POST UTME WELLSPRING UNIVERSITY 2019 Chemistry | Objective

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Question 1
Calculate the s\tandard enthalpy change \( ΔH^circ \) for the reaction: 2Al(s) + 6HCl(aq) → 2AlCl_3(aq) + 3H_2(g). Given that ΔH^circ = -572.4 kJ/mol for AlCl_3(aq) and ΔH^circ = -92.3 kJ/mol for H_2(g).
A. -1072.1 kJ/mol
B. -572.4 kJ/mol
C. -92.3 kJ/mol
D. -1376.4 kJ/mol
Question 2
A 2.5 M solution of NaOH is prepared by dissolving 2.5 g of NaOH in 100 mL of water. What is the concentration of NaOH in the solution?
A. 0.0625 M
B. 0.125 M
C. 0.25 M
D. 0.5 M
Question 3
A 1.00 M solution of HCl is titrated with 1.00 M NaOH. What is the pH of the solution after 25.0 mL of NaOH has been added?
A. 1.00
B. 2.00
C. 3.00
D. 4.00
Question 4
A solution of 0.100 M NaOH is mixed with a solution of 0.100 M HCl. What is the pH of the resulting solution?
A. 1.00
B. 2.00
C. 3.00
D. 4.00
Question 5
A 1 M solution of NaOH is prepared by dissolving 40 g of NaOH in 1000 mL of water. What is the concentration of the solution in mol/L?
A. 0.1 M
B. 0.5 M
C. 1 M
D. 2 M
Question 6
A 2 M solution of a weak base B is titrated with 2 M HCl. If 20 mL of HCl is required to reach the equivalence point, calculate the number of moles of B present in 1 L of the solution.
A. 0.01 mol
B. 0.02 mol
C. 0.03 mol
D. 0.04 mol
Question 7
Determine the pH of a 0.1 M solution of HCl.
A. 1
B. 2
C. 3
D. 4
Question 8
A sample of 25.0 mL of 0.100 M HCl is titrated with 0.100 M NaOH. What is the pH of the solution after the reaction is complete?
A. 7.00
B. 8.00
C. 9.00
D. 10.00
Question 9
The s\tandard enthalpy change \( ΔH^circ \) for the reaction: 2Al(s) + 6HCl(aq) → 2AlCl_3(aq) + 3H_2(g) is -572.4 kJ/mol. Calculate the s\tandard entropy change \( ΔS^circ \) for the reaction.
A. -192.3 J/K
B. -192.4 J/K
C. -192.5 J/K
D. -192.6 J/K
Question 10
A 2.5 g sample of a polymer is dissolved in 50 mL of a solvent. The solution is then diluted to 100 mL. What is the concentration of the polymer solution in g/L?
A. 0.05 g/L
B. 0.1 g/L
C. 0.5 g/L
D. 1 g/L
Question 11
A 1.00 M solution of HCl is prepared by dissolving 36.5 g of HCl in 1.00 L of water. Calculate the pH of the solution.
A. 0.00
B. 1.00
C. 2.00
D. 3.00
Question 12
Calculate the s\tandard enthalpy change (ΔH°) for the reaction: 2Al(s) + Fe2O3(s) → 2Fe(s) + Al2O3(s). The s\tandard enthalpy of formation (ΔHf°) for Al2O3(s) is -1675.7 kJ/mol, and for Fe2O3(s) is -826.4 kJ/mol. The s\tandard enthalpy of formation for Al(s) is 0 kJ/mol, and for Fe(s) is 0 kJ/mol. Assume the reaction occurs at 298 K.
A. -1821.1 kJ/mol
B. -1821.5 kJ/mol
C. -1821.9 kJ/mol
D. -1822.3 kJ/mol
Question 13
The s\tandard enthalpy of formation of CO2 is -393.5 kJ/mol. The s\tandard enthalpy of formation of H2O is -285.8 kJ/mol. What is the s\tandard enthalpy of combustion of methane (CH4)?
A. -890.3 kJ/mol
B. -890.5 kJ/mol
C. -890.1 kJ/mol
D. -890.7 kJ/mol
Question 14
The half-life of a radioactive subs\tance is 3 years. If the initial activity is 500 Bq, what is the activity after 9 years?
A. 125 Bq
B. 250 Bq
C. 500 Bq
D. 1000 Bq
Question 15
A 0.500 M solution of NaOH is prepared by dissolving 25.0 g of NaOH in 1.00 L of water. Calculate the pH of the solution.
A. 12.3
B. 13.3
C. 14.3
D. 15.3

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