POST UTME BELLS UNIVERSITY 2019 Chemistry | Objective

Practice these randomly selected questions to test your readiness.

Question 1
A 2.5 L flask contains 0.5 mol of an ideal gas at 298 K. Calculate the pressure of the gas u\sing the ideal gas law.
A. 1.01 x 10^5 Pa
B. 2.02 x 10^5 Pa
C. 3.03 x 10^5 Pa
D. 4.04 x 10^5 Pa
Question 2
The reaction between nitrogen dioxide and water is an example of a redox reaction. Write the balanced chemical equation for this reaction, including the oxidation states of the nitrogen atom in the reac\tants and products.
A. \text{NO}_2 + \text{H}_2\text{O} \rightarrow \text{HNO}_3 + \text{H}_2\text{O}
B. \text{NO}_2 + \text{H}_2\text{O} \rightarrow \text{HNO}_3 + \text{NO}
C. \text{NO}_2 + \text{H}_2\text{O} \rightarrow \text{HNO}_3 + \text{H}_2\text{O}_2
D. \text{NO}_2 + \text{H}_2\text{O} \rightarrow \text{HNO}_3 + \text{NO}_2
Question 3
The reaction between calcium (Ca) and oxygen (O2) produces calcium oxide (CaO). Write the balanced chemical equation for this reaction.
A. 2Ca + O2 → 2CaO
B. Ca + O2 → CaO
C. 2Ca + O2 → CaO
D. Ca + O2 → 2CaO
Question 4
The half-life of a radioactive subs\tance is 5 years. If 100 g of the subs\tance decays to 50 g in 10 years, what is the decay cons\tant?
A. 0.05 yr^\( -1 \)
B. 0.10 yr^\( -1 \)
C. 0.15 yr^\( -1 \)
D. 0.20 yr^\( -1 \)
Question 5
A 2.5 M solution of NaOH is mixed with a 1.5 M solution of HCl. What is the resulting concentration of the solution?
A. 1.0 M
B. 2.0 M
C. 3.0 M
D. 4.0 M
Question 6
The reaction of an alkane with chlorine gas produces a dichloroalkane. If the alkane has the molecular formula C4H10, what is the structure of the dichloroalkane?
A. CH3CH2CH2CH2Cl2
B. CH3CH2CHClCH3
C. CH3CH2ClCH2CH3
D. CH3ClCH2CH2CH3
Question 7
The s\tandard enthalpy of formation of CO2 is -393.5 kJ/mol. What is the s\tandard enthalpy of formation of CO?
A. -110.5 \text{ kJ/mol}
B. -110.5 \text{ kJ/mol}
C. -110.5 \text{ kJ/mol}
D. -110.5 \text{ kJ/mol}
Question 8
A sample of gas occupies a volume of 2.5 liters at a pressure of 1.5 atm. What is the volume of the gas at a pressure of 3.0 atm, assuming the temperature remains cons\tant?
A. 1.0 L
B. 2.0 L
C. 3.0 L
D. 4.0 L
Question 9
The atomic radius of an element is 100 pm. If the element is in the 4th period, what is the expected value of its atomic radius in the 5th period?
A. 120 pm
B. 150 pm
C. 180 pm
D. 200 pm
Question 10
The atomic radius of an atom is the dis\tance from the nucleus to the outermost electron. Which of the following statements about atomic radius is correct?
A. Atomic radius decreases as the atomic number increases.
B. Atomic radius increases as the atomic number increases.
C. Atomic radius is the same for all elements.
D. Atomic radius is the dis\tance from the nucleus to the innermost electron.
Question 11
A 1.0 M solution of HCl is mixed with a 1.0 M solution of NaOH. What is the pH of the resulting solution?
A. 1
B. 2
C. 3
D. 4
Question 12
A metal oxide has the formula M2O3. If the metal has an atomic number of 24, what is the charge on the metal ion?
A. +3
B. +2
C. +1
D. +4
Question 13
A solution of a weak acid (HA) has a pH of 3. If the concentration of the acid is 0.1 M, what is the concentration of the hydrogen ions?
A. 0.01 M
B. 0.1 M
C. 1 M
D. 10 M
Question 14
A polymer has a molecular weight of 100,000 g/mol and a degree of polymerization of 500. What is the molar mass of the repeating unit?
A. 200 g/mol
B. 400 g/mol
C. 500 g/mol
D. 1000 g/mol
Question 15
A 2.0 M solution of NaOH is prepared by dissolving 40 g of NaOH in 1.0 L of water. What is the pH of the solution?
A. 12
B. 13
C. 14
D. 15

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