Exam 1 2006
Multiple Choice
For all questions involving solutions and/or chemical equations, assume that the system is in water and at room temperature unless otherwise stated.
Each set of lettered choices below refers to the numbered questions or statements immediately following it. Select the one lettered choice that best answers each question or best fits each statement and then mark your choice on the answer sheet. A choice may be used once, more than once, or not at all in each set.
Questions 1-4
(A) oxygen gas
(B) hydrogen gas
(C) water
(D) air
1. Is a mixture?
2. These molecules would be moving fastest on average at room temperature.
3. Typically can exist as a liquid at 25 °C and 1 atm of pressure.
4. Has a molar mass of 32.0 g
Each of these questions or incomplete statements below is followed by five suggested answers or completions. Select the one that is best in each case and then mark your choice on the answer sheet.
5. The weight of H2SO4 in 50.0 ml of a 6.00 molar solution is
(A) 3.10 g
(B) 12.0 g
(C) 29.4 g
(D) 294 g
(E) 300 g
6. A gaseous mixture containing 7.0 moles of nitrogen, 2.5 moles of oxygen, and 0.50 mole of helium exerts a total pressure of 0.90 atm. What is the partial pressure of the nitrogen?
(A) 0.13 atm
(B) 0.27 atm
(C) 0.63 atm
(D) 0.90 atm
(E) 6.3 atm
7. 6 I- + 2 MnO4- + 4 H2O à 3 I2 + 2 MnO2 + 8 OH-
Which of the following statements regarding the reaction above is correct?
(A) Iodide ion is oxidized by the hydroxide ion.
(B) MnO4- is oxidized by the iodide ion.
(C) The oxidation number of manganese changes from +7 to +2.
(D) The oxidation number of manganese remains the same.
(E) The oxidation number of iodine changes from –1 to 0
8. How many grams of calcium nitrate contain 24 grams of oxygen atoms?
(A) 164 g
(B) 96 g
(C) 62 g
(D) 50 g
(E) 41 g
9. The mass of element Q found in 1.00 mole of each of four different compounds is 38.0 g, 57.0 g, 76.0 g, and 114 g, respectively. A possible atomic weight (molar mass) of Q is:
(A) 12.7
(B) 19.0
(C) 27.5
(D) 38.0
(E) 57.0
10. How many milliliters of 11.6 molar HCl must be diluted to obtain 1.0 liter of 3.0 molar HCl?
(A) 3.9 ml
(B) 35 ml
(C) 260 ml
(D) 1,000 ml
(E) 3,900 ml
11. 2 K + 2 HOH à 2 K+ + 2 OH- + H2
11. When 0.400 mole of potassium reacts with excess water at standard temperature and pressure as shown by the equation above, the volume of hydrogen gas produced is:
(A) 1.12 L
(B) 2.24 L
(C) 3.36 L
(D) 4.48 L
(E) 6.72 L
12. How many moles of solid Ba(NO3)2 should be added to 300.0 ml of 0.20 molar Fe(NO3)3 to increase the concentration of the NO3- ion to 1.0 molar. Assume that the volume remains constant.
(A) 0.060 mole
(B) 0.12 mole
(C) 0.24 mole
(D) 0.30 mole
(E) 0.40 mole
Free Response Questions:
Be sure to provide a complete answer for each question.
You must answer both questions 1 and 2 (5 points each)
1. A sample of an unknown gas is collected in a previously evacuated 1.0 L container. The gas is determined to have a mass of 0.82 g and exerts a pressure of 1.24 atm at a temperature of 23.0 °C. Determine the molar mass of this gas. BONUS: ID the gas.
2. A group of students is trying to determine the Molarity of a solution of NaOH. They weigh out 1.00 g of KHP (a monoprotic acid with a molar mass = 204 g), put the KHP into a flask and add 50.0 ml of water. They use the NaOH solution to titrate the KHP solution to the endpoint and use a volume of 45.9 ml of the NaOH solution. Use this data and determine the Molarity of the NaOH solution.
Select either 3 or 4 and clearly mark the question to be graded. (10 points)
3. Answer the following questions concerning hydrocarbons.
a. Determine the mass of carbon present in 45.0 g of methane, CH4.
b. The density of a gaseous hydrocarbon is 2.0 g L-1 at 50 °C and 0.948 atm.
(i) Determine the molar mass of this hydrocarbon.
(ii) Determine the number of moles of carbon dioxide that could be produced at these conditions if 2.00 g of this hydrocarbon is burned in air.
c. Two containers are connected by a valve as shown in the picture below. The 10.0 L flask contains CH4 at a pressure of 5.0 atm and the 5.0 L flask contains C2H6 at a pressure of 0.50 atm.
(i) Determine the total pressure in the system after the valve is opened. Assume that the pressure remains constant.
(ii) Which gas molecules in the system would be traveling at the highest velocity? Explain.
4. A mixture containing equal moles of H2, O2, CO2, and H2O is placed in a 2.0 L pressure vessel at 25 °C. The total pressure of in the vessel is 1555 torr. The vapor pressure of water at this temperature is 24 torr.
a. Determine the partial pressure of each gas in the mixture.
b. Determine the mass of water in the vessel.
c. The mixture is sparked and a reaction occurs.
(i) Write the balanced equation for the reaction that occurs in the vessel.
(ii) Determine the pressure in the vessel after the reaction occurs and the vessel cools back to a temperature of 25 °C.
You must do problem 5. (15 points)
5. 2.00 g of magnesium carbonate is dropped into a flask that contains 25.0 ml of 1.0 M hydrochloric acid.
(a) Write a balanced equation for the reaction that takes place in the flask.
(b) Determine the moles of magnesium carbonate that has been placed into the flask.
(c) Determine the moles of HCl that is present in the flask before the reaction.
(d) Determine the total number of moles of gas produced by this reaction.
(e) Exactly what species are going to be present in the flask upon completion of the reaction.
(f) Determine the number of moles of each species present in the flask upon completion of the reaction. The flask is NOT sealed.