assuming ideal behavior?
A. 0.5 atm
B. 1 atm
C. 2 atm
D. 4 atm
Question 5
The element with atomic number 12 is _______.
A. Mg
B. Ca
C. Sr
D. Ba
Question 6
A polymer is a long chain of _______ molecules.
A. monomers
B. polymers
C. atoms
D. molecules
Question 7
A 0.1 M solution of NaOH is titrated with 0.1 M HCl. What is the pH of the solution after 50 mL of HCl has been added?
A. 1
B. 2
C. 3
D. 4
Question 8
The s\tandard enthalpy of formation of CO2(g) is -393.5 kJ/mol. Calculate the s\tandard enthalpy of formation of CO(g) if the s\tandard enthalpy of formation of O2(g) is 0 kJ/mol.
A. -110.5 kJ/mol
B. -130.5 kJ/mol
C. -140.5 kJ/mol
D. -150.5 kJ/mol
Question 9
A gas at 25°C and 1 atm is compressed to 4 atm. Calculate the new volume of the gas.
A. \( V_1 P_1 = V_2 P_2 \)
B. \( \frac{P_1 V_1}{T_1} = \frac{P_2 V_2}{T_2} \)
C. \( \frac{P_1 V_1}{T_1} = \frac{P_2 V_2}{T_2} \)
D. \( \frac{P_1 V_1}{T_1} = \frac{P_2 V_2}{T_2} \)
Question 10
The s\tandard enthalpy of formation of H2O(l) is -285.8 kJ/mol. Calculate the s\tandard enthalpy of formation of H2(g) if the s\tandard enthalpy of formation of O2(g) is 0 kJ/mol.
A. -228.6 kJ/mol
B. -248.6 kJ/mol
C. -258.6 kJ/mol
D. -268.6 kJ/mol
Question 11
A solution of 0.1 M HCl is titrated with 0.1 M NaOH. What is the pH of the solution after 50 mL of NaOH has been added?
A. 1
B. 2
C. 3
D. 4
Question 12
A solution contains 2.5g of NaCl in 100g of water. What is the molarity of the solution?
A. 0.1M
B. 0.2M
C. 0.3M
D. 0.4M
Question 13
A 0.1 M solution of NaOH is titrated with 0.1 M HCl. What is the pH of the solution after 50 mL of HCl has been added?
Question 14
The rate cons\tant (k) for a first-order reaction is 0.05 min^-1. Calculate the half-life \( t1/2 \) of the reaction.
A. 1.4
B. 2.8
C. 4.2
D. 5.6
Question 15
A 25.0 mL sample of 0.100 M HCl is titrated with 0.100 M NaOH. Calculate the pH of the solution after 25.0 mL of NaOH has been added.
A. \( pH = -\log[H^+] \)
B. \( pH = -\log[OH^-] \)
C. \( pH = \log \frac{[H^+]}{[OH^-]} \)
D. \( pH = \log \frac{[OH^-]}{[H^+]} \)

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