POST UTME NOUN 2022 Chemistry | Objective

Practice these randomly selected questions to test your readiness.

Question 1
The rate cons\tant (k) of a first-order reaction is related to the half-life \( t_\( 1/2 \ \)) by the equation: \( k = \frac{ln{2}}{t_{1/2}} \). If the half-life of a reaction is 20 minutes, what is the value of k?
A. 0.0347 min^\( -1 \)
B. 0.0357 min^\( -1 \)
C. 0.0367 min^\( -1 \)
D. 0.0377 min^\( -1 \)
Question 2
A gas occupies a volume of 2.5 L at a pressure of 1.5 atm. What is the volume of the gas if the pressure is increased to 3.0 atm?
A. 1.5 L
B. 2.0 L
C. 2.5 L
D. 3.0 L
Question 3
A 2.00-g sample of a metal is dissolved in 10.0 mL of acid. The resulting solution is then titrated with 0.100 M NaOH. If 25.0 mL of NaOH is required to reach the equivalence point, what is the molar mass of the metal?
A. 50.0 g/mol
B. 60.0 g/mol
C. 70.0 g/mol
D. 80.0 g/mol
Question 4
A solution of sodium hydroxide (NaOH) is titrated with a solution of hydrochloric acid (HCl). The initial pH of the NaOH solution is 12. If 25 mL of 0.1 M HCl is added to 25 mL of 0.1 M NaOH, what is the pH of the resulting solution?
A. 7
B. 8
C. 9
D. 10
Question 5
A 2.50-g sample of a compound containing only carbon and hydrogen is analyzed by combustion. The amount of CO_(2) produced is 1.25 g, and the amount of H_(2)O produced is 0.75 g. What is the empirical formula of the compound?
A. CH_(2)
B. C_(2)H_(4)
C. C_(3)H_(6)
D. C_(4)H_(8)
Question 6
A solution contains 0.1 M HCl and 0.2 M NaOH. What is the pH of the resulting solution?
A. 1
B. 2
C. 3
D. 4
Question 7
The reaction of sodium with water produces sodium hydroxide and hydrogen gas. Write the balanced chemical equation for this reaction, including the state of each subs\tance.
A. \text{Na}(s) + \text{H}_2\text{O}(l) \rightarrow \text{NaOH}(aq) + \text{H}_2(g)
B. \text{Na}(s) + 2\text{H}_2\text{O}(l) \rightarrow \text{NaOH}(aq) + \text{H}_2(g)
C. \text{Na}(s) + \text{H}_2\text{O}(l) \rightarrow \text{NaO}(aq) + \text{H}_2(g)
D. \text{Na}(s) + 2\text{H}_2\text{O}(l) \rightarrow \text{NaO}(aq) + \text{H}_2(g)
Question 8
The half-life of a radioactive subs\tance is 5 years. If 100 g of the subs\tance is present initially, how much will remain after 10 years?
A. 50 g
B. 75 g
C. 87.5 g
D. 100 g
Question 9
A gas occupies a volume of 2.5 L at a pressure of 1.5 atm. What is the pressure of the gas if the volume is reduced to 1.2 L?
A. 2.5 atm
B. 3.0 atm
C. 3.5 atm
D. 4.0 atm
Question 10
The solubility of a subs\tance in water is 0.5 g/100 mL. If 2.5 g of the subs\tance is added to 100 mL of water, what is the concentration of the solution in terms of molarity?
A. 0.1 M
B. 0.2 M
C. 0.5 M
D. 1.0 M
Question 11
A 1.00-L sample of a gas at 25°C and 1.00 atm is compressed to 2.00 atm at cons\tant temperature. What is the new volume of the gas?
A. 0.50 L
B. 0.75 L
C. 1.00 L
D. 1.25 L
Question 12
Determine the pH of a 0.1 M solution of HCl.
A. 1
B. 2
C. 3
D. 4
Question 13
The half-life of a radioactive subs\tance is 5 years. If a sample of this subs\tance has an initial activity of 100 Bq, what is its activity after 10 years?
A. 12.5 Bq
B. 25 Bq
C. 50 Bq
D. 100 Bq
Question 14
A 25 mL sample of 0.1 M HCl is titrated with 0.1 M NaOH. Calculate the pH of the solution after 20 mL of NaOH has been added.
A. ( 2.303 )
B. ( 4.605 )
C. ( 6.907 )
D. ( 9.209 )
Question 15
A solution contains 0.1 M NaOH and 0.1 M HCl. What is the pH of the solution after mixing?
A. 0
B. 1
C. 7
D. 14

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