Chemistry 2 Summer 2008 Exam 2 Chapters 6(part), 7-10

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1 Name Chemistry 2 Summer 2008 Exam 2 Chapters 6(part), 7-10 Answer the following by writing the word, words, letter, letters or number in each blank that best completes each sentence. (1 point each) 1. A(n) is a substance that is incompletely ionized in water due to the reversibility of the reaction that forms hydronium ions, H 3 O +, in water. They yield significantly less than one H 3 O + ion in solution for each acid molecule dissolved in water. 2. A(n) is a group represented by a substance s chemical formula that is, a group containing the kinds and numbers of atoms or ions listed in the chemical formula. It is a general term that can be used in reference to elements, molecular compounds, or ionic compounds. 3. A(n) is a chemical formula that includes positive integers that describe the simplest ratio of the atoms of each element in a compound. 4. A(n) is a mixture whose particles are so evenly distributed that the relative concentrations of the components are the same throughout. Solutions can also be called homogeneous mixtures. 5. A(n) is a chemical equation for which the spectator ions have been eliminated, leaving only the substances actively involved in the reaction. 6. A(n) change is a change that leads to heat energy being released from the system to the surroundings. 7. A(n) is a substance that generates at least one hydroxide ion in solution for every unit of substance added to water. 8. is any chemical change in which at least one element loses electrons, either completely or partially. 1

2 9. A(n) is the electrode at which oxidation occurs in a voltaic cell. It is the source of electrons and is the negative electrode. 10. A(n) is the portion of a voltaic cell that allows ions to flow. 11. A(n) is a battery that is not rechargeable. 12. is the process by which a redox reaction is pushed in the nonspontaneous direction or the process of applying an external voltage to a voltaic cell, causing electrons to move from what would normally be the cell s cathode toward its anode. Answer the following by writing one of these words or phrases in each blank. (1/2 point each) 10-fold heat rarely above higher red acceptor homogeneous mixture reduced acidic ions reduction amphoteric isotopes released basic less than 7 single blue light solute complete formula lower solvent continuous molecules sour delta, Δ oxidation transfer donor oxidized water greater than 7 2

3 13. Any substance that has a(n) taste is an acid. 14. On the basis of the Arrhenius definitions, a(n) solution is a solution with a significant concentration of H 3 O The chemical equations for completion reactions are written with arrows to indicate that the reaction proceeds to form almost 100% products. 16. The molecular mass of the compound is the weighted average mass of the compound s naturally occurring. 17. If special conditions are necessary for a reaction to take place, they are often specified the arrow in the reaction s chemical equation. 18. To indicate that a chemical reaction requires the addition of heat in order to proceed, we place an upper-case Greek above the arrow in the reaction s chemical equation. 19. A solution, also called a(n), is a mixture whose particles are so evenly distributed that the relative concentrations of the components are the same throughout. 20. In solutions of solids dissolved in liquids, we call the solid the and the liquid the. 21. In a complete ionic equation, which describes the forms taken by the various substances in solution, the ionic compounds dissolved in the water are described as, and the insoluble ionic compound is described with a(n). 22. If in a chemical reaction, more energy is released in the formation of new bonds than was necessary to break old bonds, energy is overall, and the reaction is exergonic. 23. A solution that has a significant concentration of hydroxide ions is called a(n) solution. 3

4 24. Acidic solutions have ph values, and the more acidic a solution is, the its ph. A change of 1 ph unit reflects a(n) change in H 3 O ion concentration. Basic solutions have ph values, and the more basic the solution is, the its ph. 25. Litmus, a natural dye, is derived from lichen. It turns in acidic conditions and in basic conditions. 26. When hydronium ions and hydroxide ions collide in solution they react to form. 27. A Brønsted-Lowry acid is a proton (H + ), a Brønsted-Lowry base is a proton, and a Brønsted-Lowry acid-base reaction is a proton. 28. A substance that can act as either a Brønsted-Lowry acid or a Brønsted-Lowry base, depending on the circumstances, is called a(n) substance. 29. Electrons are found unattached to atoms. Thus, for one element or compound to lose electrons and be, another element or compound must be there to gain the electrons and be. In other words, (loss of electrons) must be accompanied by (gain of electrons). 30. In a combustion reaction, oxidation is very rapid and is accompanied by and usually. 31. Balance the following equations. (4 points) a. SCl 2 (l) + NaF(s) S 2 Cl 2 (l) + SF 4 (g) + NaCl(s) b. H 2 O(g) + NO(g) O 2 (g) + NH 3 (g) 4

5 32. For each of the following pairs of formulas, predict whether the substances they represent would react in a precipitation reaction. If there is no reaction, write, No Reaction. If there is a reaction, write the complete equation for the reaction. (6 points) a. NaOH(aq) + Zn(NO 3 ) 2 (aq) b. CuSO 4 (aq) + LiNO 3 (aq) c. Pb(C 2 H 3 O 2 ) 2 (aq) + Na 2 SO 4 (aq) 33. Classify each of the following substances as a weak acid, strong acid, weak base, or strong base in the Arrhenius acid-base sense. (3 points) a. HNO 3 b. ammonia c. LiOH d. phosphorous acid e. H 2 SO 4 f. NaHCO Write the complete, balanced equation for the combustion of the thioester, C 4 H 9 COSC 2 H 5 (l). (4 points) 5

6 35. Write the complete equation for the neutralization reactions that take place when the following are mixed. (If an acid has more than one acidic hydrogen, assume that there is enough base to remove all of them. Assume that there is enough acid to neutralize all of the basic hydroxide ions.) (4 points) a. H 3 PO 4 (aq) + KOH(aq) b. HI(aq) + CaCO 3 (s) 36. Sodium perbromate is an oxidizing agent that can be made in the reaction shown below. Write the oxidation number for each atom in the equation above its symbol in the equation. Identify which substance is oxidized, which substance is reduced, the oxidizing agent, and the reducing agent. (8 points) NaBrO3 + F2 + 2NaOH NaBrO4 + 2NaF + H2O Oxidized Reduced Oxidizing agent Reducing agent For the following numerical problems, be sure to show your work and put a box around your answer. 37. Manganese metal is produced from the manganese(iii) oxide, Mn 2 O 3, which is found in manganite, a manganese ore. How many kilograms of manganese are in Mg of Mn 2 O 3? (5 points) 6

7 38. Uranium is distributed in a form called yellow cake, which is made from uranium ore. In the second step of the reactions that form yellow cake from uranium ore, uranyl sulfate, UO 2 SO 4, is converted to (NH 4 ) 2 U 2 O 7. 2UO 2 SO 4 + 6NH 3 + 3H 2 O (NH 4 ) 2 U 2 O 7 + 2(NH 4 ) 2 SO 4 a. What is the maximum mass, in kilograms, of (NH 4 ) 2 U 2 O 7 that can be formed from the reaction of 100 kg of water with 481 kg of UO 2 SO 4 and an excess of ammonia? (5 points) b. If you were planning this reaction, explain why you would add water in excess and make (NH 4 ) 2 U 2 O 7 is limiting. (4 points) 39. What volume of 3.00 M nitric acid, HNO 3, would be necessary to neutralize and dissolve 2.56 kg of solid cadmium hydroxide, Cd(OH) 2? (5 points) Answer the following in short answer form. (4 points each) 40. Describe how the weak monoprotic acid hydrofluoric acid, HF (used in aluminum processing) acts when it is added to water, including a description of the nature of the particles in solution before and after the reaction with water. If there is a reversible reaction with water, describe the forward and the reverse reactions. 7

8 41. Describe the process for dissolving the ionic compound lithium iodide, LiI, in water, including the nature of the particles in solution and the attractions between the particles in the solution. 42. Black-and-white photographic film has a thin layer of silver bromide deposited on it. Wherever light strikes the film, silver ions are converted to uncharged silver atoms, creating a dark image on the film. Consider the precipitation reaction that takes place between water solutions of silver nitrate, AgNO 3 (aq), and sodium bromide, NaBr(aq), to form solid silver bromide, AgBr(s), and aqueous sodium nitrate, NaNO 3 (aq). a. Describe the mixture after the silver nitrate and sodium bromide solutions are mixed but before the reaction takes place. b. Describe the reaction. c. Describe the mixture after the reaction is complete. 8

9 43. Consider the reaction between the strong acid nitric acid, HNO 3 (aq), and the strong base potassium hydroxide, KOH(aq), forming water and potassium nitrate, KNO 3 (aq). a. Describe the mixture after the nitric acid and potassium hydroxide solutions are mixed but before the reaction takes place. b. Describe the reaction. c. Describe the mixture after the reaction is complete. 44. Give four reasons why the actual yield in a chemical reaction is less than the theoretical yield. 9