Midterm Examination 2

Transcription

1 CH 221 General Chemistry Spring 2012 Name: Midterm Examination 2 Useful Information is located on the last two pages of the Exam. Multiple Choice Questions A carton of Morton's Iodized Salt, NaCl with traces of potassium iodide, has a reported mass of 26 oz (737g). 1. Assuming the sample is nearly pure NaCl, how many moles of NaCl are in the carton? a) mole NaCl b) 1.93 mole NaCl c) 7.85 mole NaCl d) 12.6 mole NaCl 2. How many formula units of NaCl are contained in the carton? a) 2.3 x NaCl formula units b) 7.6 x NaCl formula units c) 6.7 x NaCl formula units d) 3.5 x NaCl formula units 3. How many atoms are contained in the carton? a) 2.3 x atoms b) 6.8 x atoms c) 1.5 x atoms d) 3.7 x atoms 4. Suppose I synthesize 0.35 mole of Cuprous Chloride, CuCl. What mass of product has been obtained? a) 2.56 g b) 34.7 g c) 54.2 g d) 103 g

2 5. What is the percentage by mass Carbon in Morphine, C 17 H 19 NO 3? a) 45.2% b) 62.7% c) 71.6% d) 88.4% 6. Hydrazine is an extremely combustible compound composed of Nitrogen and Hydrogen that is used as a fuel for ICBM's. This compound has a composition of 87.42% Nitrogen and 12.58% Hydrogen. What is the Empirical Formula of hydrazine? a) N 2 H 2 b) NH 2 c) N 2 H d) NH 7. Which of the following is not an acid: a) H 2 SO 4 b) NaCl c) HNO 3 d) H 3 PO 4 8. What salt is produced when Nitric Acid (HNO 3 ) is neutralized by Potassium Hydroxide (KOH)? a) KH b) KNO 3 c) H 2 O d) HONO 3 9. When Cesium Ion combines with Phosphate Ion, the resulting compound will have the following chemical formula: a) Cs 3 PO 4 b) Cs 2 PO 4 c) Cs(PO 4 ) 2 d) Cs(PO 4 ) 3

3 10. When elemental Calcium combines with elemental Fluorine, the resulting compound is expected to have a chemical formula of: a) CaF b) Ca 2 F c) CaF 2 d) Ca 2 F The charge on the cation in MnO 2 is: a) Mn + b) Mn 2+ c) Mn 3+ d) Mn What is the Oxidation State of the Sulfur in H 2 SO 4? a) S 2+ b) S 4+ c) S 6+ d) S What is the Oxidizing Agent in the following chemical reaction: N 2 (g) + 3 H 2 (g) 2 NH 3 (g) a) N 2 b) H 2 c) NH ml of a 6.5 M solution is diluted to 250 ml. What is the concentration of the diluted solution? a) 1.5 M b) 0.26 M c) M d) M

4 15. What volume of a 6.0 M stock NaOH solution is required to prepare 400 ml of 1 M NaOH? a) 15.0 ml b) 33.3 ml c) 42.1 ml d) 66.7 ml 16. Determine H o at 298K for the following reaction: 2 Cl 2 (g) + 2 H 2 O(l) 4 HCl(g) + O 2 (g) Useful Data: Cmpd H o f (298) [kj/mol] H 2 O(l) HCl(g) a) kj/mol b) 57.6 kj/mol c) kj/mol d) kj/mol

5 Short Answer Questions 1. Neutralization is a reaction between "equivalent" amounts of Acid and Base to produce a neutral aqueous solution. Consider the neutralization of Sulfuric Acid by the Base Sodium Hydroxide: H 2 SO 4 (aq) + 2 NaOH(aq) Na 2 SO 4 (aq) + 2 H 2 O 45.7 ml of M H 2 SO 4 is required to completely neutralize an NaOH solution. How many grams of NaOH were required to carry-out this neutralization? 2. Hydrogen Cyanide, HCN, can be made in a two step process. First, Ammonia is reacted with Oxygen to give Nitrogen Oxide: 4 NH 3 (g) + 5 O 2 (g) 4 NO(g) + 6 H 2 O(g) Then, Nitrogen Oxide is reacted with Methane, CH 4 : 2 NO(g) + 2 CH 4 (g) 2 HCN(g) + 2 H 2 O(g) + H 2 (g) We wish to prepare Hydrogen Cyanide from the available 24g of Ammonia and 25g of Methane. a) How much Nitrogen Oxide can theoretically be produced in the first reaction. b) How many grams of Hydrogen Cyanide can theoretically be produced?

6 3. Identify the products of the following reaction. Identify any products which may precipitate. Write the Total and Net Ionic Equations for this reaction. AgNO 3 (aq) + MgCl 2 (aq) 4. A 30.5g sample of an alloy at 93.0 o C is placed into 55.0g of Water at 22.0 o C in an insulated coffee cup calorimeter. I the final temperature of the system is 31.4 o C, what is the Specific Heat of the alloy? Assume the calorimeter absorbs no heat.

7 5. Determine H o for the conversion of Diamond into Graphite: C(diamond) C(graphite) Useful Data C(diamond) + O 2 (g) CO 2 (g) H o = kj C(graphite) + O 2 (g) CO 2 (g) H o = kj

8 Appendix - Useful Data Constants Avogadro's Number N A = 6 x entities / mole Solubility Rules for Ionic Compounds Substances Solubility Common Exceptions Alkali metals and Soluble None Ammonium compounds Nitrates, Acetates, Chlorates, and Perchlorates Chlorides, Bromides, and Iodides Soluble Soluble None Ag + and Hg 2 2+ halides and Hg 2+ iodides are insoluble. PbCl 2, PbBr 2, PbI 2 and HgBr 2 are slightly soluble. Sulfates Soluble Sr 2+, Ba 2+, Pb 2+ and Hg 2 2+ sulfates are insoluble. CaSO 4 and Ag 2 SO 4 sulfate are slightly soluble. Hydroxides Insoluble Alkali metal and Ba 2+ hydroxides are soluble. Sr(OH) 2 and Ca(OH) 2 are slightly soluble. Sulfides, Carbonates, Phosphates Insoluble Alkali metal and NH 4 + compounds are soluble. CaS, SrS and BaS are soluble.