POST UTME REDEEMERS UNIVERSITY 2020 Chemistry | Objective
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Question 1
A polymer has a molecular weight of 50,000 g/mol and a degree of polymerization of 500. Calculate the molar mass of the repeating unit.
Question 2
A 2.0 M solution of HCl is titrated with a 2.0 M solution of NaOH. If 15 mL of the NaOH solution is required to reach the equivalence point, calculate the number of moles of HCl present in 50 mL of the HCl solution.
Question 3
A sample of oxygen gas is collected over water at a temperature of 25°C and a pressure of 1 atm. If the partial pressure of water vapor is 0.031 atm, what is the partial pressure of oxygen gas?
Question 4
A 2.5 g sample of a metal oxide is heated in a crucible until it loses 0.75 g of oxygen. If the metal has an atomic mass of 55.85 g/mol, calculate the mass of the metal in the sample.
Question 5
The s\tandard enthalpy change \( ΔH^circ \) for the reaction: C(s) + O2(g) → CO2(g) is -393.5 kJ/mol. Calculate the s\tandard entropy change \( ΔS^circ \) for the reaction, given that the s\tandard entropy of C(s) is 5.7 J/mol*K, the s\tandard entropy of O2(g) is 205.1 J/mol*K, and the s\tandard entropy of CO2(g) is 213.8 J/mol*K.
Question 6
A solution of 0.1 M NaCl is mixed with a solution of 0.1 M NaOH. What is the pH of the resulting solution?
Question 7
A sample of a non-metal has a mass of 2.5 g. If the density of the non-metal is 5.6 g/cm^3, what is the volume of the sample?
Question 8
A 0.1 M solution of HCl is titrated with 0.2 M NaOH. Calculate the pH of the solution after 20 mL of NaOH has been added.
Question 9
At 298 K, the s\tandard enthalpy change \( ΔH^circ \) for the reaction: CaCO3(s) → CaO(s) + CO2(g) is -178.2 kJ/mol. Calculate the s\tandard entropy change \( ΔS^circ \) for the reaction, given that the s\tandard entropy of CaCO3(s) is 92.9 J/mol*K, the s\tandard entropy of CaO(s) is 38.8 J/mol*K, and the s\tandard entropy of CO2(g) is 213.8 J/mol*K.
Question 10
A diagram of a titration setup is shown below. If 25 mL of 0.1 M NaOH is required to neutralize 20 mL of HCl, what is the concentration of the HCl solution?
Question 11
A sample of 2.5 g of a polymer is dissolved in 50 mL of a solvent. If the density of the polymer is 1.2 g/mL, calculate the volume of the polymer in the solution.
Question 12
The s\tandard Gibbs free energy change \( ΔG^circ \) for the reaction: 2AgCl(s) → 2Ag(s) + Cl2(g) is 67.3 kJ/mol. Calculate the equilibrium cons\tant (K) for the reaction.
Question 13
A 2.5 M solution of HCl is titrated with 0.5 M NaOH. Calculate the pH of the solution after 25 mL of NaOH has been added.
Question 14
Determine the number of moles of CO2 produced from the reaction of 2.5 g of calcium carbonate (CaCO3) with excess hydrochloric acid (HCl). The molar mass of CaCO3 is 100.09 g/mol, and the molar mass of CO2 is 44.01 g/mol.
Question 15
A sample of a polymer has a molecular weight of 200,000 g/mol. If the polymer has a degree of polymerization (n) of 500, what is the molecular weight of the repeating unit?
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