1. What volume of water is required to make a 4.65 M solution from 5.2 g of NaBr (MM = g/mol)?

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1 CHEMISTRY 110 EXAM II Answer Key March 22, What volume of water is required to make a 4.65 M solution from 5.2 g of NaBr (MM = g/mol)? A ml B ml C. 11 ml D. 235 ml E. 240 ml 2. The distinguishing characteristic of all electrolytic solutions is that they A. contain molecules. B. conduct electricity. C. do not conduct electricity. D. react with other solutions. E. always contain acids. 3. Which ionic solid is soluble in water? A. Hg 2 Cl 2 B. Sr(NO 3 ) 2 C. BaCO 3 D. CaSO 4 E. Cu 3 (PO 4 ) 2 are soluble in water 4. An automobile tire is filled with air at a pressure of 30.0 psi (pressure per square inch) at 22 C. A cold front moves through and the temperature drops to 7.0 C. Assuming no change in volume, what is the new tire pressure in psi? A psi B psi C psi D psi E psi 5. Calculate the volume of 64.4 g of nitrogen (MM = g/mol) gas at STP? A L B L C L D. 103 L E. none of the above 6. Ammonia (NH 3 ) burns in oxygen gas to form nitrogen monoxide and water vapor. How many volumes of NO gas are obtained from one volume of ammonia at the same temperature and pressure? Hint: write an equation. A. 1 B. 2 C. 3 D. 4 E. none of the above

2 7. A bottle was found in lab containing a silver colored metal. The unknown substance was thought to be magnesium, manganese, mercury or molybdenum. The metal was identified by experiment. If 12.4 g of the metal is at an initial temperature of 25.0 C and reaches a final temperature of 40.0 C when 88 J is supplied, identify the material? Metal Specific Heat (J/g C) magnesium 1.05 manganese 0.48 mercury 0.14 molybdenum 0.25 A. magnesium B. manganese C. mercury D. molybdenum E. metal cannot be identified 8. The reaction below was demonstrated in class. Which of the following statements are true? Ba(OH) 2 8 H 2 O(s) + 2 NH 4 Cl(s) BaCl 2 (aq) + 2 NH 3 (g) + 10 H 2 O(l) H = kj I. The reaction is exothermic. II. The enthalpy change would be different if gaseous vapor were produced. III. The enthalphy change would be 290. kj if 2 moles of barium hydroxide octahydrate where used. IV. The reaction can be classified as a precipitation reaction. A. I B. II C. III D. I and II E. II and III G. I, II and III H. II, III and IV Problems (60 pts) 9. (10 pts) Complete and balance the following molecular equation. In addition, write the net ionic equation. For full credit, indicate the state of each product as (s), (l), (g) or (aq). a. (NH 4 ) 2 SO 3 (aq) + 2 KCl(aq) K 2 SO 3 (aq) + 2 NH 4 Cl(aq) Net Ionic: none b. If a 25.0 ml of a 4.4 M ammonium sulfite solution is reacted with 50.4 ml of a 2.2 M potassium chloride solution, calculate the amount (g) of precipitate formed? No precipitate, 0 grams

3 10. (10 pts) Complete and balance the following molecular equation. In addition, write the net ionic equation. For full credit, indicate the state of each product as (s), (l), (g) or (aq). a. 2 HI (aq) + Mg(OH) 2 (aq) MgI 2 (aq) + 2 H 2 O (l) Net Ionic: H + (aq) + OH - (aq) H 2 O (l) b. Calculate the volume (L) of 6.0 M iodic acid solution needed to neutralize 50. ml sample of a 6.4 M magnesium hydroxide solution L 11. (12 pts) Assign oxidation numbers for each of the following atoms/ions in the redox reaction given below and answer the following questions. a. Oxidation Number (put oxidation number on the space provided for each atom below.) 4 FeCl 2 (aq) + O 2 (aq) + 4 HCl (aq) 4 FeCl 3 (aq) + 2 H 2 O (l) b. Which atom is being oxidized? Fe c. Which molecule/ion is the oxidizing agent? O (15 pts) Potassium chlorate (MM = g/mol) was decomposed by the following reaction. 2 KClO 3 (s) 2 KCl (aq) + 3 O 2 (g) The oxygen produced was collected over water at 328 K at a total pressure of 734 torr. The volume of gas collected was 1.20 liters. Note: Vapor Pressure of Water table can be found on the periodic table page. a. Calculate the partial pressure of O 2 in the gas collected. 616 torr b. Calculate the mass (g) of potassium chlorate in the sample that was decomposed g

4 13. (8 pts) A balloon was found floating over the Behrend campus yesterday. The atmospheric pressure was known to be 742 mm Hg and the temperature was 4.2 ºC. The balloon contained 3.23 moles of gas. a. If the balloon contained g of gas, calulate the density (g/ml) of the gas inside the balloon g/ml b. Using the table below, what gas was contained in the balloon? Helium Substance Density (g/ml) hydrogen helium air carbon dioxide (5 pts) A sample of titanium metal is heated to C and dropped into 50.0 g of water initially at 25.0 C. Assuming that all the heat lost by the titanium is absorbed by the water; calculate the mass of titanium if the final temperature reaches 29.2 C. The specific heat of water is J/g C and titanium is J/g C. 25 g

5 Important Constants Solubility Rules (apply in order) R = L-atm/mole-K 1. All Na +, K +, and NH + 4 salts are soluble. 1 atmosphere = psi 2. All NO - 3, C 2 H 3 O - 2, ClO - 3, and C1O - 4 salts are soluble. 1 atmosphere = 760 torr (exactly) 3. All Ag +, Pb 2+ 2+, and Hg 2 salts are insoluble. 1 atmosphere = 760 mm Hg (exactly) 4. All Cl -, Br -, and I - salts are soluble. density of H 2 O = 1.00 g/ml 5. All CO 2-3, O 2-, S 2-, OH -, SO 2-3, CrO 2-4, Cr 2 O , and PO 4 specific heat H 2 O = J/gºC salts insoluble, except CaS, SrS, BaS and Ba(OH) 2. specific heat Ti = J/g C 6. All SO 2-4 salts are soluble except Ca 2+, Sr 2+, and Ba 2+. Vapor Pressure of Water at Various Temperatures T ( o C) P (torr) T ( o C) P (torr) T ( o C) P (torr) T ( o C) P (torr)