I. (40 points) A. (11 points) 1. Write the ions present in solution after Ba(OH) 2 reacts completely with nitric acid

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1 I. (40 points) A. (11 points) 1. Write the ions present in solution after Ba(OH) 2 reacts completely with nitric acid 2. Write balanced net ionic equations for the reactions between aqueous solutions of the following compounds. (Do not forget to write the states!) a. HF and NaOH b. Fe(NO 3 ) 3 and KOH c. NH 3 and HClO 4 B. (10 points) Ten ml of a M solution of NaOH is mixed with 10.0 ml of a M solution of Ca(OH) How many moles of OH are present in the final mixture? 2. Assuming that the final volume of the mixture is 20.0 ml, what is the molarity of Na + ions in the final mixture? 1

2 C. (9 points) Ten ml of a M solution of HBr is mixed with 10.0 ml of a M solution of Sr(OH) How many moles of OH are unreacted? 2. Assuming that the final volume of the mixture is 20.0 ml, what is the molarity of OH ions in the final mixture? D. (10 points) Twenty ml of a M solution of Co(Cl) 3 is mixed with 1.00 ml of a M solution of AgNO How many moles of chloride ions are initially present? 2. How many moles of silver ions are initially present? 3. How many grams of precipitate are formed? 2

3 II. (30 points) A. (16 points) Consider the reaction in acidic medium between liquid bromine and lead(iv) oxide. The unbalanced equation for this redox reaction is Br 2 (l) + PbO 2 (s) BrO 3 (aq) + Pb2+ (aq) Write a balanced net ionic equation for this reaction using smallest whole number coefficients. The equation itself will not be graded but you will need to balance it to answer the following questions. Write your answers on the blanks provided. 1. For the reaction, what species contains the element that has the highest oxidation number? 2. What is the element oxidized? 3. What species is the reducing agent? 4. How many electrons are lost in the balanced oxidation half-reaction? 5. In the balanced reduction half reaction (using smallest whole number coefficients) what is the coefficient for H +? Refer to your balanced redox reaction for the answers to the next 3 questions. 6. What is the coefficient for PbO 2? 7. Is H 2 O a reactant? 8. What is the sum of all the coefficients on the product side of the reaction? 3

4 B. (4 points) Write your answers on the blanks provided. Show work no matter how trivial. How many grams of KMnO 4 (MM = g/mol) are used to prepare 225 ml of a M solution of KMnO 4? C. (10 points) Hydrogen gas is bubbled into a solution of barium hydroxide that has sulfur in it. The balanced equation for the reaction that takes place is: H 2 (g) + S (s) + 2 OH (aq) S 2 (aq) + 2 H 2 O The following 2 questions are not related to each other. They only share a common reaction. 1. How many grams of hydrogen gas are required to completely react with g of sulfur? 2. What volume of M Ba(OH) 2 is required to react completey with 4.81 g of sulfur? 4

5 III. (55 points) A. (10 points) Write on the blanks provided whether each of the following statements is true (Y) or false (N). 1. After the pressure of one mole of gas is tripled (at constant temperature), its volume is three times greater than its original value. 2. The molar masses of He and O 2 are 4.0 g/ mol and 32 g / mol, respectively. At the same temperature and pressure, one mole of He(g) will occupy the same volume as one mole of O 2 (g). 3. Standard temperature and pressure (STP) conditions are defined as P = 1 atm and T = 0K 4. At a given temperature, molecules of O 2,SO 2, and F 2 have the same average velocity. 5. According to the kinetic theory, the gas pressure is caused by collisions of molecules with the container walls. B. (6 points) The weather report lists the barometric pressure as inches of Hg, when the temperature is 32 F. Express this pressure in both atmospheres and pascal. atm C. (6 points) An aerosol spray can with a volume of 325 ml contains 3.00 g of propane (C 3 H 8 ) as propellant. What is the pressure (in atm) of the gas in the can at 28 C? Pa 5

6 D. (6 points) A fixed quantity of gas at a constant temperature has a pressure of 737 mm Hg and occupies a volume of 20.5 L. What is the pressure (in atm) of the gas if the volume is decreased to 16.0 L? E. (6 points) The density of a noble (inert) gas is 2.71 g / L at 3.00 atm and 0 C. 1. What is molar mass of the gas? 2. Write the symbol of the gas. F. (5 points) At an underwater depth of 250 ft, the total pressure of diving gas must be 8.38 atm to equalize the external pressure occurring at this depth. What should the mole fraction of oxygen (O 2 ) in the diving gas be so that the partial pressure of oxygen in the diving gas mixture is 0.21 atm, the same as in air? 6

7 G. (6 points) When KClO 3 is heated, it decomposes producing O 2 (g). The gas, collected over water at 26 C, has a volume of of L and a total pressure of 765 mm Hg. How many moles of O 2 (g) are collected? (At 26 C, the vapor pressure of water is 25 mm Hg.) I. (10 points) A metal hydride, MH 2 reacts with water according to the equation: MH 2 (s)+2h 2 O(l) M(OH) 2 (s)+2h 2 (g) When g of MH 2 (s) reacts with water, 225 ml of dry H 2 (g) are produced at 16 C and atm. 1. How many moles of MH 2 (s) have reacted? 2. What is the molar mass of MH 2 (s)? 3. What is the symbol for the metal M? 7

8 IV. (25 points) A. (10 points) A certain halide salt of barium ( barium cation and halogen anion) has a mass of g. It is determined by experiment that the mass of the barium in the salt is g. 1. How many moles of Ba are present in the salt? 2. What is the mole ratio of barium to the halogen in the salt? Ba:X = : 3. How many moles of halide are there? 4. What is the molar mass of the halide? 5. The formula for the barium halide is 8

9 B. (15 points) A chloride salt weighs mg. It is dissolved in water and titrated with AgNO 3 using K 2 CrO 4 the indicator. To reach the end point ml of M AgNO 3 are used. 1. Write a balanced net ionic equation for the reaction that takes place during titration. 2. How many moles of silver are used to reach the end point? 3. How many grams of chloride are present in the salt? 4. What is the mass percent of chloride in the salt? 5. What is the color of the solution being titrated before and after the end point? before the endpoint after the endpoint 9

10 BONUS (15 points) All or nothing. The bonus should be done only after you have completed the main part of this exam and checked your work for errors. The time alloted for this exam does not include time for the bonus. Nitrogen reacts with hydrogen gas to give ammonia. Consider two bulbs connected by a valve. Bulb A has a volume of 1.00 L and contains nitrogen gas at a pressure of 0.50 atm. Bulb B has a volume of 0.90 L and contains hydrogen gas at a pressure of 1.1 atm. What is the pressure in the two tanks when the valve is opened? Assume 100% yield and zero volume for the connecting valve and tube. (Do not round off until the end of your calculations. Express your answers to 2 significant figures.) 10