Chem 177 Exam II March 3, Teaching Assistants and Recitation Sections. Page Points Score Name Sections Time Stacey Althaus 5 10:00 2

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1 Dr. Joe Burnett Spring 2010 This exam consists of 13 questions on 9 pages Chem 177 Exam II March 3, 2010 Name Recitation TA Recitation Section Grading Teaching Assistants and Recitation Sections Page Points Score Name Sections Time Stacey Althaus 5 10: pts 14 pts 24 pts Kyle Marchuk Kristopher McKee Justin Smith Anthony Stender 1, 10 11, , 3 8:00, 1:10 2:10, 1:10 12:10 8:00, 9: pts 16 pts Nishad Thamban Chandrika Songchen Xu 4, 6 7, 9 9:00, 11:00 11:00, 12:10 7 TOTAL 12 pts 104 pts Questions are written on both sides of each page. There is a periodic table and an equation on the last page. You may remove this page for scratch paper. Show all work. Answers should include appropriate units and contain the correct number of significant figures. The last day to drop Chem 177 and add Chem 50 is Thursday, March 4, at 4:00 PM. See your advisor to obtain the drop/add form and go to the General Chemistry Office, room 1608 Gilman Hall.

2 2 1. (2 pts) Which of the following is a strong electrolyte? a) HCl(aq) b) H 2 O c) acetic acid d) ammonia e) all of the above are strong electrolytes 2. (6 pts) Consider an aqueous solution of acetic acid, write the formulas of all species expected to be present (other than H 2 O). Circle the substance present at the highest concentration in the solution. 3. (4 pts) What is the oxidation state of the sulfur atom in the metabisulfite ion S 2 O 5 2? 4. (4 pts) Write the reaction equation that represents what happens when ammonia NH 3 is dissolved in water. [Hint: what type of aqueous solution results from the dissolution of NH 3?] For full credit, indicate the phases of all reactants and products (aq, l, s, g). 5. (8 pts) How many liters of 0.23 molar NaOH is needed to neutralize 2.63 liters of 0.49 molar EDTA. EDTA is a weak acid that can donate four protons H + and is symbolized in the following equation as H 4 Y. For full credit, show all work, use units, and report your answer to the correct number of significant figures. 4 NaOH(aq) + H 4 Y 4 H 2 O(l) + Na 4 Y(aq)

3 3 6. (14 pts) In 1847, the Italian scientist Ascanio Sobrero first synthesized nitroglycerin, the explosive agent in dynamite. Nitroglycerin C 3 H 5 (NO 3 ) 3 is produced by the reaction of glycerin C 3 H 5 (OH) 3 and nitric acid: C 3 H 5 (OH) HNO 3 C 3 H 5 (NO 3 ) H 2 O What is the theoretical yield in grams of nitroglycerin that can be formed when 251 g of glycerin C 3 H 5 (OH) 3 is added to 2.00 liters of 6.00 Molar HNO 3 (aq)? For full credit, show all work, use units, and report your final answer to the correct number of significant figures. Limiting reactant: theoretical yield of nitroglycerin grams substance C 3 H 5 (OH) 3 glycerin HNO 3 nitric acid C 3 H 5 (NO 3 ) 3 nitroglycerin H 2 O water molar mass g/mol

4 7. Nitroglycerin is a shock sensitive explosive and decomposes according to the following reaction: 4 4 C 3 H 5 (NO 3 ) 3 12 CO 2 (g) + 10 H 2 O(g) + 6 N 2 (g) + O 2 (g) ΔH = 5811 kj A. (4 pts) This reaction is. a) endothermic b) exothermic c) neither exothermic nor endothermic B. (2 pts) This reaction is reaction. a) a redox or oxidation reduction b) metathesis c) a neutralization d) a combination e) none of the above C. (4 pts) When nitroglycerin detonates under typical room temperature and pressure conditions,. a) work is done by the reaction on the surroundings b) work is done on the reaction by the surroundings c) no work occurs D. (2 pts) For the decomposition of nitroglycerin, the magnitude of ΔH is than that of ΔE. a) greater than b) less than c) equal to E. (4 pts) Briefly but completely explain your answer to the last question. F. (8 pts) Calculate the heat transferred (q) when 454 g of nitroglycerin decomposes. Report your answer in kilojoules kj. For full credit show all work, use units, and report your answer to the correct number of significant figures. Reporting your answer with the correct sign will be awarded 1 extra credit point. answer: kj

5 5 8. (8 pts) Calculate the molar concentration of potassium ions K + in a solution formed from mixing 10.0 ml of 0.10 Molar K 3 PO 4 (aq) with 10.0 ml of 0.10 Molar K 2 SO 4 (aq). Assume that the volumes are additive. For full credit, show all work, use units, and report your answer to the correct number of significant figures. Please report your final answer in the box. [K + (aq)] = 9. (6 pts) When 1.00 g of H 2 reacts with 1.00 g of O 2 to form water, O 2 is the limiting reactant. What is the mass amount of excess H 2 in grams? For full credit, show all work, use units, and report your answer to the correct number of significant figures. 2 H 2 (g) + O 2 (g) 2 H 2 O(l) answer: grams

6 6 10. (12 pts) Complete and balance the following reaction equations. For full credit, include the phase of all reacting substances (s, l, g, or aq). If no reaction is expected to occur, write, no reaction. A. (NH 4 ) 2 S(aq) + AgNO 3 (aq) B. HCl(aq) + NaNO 3 (aq) C. + KOH(aq) K 2 SO 4 (aq) + H 2 O(l) 11. (4 pts) Write the net ionic equation for the following reaction. For full credit, include the phase of all substances (s, l, g, or aq). 2 HClO 3 (aq) + Ba(OH) 2 (aq) Ba(ClO 3 ) 2 (aq) + 2 H 2 O(l)

7 12. (8 pts) When 50.0 ml of 1.00 Molar HNO 3 and 50.0 ml of 1.00 Molar NaOH are combined in a constant pressure calorimeter, the temperature increases by 6.69 o C. The total solution mass is g and you may assume that the solution has the same specific heat as water, 4.18 J/g- o C. 7 What is the enthalpy change of the reaction: HNO 3 (aq) + NaOH(aq) H 2 O(l) + NaNO 3 (aq)? Note that the moles of HNO 3 and NaOH that are combined are identical and stoichiometric; exactly enough HNO 3 is added to react with the NaOH ml of a 1.00 Molar solution contains moles of solute. For full credit, show all work, and report your answer to the correct number of significant figures. answer: kj 13. (4 pts) Using the following information 2 CO(g) 2 C(s) + O 2 (g) ΔH = +222 kj What is the enthalpy of reaction of the following reaction? C(s) O 2(g) CO(g) ΔH =? For full credit show all work, use units, and report your answer to the correct number of significant figures. answer: kj

8 8 Chem 177 Periodic Table Exam II

9 9 1 cal = joules specific heat = sp. ht. = q mass in g ΔT q = sp.ht. m ΔT = c s m ΔT ΔE = C v ΔT Substance Molar Mass H g/mol O g/mol H 2 O 18.0 g/mol density of water at 25 o C: 1.00 g/ml specific heat of water: 4.18 J g o C