POST UTME REDEEMERS UNIVERSITY 2017 Chemistry | Objective

Practice these randomly selected questions to test your readiness.

Question 1
A 0.5 M solution of NaOH is titrated with 0.1 M HCl. Calculate the pH of the solution after 25 mL of HCl has been added.
A. ( 2.5 )
B. ( 3.5 )
C. ( 4.5 )
D. ( 5.5 )
Question 2
Determine the rate cons\tant (k) for the reaction: 2NO(g) + O2(g) → 2NO2(g) at 298 K, given that the initial concentrations of NO and O2 are 0.1 M and 0.05 M, respectively, and the rate of reaction is 3.2 × 10^\( -3 \) M/s.
A. \( 3.2 \times 10^{-3} \) M/s
B. \( 1.6 \times 10^{-3} \) M/s
C. \( 6.4 \times 10^{-3} \) M/s
D. \( 1.28 \times 10^{-3} \) M/s
Question 3
The reaction of cyclohexane with bromine in the presence of light yields a mixture of 1,2-dibromocyclohexane and 1,4-dibromocyclohexane. What is the major product of this reaction?
A. 1,2-dibromocyclohexane
B. 1,4-dibromocyclohexane
C. cis-1,2-dibromocyclohexane
D. trans-1,4-dibromocyclohexane
Question 4
A 2.50 L flask contains 0.500 mol of an ideal gas at 25°C. Calculate the pressure of the gas.
A. 1.01 x 10^5 Pa
B. 2.01 x 10^5 Pa
C. 3.01 x 10^5 Pa
D. 4.01 x 10^5 Pa
Question 5
A 2.5 M solution of HCl is prepared by dissolving 25 g of HCl in 1 L of water. What is the concentration of H+ ions in the solution?
A. 0.01 M
B. 0.1 M
C. 1 M
D. 10 M
Question 6
The half-life of a radioactive subs\tance is 5.00 years. If 100.0 g of the subs\tance initially decays to 50.0 g, how many years will it take for the subs\tance to decay to 12.5 g?
A. 10.00 years
B. 15.00 years
C. 20.00 years
D. 25.00 years
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 H2O(l) if the s\tandard enthalpy of formation of H2(g) is 0 kJ/mol and the s\tandard enthalpy of formation of O2(g) is 0 kJ/mol?
A. -285.8 kJ/mol
B. -241.8 kJ/mol
C. -393.5 kJ/mol
D. -483.5 kJ/mol
Question 8
A 2.5 g sample of a metal (X) is heated in a stream of oxygen to produce a green-colored solid. The mass of the solid produced is 3.2 g. Calculate the percentage yield of the reaction.
A. ( 80% )
B. ( 85% )
C. ( 90% )
D. ( 95% )
Question 9
A 1.00 M solution of HCl is titrated with 0.500 M NaOH. Calculate the pH of the solution after 25.0 mL of NaOH has been added.
A. 2.00
B. 3.00
C. 4.00
D. 5.00
Question 10
A metal (X) reacts with dilute HCl to produce a gas that gives a brown precipitate with KI solution. Identify the metal (X) and the gas produced.
A. Cu, SO2
B. Zn, SO2
C. Fe, SO2
D. Pb, SO2
Question 11
The atomic radius of an element in the periodic table increases down a group due to the addition of new energy levels. However, the atomic radius of an element in the periodic table decreases across a period due to the increase in effective nuclear charge. What is the correct explanation for this tr\end?
A. The addition of new energy levels increases the atomic radius.
B. The increase in effective nuclear charge decreases the atomic radius.
C. The atomic radius is inversely proportional to the atomic number.
D. The atomic radius is directly proportional to the atomic number.
Question 12
Determine the s\tandard enthalpy of formation of CaCO3(s) from the following data: ΔHf(CaO(s)) = -635.09 kJ/mol, ΔHf(CO2(g)) = -393.51 kJ/mol.
A. -1206.60 kJ/mol
B. -1206.61 kJ/mol
C. -1206.59 kJ/mol
D. -1206.62 kJ/mol
Question 13
A 2.5 M solution of HCl is prepared by dissolving 25 g of HCl in 1 L of water. What is the pH of the solution?
A. 1.3
B. 2.5
C. 3.5
D. 4.5
Question 14
A solution containing 0.1 M CuSO4 is mixed with a solution containing 0.1 M NaOH. Calculate the concentration of Cu(OH)2 formed after the reaction is complete.
A. ( 0.05 ) M
B. ( 0.1 ) M
C. ( 0.15 ) M
D. ( 0.2 ) M
Question 15
A 50 mL sample of a solution containing 0.1 M NaOH is titrated with 0.1 M HCl. What is the pH of the solution after the addition of 25 mL of HCl?
A. 1.3
B. 2.5
C. 3.5
D. 4.5

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