POST UTME UNIBEN 2019 Chemistry | Objective

Practice these randomly selected questions to test your readiness.

Question 1
A solution of sodium hydroxide (NaOH) has a pH of 12.5. What is the concentration of the hydroxide ions in the solution?
A. 0.010 M
B. 0.020 M
C. 0.030 M
D. 0.040 M
Question 2
A solution of 0.1 M HCl is prepared by dissolving 3.0 g of HCl in 100 mL of water. What is the pH of the solution?
A. 1
B. 2
C. 3
D. 4
Question 3
The reaction between ethene (C2H4) and hydrogen (H2) in the presence of a catalyst is represented by the equation: C2H4 + H2 → C2H6. If 100 mL of a 2.0 M ethene solution is mixed with 50 mL of a 4.0 M hydrogen solution, what is the limiting reac\tant?
A. Ethene
B. Hydrogen
C. Neither ethene nor hydrogen is the limiting reac\tant
D. Both ethene and hydrogen are the limiting reac\tants
Question 4
A 0.500 M solution of NaOH is mixed with a 0.500 M solution of HCl. What is the pH of the resulting solution?
A. 7.00
B. 7.00
C. 7.00
D. 7.00
Question 5
A solution of 0.100 M HCl is titrated with 0.100 M NaOH. What is 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 6
A 1.0 M solution of H2SO4 is mixed with a 2.0 M solution of NaOH. Calculate the pH of the resulting solution after 10 minutes, given that the initial pH is 2.
A. ( 4 )
B. ( 5 )
C. ( 6 )
D. ( 7 )
Question 7
A 2.50-g sample of a metal oxide is heated in a crucible until it decomposes completely. The mass of the metal obtained is 1.25 g. What is the empirical formula of the oxide?
A. MgO
B. CaO
C. Fe2O3
D. CuO
Question 8
A sample of 1.0 g of a compound containing only carbon and oxygen is analyzed by combustion. The volume of CO2 produced is 1.5 L at 25°C and 1 atm. What is the empirical formula of the compound?
A. CO
B. C2O2
C. C3O3
D. C4O4
Question 9
Determine the molar mass of a compound containing 40.0% carbon, 6.7% hydrogen, and 53.3% oxygen by mass. The atomic masses of carbon, hydrogen, and oxygen are 12.01 g/mol, 1.008 g/mol, and 16.00 g/mol, respectively.
A. 120 g/mol
B. 140 g/mol
C. 160 g/mol
D. 180 g/mol
Question 10
The atomic radius of an element in Group 1 of the Periodic Table is 250 pm. If the element is in its +1 oxidation state, what is the radius of its ion?
A. 240 pm
B. 250 pm
C. 260 pm
D. 270 pm
Question 11
A diagram of a titration setup is shown below. If 25.0 mL of 0.100 M NaOH is required to reach the equivalence point, what is the concentration of the HCl solution?
A. 0.100 M
B. 0.100 M
C. 0.100 M
D. 0.100 M
Question 12
A diagram of a titration setup is shown below. If 50.0 mL of 0.100 M NaOH is required to reach the equivalence point, what is the concentration of the HCl solution?
A. 0.100 M
B. 0.100 M
C. 0.100 M
D. 0.100 M
Question 13
The rate cons\tant (k) of a first-order reaction is given by the equation: k = Ae^\( -Ea/RT \). If the activation energy (Ea) is 100 kJ/mol, the gas cons\tant (R) is 8.314 J/mol*K, and the temperature (T) is 300 K, calculate the value of k when A = 2.5 s^\( -1 \) and R = 8.314 J/mol*K.
A. 0.0002 s^\( -1 \)
B. 0.002 s^\( -1 \)
C. 0.02 s^\( -1 \)
D. 0.2 s^\( -1 \)
Question 14
The reaction between ammonia (NH3) and oxygen (O2) in the presence of a catalyst is represented by the equation: 4NH3 + 5O2 → 4NO + 6H2O. If 100 mL of a 2.0 M ammonia solution is mixed with 50 mL of a 4.0 M oxygen solution, what is the limiting reac\tant?
A. Ammonia
B. Oxygen
C. Neither ammonia nor oxygen is the limiting reac\tant
D. Both ammonia and oxygen are the limiting reac\tants
Question 15
A 1.00 M solution of NaOH is mixed with a 1.00 M solution of HCl. What is the pH of the resulting solution?
A. 7.00
B. 7.00
C. 7.00
D. 7.00

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