6. From the data given in Handout 1 on the class website, determine the best weak acid conjugate base pair to prepare a buffer of ph = 9.00.

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1 EXTRA REVIEW 2A 1. A solution is prepared by mixing 80.0 ml of a 0.50 M nitrous acid solution and 20.0 ml of a 0.25 M sodium nitrite solution. Will this be a buffer solution? Calculate the ph. Is this solution acidic or basic? 2. A solution is prepared by mixing 80.0 ml of a 0.50 M nitrous acid solution and 20.0 ml of a 0.25 M sodium hydroxide solution. Will this be a buffer solution? Calculate the ph. Is this solution acidic or basic? 3. A solution is prepared by mixing 50.0 ml of a 0.45 M pyridine (C 5 H 5 N) solution and 25.0 ml of a 0.60 M pyridine hydrochloride (C 5 H 5 NH + Cl - ) solution. Will this be a buffer solution? Calculate the ph. Is this solution acidic or basic? 4. A solution is prepared by mixing 50.0 ml of a 0.45 M pyridine solution and 50.0 ml of a 0.60 M hydrochloric acid solution. Will this be a buffer solution? Calculate the ph. What will be the concentration of the chloride ions in the solution? 5. A solution is prepared by mixing 50.0 ml of a 0.45 M pyridine solution and 25.0 ml of a 0.60 M hydrochloric acid solution. Will this be a buffer solution? Calculate the ph. Is this solution acidic or basic? 6. From the data given in Handout 1 on the class website, determine the best weak acid conjugate base pair to prepare a buffer of ph = Calculate the molar ratio of base to conjugate acid in a solution that has a ph of and contains the base ethylamine (C 2 H 5 NH 2 ) and a salt of its conjugate acid, ethylamine hydrochloride (C 2 H 5 NH 3 + Cl - ). *8. Determine the volumes of 1.0 M NaX, 1.0 M HCl, and water needed to produce ml of a buffer that is 0.20 M HX and 0.30 M NaX. *9. Determine the volume of 1.0 M NaOH that must be mixed with 50.0 ml of 0.20 M HX to produce a buffer with ph = 6.

2 EXTRA REVIEW 2B 1. A solution is 0.45 M in cyanic acid (HOCN) and 0.20 M in sodium cyanate (NaOCN). The K a for cyanic acid is 3.5 x (a) Calculate the ph of the solution. Is the solution acidic or basic? (b) Calculate the final ph if 0.10 gram of sodium hydroxide is added to 1.00 liter of the buffer solution, assuming ther volume does not change. (c) Calculate the final ph if 0.50 gram of sodium hydroxide is added to1.00 liter of the buffer instead of 0.10 gram, still assuming the volume does not change. 2. A buffer is prepared by mixing 30. ml of a 1.5 M hydrofluoric acid solution with 20. ml of a 2.0 M sodium fluoride solution. (a) Calculate the ph of the solution. Is the solution acidic or basic? (b) Calculate the final ph if 5 ml of a 1.0 M hydrochloric acid solution is added to the buffer. (c) Calculate the final ph if 5.0 ml of a 1.0 M sodium hydroxide solution is added to the buffer solution instread of the hydrochloric acid solution. EXTRA REVIEW 2C 1. Hydrazine (N 2 H 4 ) is a weak organic base that reacts with water as follows: N 2 H 4 + H 2 O N 2 H OH - The base dissociation constant for this reaction, K b = 1.7 x When titrated with hydrochloric acid, hydrazine reacts as follows: N 2 H 4 + HCl N 2 H Cl - (a) 50.0 ml of a M solution of hydrazine are titrated with M hydrochloric acid. Calculate the volume of the hydrochloric acid solution required to neutralize the hydrazine. (b) Calculate the ph of the hydrazine solution at the beginning of the titration. (c) Calculate the ph of the resulting solution after 5.00 ml of the hydrochloric acid solution has been added. (d) Calculate the ph of the resulting solution after ml of the hydrochloric acid solution has been added. (e) Calculate the ph of the resulting solution at the equivalence point. (f) Calculate the ph of the resulting solution after ml of the hydrochloric acid solution has been added. (g) Sketch the titration curve for the titration of M hydrazine with M hydrochloric acid. Plot accurately the ph at the beginning of the titration, and after the addition of 5.00 ml, ml, ml, and 25.0 ml of the M hydrochloric aicd. (h) From the list of indicators in Figure 15.8, what would be the best indicator for this titration? (continued on next page)

3 2. The titration curve for a weak diprotic acid, H 2 X, being titrated with a strong base is shown. Indicate the following. (a) The point on the titration curve when the solution contains only H 2 X (b) The point on the titration curve when the solution contains equal amounts of H 2 X and HX - (c) The point on the titration curve when the solution contains only HX - (d) The point on the titration curve when the solution contains equal amounts of HX - and X 2- (e) The point on the titration curve when the solution contains only X 2- (f) The K a1 of the weak diprotic acid and the K a2 of the weak diprotic acid (g) From Table 15.8 in the textbook, determine the best indicator to use in order to signal the first equivalence point for this titration (h) From Table 15.8 in the textbook, determine the best indicator to use in order to signal the second equivalence point for this titration *3. For a titration between 10.0 ml of 0.20 M HX and 0.10 M NaOH: (a) Determine the ml of the NaOH solution needed to reach the equivalence point (b) Determine the ph of the 0.20 M HX solution before the titration (c) Determine the ph of the solution after the addition of 5.0 ml of NaOH (d) Determine the ph of the solution after the addition of 10.0 ml of NaOH (e) Determine the ph of the solution after the addition of 15.0 ml of NaOH (f) Determine the ph of the solution after the addition of 20.0 ml of NaOH (g) Determine the ph of the solution after the addition of 25.0 ml of NaOH (h) Determine the acid ionization constant for HX (i) Determine the best indicator for this titration from the indicators in Table 15.8 *4. A student titrated a spoonful of an unknown monoprotic acid with an NaOH solution of unknown concentration. After adding 5.00 ml of base, he found the ph of the solution to be 6.0. The equivalence point came when 7.00 ml of additional base was added. Calculate the ionization constant of the acid. *5. Clinicians are frequently required to determine the bicarbonate concentration in human blood since the HCO 3 - concentration, along with that of dissolved CO 2, affects the ph of the blood. The HCO 3 - concentration is easily determined by titimetry employing an excess of HCl, which is back-titrated with NaOH. Write equations for the two reactions, and calculate the HCO 3 - concentration in a 0.10 ml serum sample that requires addition of 1.00 ml of M HCl followed by back-titrating with 0.76 ml of M NaOH.

4 EXTRA REVIEW 2D 1. The solubility of tin (II) fluoride in water is grams per liter at 20ºC. Calculate the solubility product, K sp, for this salt at 20ºC. 2. Look up the solubility product constants for silver hydroxide, manganese (II) hydroxide, and chromium (III) hydroxide, and determine which salt is most soluble in water. 3. Using data from Handout 2 on the class website: (a) Calculate the solubility of cobalt (II) sulfide, in moles per liter and grams per liter, in pure water at 25ºC. (b) Calculate the solubility of cobalt (II) sulfide, in moles per liter and grams per liter, in a solution that is 0.10 M Na 2 S at 25ºC. 4. A solution is made 0.10 M in Ba(NO 3 ) 2, and 0.05 M in NaF. Will BaF 2 precipitate? *5. At 20ºC, the solubility product, K sp, for cadmium phosphate is 2.5 x (a) Calculate the cadmium ion concentration in a solution of cadmium phosphate in pure water at 20ºC. (b) Calculate the cadmium ion concentration in a 0.10 M phosphate ion solution at 20ºC. *6. At 20ºC, the solubility product, K sp, for silver chromate is 1.9 x (a) Calculate the silver ion concentration in a solution of silver chromate in pure water at 20ºC. (b) Calculate the silver ion concentration in a 0.10 M chromate ion solution at 20ºC. EXTRA REVIEW 2E 1. Calculate the concentration of nickel (II) ions needed to precipitate nickel (II) hydroxide in a buffer solution of ph A solution is made 0.30 M in Ca 2+, and NaOH is added until the OH - concentration is M. Calculate the percentage of Ca 2+ ions left in the solution at this point. 3. Phosphate ions are slowly added to a solution containing M calcium ions and M silver ions. (a) What cation will be the first to precipitate? (b) What will be the concentration of the phosphate ions when the first cation starts to precipitate? (c) What will be the concentration of the first cation when the second cation starts to precipitate? 4. In the precipitation of metal sulfides, selective precipitation can be achieved by adjusting the hydrogen ion concentration. Calculate the ph that CoS begins to precipitate from a water solution saturated with H 2 S (0.077 M) and containing 0.08 M Co Calculate the solubility of ZnS at ph and at ph 0.00 in a water solution saturated with H 2 S (0.077 M). *6. A solution is made 0.10 M in Mg 2+, 0.10 M in NH 3, and 1.0 M in NH 4 Cl. Will Mg(OH) 2 precipitate? *7. Calculate the solubility of Mg(OH) 2 at ph 2.0 and at ph 12.0 in a water solution.

5 EXTRA REVIEW 2F 1. Find the Chart of the Nuclides on the internet at the web site for the National Nuclear Data Center, and complete the following data for data concerning all known isotopes of neon. Isotope Stable or Radioactive Natural Abundance Half-Life Decay Mode 2. Complete the following nuclear equations and supply symbols of values for X or x. (a) 19 9X + 1 xh 16 8X + 4 XX (b) 176 XLu X XX + X -1β - (c) X XC 11 XX β + (d) X XS + 0-1e X (e) 26 XMg + 1 0n 4 Xα + X XX (f) 16 8X + 2 1X 14 7X + 4 XX 3. Write equations for each of the following nuclear processes. (a) beta positive decay by 70 32Ge (b) beta minus decay by 80 35Br (c) alpha decay by Fr (d) electron capture by 26 14Si 4. What type of decay would you expect from each of the following radioisotopes? (a) 3 H (b) 105 Ag (c) 236 U

6 EXTRA REVIEW 2G 1. Radioactive 123 I, which as a half-life of 13.2 hours is used for diagnostic study of thyroid diseases. How many days will it take for the radioactivity to fall to 5.00% of its original intensity? 2. If g of 60 Co decays by β - emission to g in 21 years, what is the half-life of 60 Co? 3. A sample of a radioisotope shows an activity of 161. disintegrations per minute. After 45.0 minutes, the activity decreases to 53 disintegrations per minute. Determine the half-life of the radioisotope. 4. In the skeleton of a fish caught in French Polynesia in 2005, the 14 C disintegration rate was 17.2 cpm g -1 of carbon. Calculate the age of the fish. How can this be? What does this imply about South Pacific archaeology? 5. In a sample of zircon from the Jack Hills of Western Australia, the mass of Pb is 84.4% the mass of the U present. Estimate a minimum age for the earth from this information. 6. Calculate the binding energy per nucleon for the following nuclear species. (a) 32 16S (m = u) (b) 16 8O (m = u) *7. The half-lives of 235 U and 238 U are 7.1 x 10 8 years and 4.5 x 10 9 years respectively. Presently, uranium is 99.28% 238 U and 0.72% 235 U. Calculate the percent natural abundance of each uranium isotope when the earth was formed 4.5 billion years ago. *8. The half-lives of 235 U and 238 U are 7.1 x 10 8 years and 4.5 x 10 9 years respectively. Presently, uranium is 99.28% 238 U and 0.72% 235 U. Calculate the percent natural abundance of each uranium isotope in 1.0 billion years from now. EXTRA 2A ANSWERS 1. yes, 2.49, acidic 2. yes, 2.55, acidic 3. yes, 5.41, acidic 4. no, 1.12, acidic, M Cl - 5. yes, 4.93, acidic 6. HCN and CN * ml 1.0 M NaX, 20.0 ml 1.0 M HCl, 30.0 ml H 2 O *9. 2 ml

7 EXTRA 2B ANSWERS 1. (a) 3.10, acidic (b) 3.11 (c) (a) 3.09, acidic (b) 2.99 (c) 3.19 EXTRA 2C ANSWERS 1. (a) 20.0 ml (b) (c) 8.71 (d) 8.23 (e) 4.69 (f) 1.78 (g) (h) bromcresol green 2. (f) 1 x 10-2, 1 x 10-6 ) (g) bromphenol blue or methyl orange ( (h) o-cresolphthalein or phenolphthalein *3. (a) 20.0 ml (b) 3.65 (c) 6.12 (d) 6.60 (e) 7.08 (f) 9.71 (g) (h) 2.5 x 10-7 (i) thymolphthalein *4. 7 x *5. HCO 3 + H + H 2 O + CO 2 H + (from remaining HCl) + OH M H 2 O

8 EXTRA 2D ANSWERS x manganese (II) hydroxide 3. (a) 2 x M, 2 x 10-9 g/l (b) 5 x M, 5 x g/l 4. Yes *5. (a) 3.5 x 10-7 M (b) 6.3 x M *6. (a) 1.6 x 10-4 M (b) 4.4 x 10-6 M EXTRA 2E ANSWERS x M 2. 17% 3. (a) Ag + (b) 2.3 x M (c) M x M and 3.2 x 10 1 M *6. No precipitate will form *7. 9 x M, 9 x 10-8 M

9 EXTRA 2F ANSWERS 1. Isotope Stable or Radioactive Natural Abundance Half-Life Decay Mode 16 Ne Radioactive 9 x s 2p 17 Ne Radioactive ms β+ p 18 Ne Radioactive s β+ 19 Ne Radioactive s β+ 20 Ne Stable 90.48% 21 Ne Stable 0.27% 22 Ne Stable 9.25% 23 Ne Radioactive s β- 24 Ne Radioactive 3.38 m β- 25 Ne Radioactive 602 ms β- 26 Ne Radioactive 197 ms β-, β- n 27 Ne Radioactive 31.5 ms β-, β- n 28 Ne Radioactive 18.9 ms β-, β- n 29 Ne Radioactive 14.8 ms β-, β- n, β- 2n 30 Ne Radioactive 7.3 ms β-, β- n 31 Ne Radioactive 3.4 ms β- 32 Ne Radioactive 3.5 ms β- 33 Ne Radioactive < 180 ns n 34 Ne Radioactive > 60 ns β-, β- n 2. (a) 19 9F + 1 1H 16 8O + 4 2α (b) Lu Hf + 0-1β - (c) 11 6C 11 5B β + (d) 30 16S + 0-1e P (e) 26 12Mg + 1 0n 4 2α Ne (f) 16 8O + 2 1H 14 7N + 4 2α 3. (a) 70 32Ge 70 31Ga β + (b) 80 35Br 80 36Kr + 0-1β - (c) Fr 4 2α At (d) 26 14Si + 0-1e Al 4. (a) beta minus (b) beta plus or EC (c) alpha or spontaneous fission

10 EXTRA 2G ANSWERS days years minutes years old probably the result of French nuclear bomb testing in French Polynesia in the 1970 s, rendering radiocarbon dating in the area inaccurate x 10 9 years 6. (a) MeV/nucleon (b) MeV/nucleon * % 238 U and 22.68% 235 U * % 238 U and 0.32% 235 U

3. Determine the ph of a solution that is 0.75 M in hypochlorous acid and 0.35 M in sodium hypochlorite.

3. Determine the ph of a solution that is 0.75 M in hypochlorous acid and 0.35 M in sodium hypochlorite. HOMEWORK 2A 1. From the data given in Handout 3 on the class website, determine the pk a of the following acids. (a) Hydrocyanic acid (b) Hypochlorous acid (c) Formic acid 2. Determine if solutions of