POST UTME UNILORIN 2018 Chemistry | Objective

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Question 1
A sample of polystyrene is subjected to a temperature of 100°C for 30 minutes. Calculate the percentage of crystallinity of the sample.
A. ( 20% )
B. ( 30% )
C. ( 40% )
D. ( 50% )
Question 2
A 5.0 g sample of a subs\tance is found to have a mass of 2.5 g when dried. Calculate the percentage of water in the subs\tance.
A. 20%
B. 30%
C. 40%
D. 50%
Question 3
A solution containing 0.5 M H2SO4 is mixed with a solution containing 0.5 M NaOH. Calculate the pH of the resulting solution.
A. 1
B. 2
C. 7
D. 14
Question 4
A 25.0 mL sample of 0.100 M HCl is titrated with 0.100 M NaOH. Calculate the pH of the solution after the addition of 25.0 mL of NaOH.
A. 2.00
B. 2.50
C. 3.00
D. 3.50
Question 5
A solution of $HCl$ in water is prepared by dissolving $20,g$ of $HCl$ in $100,mL$ of water. Calculate the molar concentration of the solution.
A. 0.5 M
B. 1.0 M
C. 2.0 M
D. 5.0 M
Question 6
A solution of $NH_4Cl$ in water is prepared by dissolving $10,g$ of $NH_4Cl$ in $100,mL$ of water. Calculate the molar concentration of the solution.
A. 0.1 M
B. 0.2 M
C. 0.5 M
D. 1.0 M
Question 7
A 1.0 M solution of potassium permanganate is titrated with a 1.0 M solution of oxalic acid. Calculate the number of moles of oxalic acid required to react with 50 mL of the potassium permanganate solution.
A. ( 0.05 ) mol
B. ( 0.10 ) mol
C. ( 0.15 ) mol
D. ( 0.20 ) mol
Question 8
A 0.1 M solution of sodium hydroxide is mixed with a 0.1 M solution of acetic acid. Calculate the pH of the resulting solution.
A. ( 7.0 )
B. ( 7.5 )
C. ( 8.0 )
D. ( 8.5 )
Question 9
Determine the molar solubility of AgCl in a 0.1 M NaCl solution, given that the solubility product cons\tant (Ksp) for AgCl is 1.8 x 10^-10.
A. 1.0 x 10^-5 M
B. 1.5 x 10^-5 M
C. 2.0 x 10^-5 M
D. 3.0 x 10^-5 M
Question 10
A gas at $27^circ C$ and $1.0,atm$ is expanded to $0.5,atm$. Calculate the final volume of the gas, given that the initial volume is $10,L$.
A. 5.0 L
B. 10 L
C. 20 L
D. 40 L
Question 11
A 2.0 L sample of a gas at 25°C and 1 atm is collected over water. Calculate the partial pressure of the gas.
A. 0.5 atm
B. 1 atm
C. 1.5 atm
D. 2 atm
Question 12
A 0.1 M solution of sodium hydroxide is mixed with a 0.1 M solution of hydrochloric acid. Calculate the concentration of the resulting solution.
A. ( 0.1 ) M
B. ( 0.2 ) M
C. ( 0.3 ) M
D. ( 0.4 ) M
Question 13
Determine the number of moles of oxygen gas (O2) produced at STP when 2.5 moles of hydrogen gas (H2) react with oxygen gas according to the equation: 2H2 + O2 → 2H2O.
A. 1.25 moles
B. 2.5 moles
C. 5 moles
D. 10 moles
Question 14
A 50.0 g sample of a metal oxide is heated in a crucible until it is completely reduced to the metal. If the mass of the metal produced is 35.0 g, calculate the percentage yield of the reaction.
A. 70%
B. 75%
C. 80%
D. 85%
Question 15
The half-life of a radioactive subs\tance is $10,years$. If the initial amount of the subs\tance is $100,g$, how much of the subs\tance will remain after $20,years$?
A. 20 g
B. 40 g
C. 50 g
D. 60 g

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