Final Exam Review Problem Set PDF

Preview

Summary

This is a problem set that covers all the topics that are covered in the course. It is representative of the amount of work that will be covered in the final exam, but it is significantly shorter than the actual final....

Description

CHEM 2090 Final Exam Review Sheet

1. A gas contains a mixture of NH3(g) and N2H4(g), both of which react with O2(g) to form NO2(g) and H2O(g). The gaseous mixture (with an initial mass of 61.00 g) is reacted with 10.00 moles O2, and after the reaction is complete, 4.062 moles O2 remains. Calculate the mass percent of N2H4(g) in the original gaseous mixture.

2. At 600 K and 1 bar, A2B3 is 1.2% dissociated according to the following equilibrium: A2B3(g) ⇌ 2A(g) + 3B(g) When the temperature is increased by 200°K, the compound is now 2.3% dissociated. Find the ΔH°rxn. Is this an endothermic or exothermic dissociation? If a plot of the lnK vs 1/T was made for this reaction, what would be the intercept?

3. The titration of 100.0 mL of 0.100 M HC2H3O2 (Ka = 1.8 x 10-5) with 0.100 M NaOH is carried out in a chemistry laboratory. Calculate the pH of the solution at each of the follow. Plot the titration curve. a. Before the addition of any NaOH b. After the addition of 50.0 mL of NaOH c. After the addition of 65.0 mL of NaOH d. After the addition of 100.0 mL NaOH e. After the addition of 120.0 mL NaOH

4. Balance the following: Br2 → Br- + BrO3 - (basic solution)

5. Chlorine gas was first prepared in 1774 by C.W. Scheele by oxidizing sodium chloride with manganese (IV) oxide. The reaction is: NaCl(aq) + H2SO4(aq) + MnO2(s)  Na2SO4(aq) + MnCl2(aq) + H2O(l) + Cl2(g) Balance this equation.

6. A 3.000 g sample of an unknown hydrocarbon undergoes complete combustion in a steel cylinder with a constant volume of 20.0 L initially filled with 1.0 atm of oxygen gas at 25°C. 8.80 g of CO2(g) and 5.40 g H2O(g) were produced in the reaction. a. Determine the empirical formula of the hydrocarbon. b. What is the pressure in the vessel after the container returns to its initial temperature? c. What is the partial pressure due to the remaining oxygen in the container?

7. A certain acetic acid solution has a pH = 2.68. a. Calculate the volume of 0.0975 M KOH required to reach the equivalence point in the titration of 25.0 mL of solution. b. How many mL of KOH have been added when a buffer with a pH = 5.00 has been prepared?

8. For the reaction 2A  2B + C, the following data were collected. [A] (M) 8.23 x 10-3 6.74 x 10-3 5.52 x 10-3 4.52 x 10-3 3.70 x 10-3 3.03 x 10-3 a. Determine the rate law

Time (min) 10 20 30 40 50 60

b. c. d. e.

Calculate k for this reaction Calculate the half-life for this reaction Calculate [A]0 Calculate [A] after 70 minutes

9. You have the following reagents on hand: Solids (pKa of Acid Form is Given) Benzoic Acid (4.19) Sodium acetate (4.74) Potassium fluoride (3.14) Ammonium chloride (9.26)

Solutions 5.0 M HCl 1.0 M acetic acid (4.74) 2.6 M NaOH 1.0 M HOCl (7.46)

What combination of reagents would you use to prepare buffers at the following pH values? a. 3.0

b. 4.0

c. 5.0

d. 7.0

e. 9.0

10. Calculate the longest and shortest wavelengths of light emitted by electrons in the hydrogen level that begin in the n = 6 state and then fall to the states with small values of n? Would these wavelengths be longer or shorter if this was Li2+ instead?

11. A sample of S8(g) is placed in an otherwise empty rigid container at 1325 K at an initial pressure of 1.00 atm, where it decomposes to S2(g) by the reaction S8(g) ⇄ 4S2(g) a. At equilibrium, the partial pressure of S8 is 0.25 atm. Calculate K for this reaction. b. If 0.5 atm of S8(g) and 1.8 atm of S2(g) are present, will the reaction shift towards the products, shift toward the reactant, or is the system at equilibrium?

12. Fill in the following table: Name of Orbital

Total nodes

Angular nodes

Radial Nodes

Number of Degenerate Orbitals

3d 5p 4f 6s 13. The standard enthalpy of formation of H2O(l) at 298 K is -285.8 kJ/mol. a. Calculate the change in the internal energy for the following process at 298 K and 1 atm: H2O(l)  H2(g) + 1/2O2(g) b. Determine the change in temperature of the system associated with 200. grams of H2O(l) undergoing the above process. Assume the reaction is taking place in a calorimeter with a heat capacity of 63.0 kJ/°C....