POST UTME BELLS UNIVERSITY 2019 Chemistry | Objective

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Question 1
The reaction between sodium and chlorine is an example of a \single displacement reaction. Write the balanced chemical equation for this reaction, including the oxidation states of the sodium and chlorine atoms in the reac\tants and products.
A. \text{Na} + \text{Cl}_2 \rightarrow \text{NaCl}
B. \text{Na} + \text{Cl}_2 \rightarrow \text{Na}_2\text{Cl}_2
C. \text{Na} + \text{Cl}_2 \rightarrow \text{NaCl}_2
D. \text{Na} + \text{Cl}_2 \rightarrow \text{Na}_2\text{Cl}_3
Question 2
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 3
The reaction between sodium thiosulfate and iodine is a first-order reaction. If the initial concentration of sodium thiosulfate is 0.1 M and the rate cons\tant is 0.05 min^-1, calculate the concentration of sodium thiosulfate after 10 minutes.
A. 0.005 M
B. 0.01 M
C. 0.05 M
D. 0.1 M
Question 4
A 1.0 M solution of HCl is mixed with a 1.0 M solution of NaOH. What is the resulting concentration of the solution?
A. 0.5 M
B. 1.0 M
C. 1.5 M
D. 2.0 M
Question 5
A 2.5 M solution of H2SO4 is mixed with a 1.5 M solution of NaOH. 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
A sample of a polymer has a molecular weight of 100,000 g/mol. If 1.0 g of the polymer is dissolved in 100 mL of solvent, what is the concentration of the solution in g/L?
A. 0.1 g/L
B. 1.0 g/L
C. 10 g/L
D. 100 g/L
Question 7
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 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 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 10
The reaction between methane (CH4) and chlorine (Cl2) produces chloromethane (CH3Cl) and hydrogen chloride (HCl). Write the balanced chemical equation for this reaction.
A. CH4 + Cl2 → CH3Cl + HCl
B. CH4 + Cl2 → CH3Cl + HCl + Cl
C. CH4 + Cl2 → CH3Cl + HCl + Cl2
D. CH4 + Cl2 → CH3Cl + HCl + CH4
Question 11
A 10 g sample of a metal is heated in a Bunsen burner flame. The mass of the sample decreases by 2 g. What is the percentage increase in the mass of the sample?
A. 20%
B. 30%
C. 40%
D. 50%
Question 12
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 13
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 14
The solubility of a subs\tance in water is 0.5 g/100 mL at 25°C. If 10 g of the subs\tance is added to 100 mL of water at 25°C, what is the maximum amount of the subs\tance that can dissolve?
A. 2 g
B. 5 g
C. 10 g
D. 15 g
Question 15
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}

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