Chapter 17 Acids and Bases (same as Exam 2 Worksheet Answers)

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1 xam 3 Wrksheet Answers xam 3 Wrksheet Answers Chemistry 4 Chapter 17 Acids and Bases (same as xam Wrksheet Answers) 1. Fr the weak acids, what is the pk a and rank the acids accrding t strength? ; d e HNO > HCOOH > CH COOH > H CO > HCN > HCO Fr the weak bases, what is the pk b value and rank the bases accrding t strength? d e CH NH > CH N > NH > C H N > C H NH Fr the buffer slutins f 5 ml f.5 M HA and 35 ml f.0 M f the cnjugate salt, what is the ph? d What is the neutralizatin reactin fr each f the preceding buffers when cmbined with HCl? NH aq H aq NH aq 3 4 CN ( aq) H ( aq) HCN ( aq) F ( aq) H ( aq) HF ( aq) d. NO ( aq) H ( aq) HNO ( aq) 5. What is the ph f the slutin when ml f a M slutin f HCl is added? d

2 xam 3 Wrksheet Answers 6. What is the neutralizatin reactin fr each f the preceding buffers when cmbined with NaOH? NH aq OH aq NH aq H O l 4 3 HCN ( aq) OH ( aq) CN ( aq) HO( l) HF ( aq) OH ( aq) F ( aq) HO( l) d. HNO ( aq) OH ( aq) NO ( aq) H O( l) 7. What is the ph f the slutin when 5 ml f a 0.5 M slutin f NaOH is added? d Fr the titratin f 35.0 ml f a M nitric acid with M NaOH, what is the ph at each f these vlumes f NaOH added? d e. Many mst likely select phenlphthalein f ml g Fr the titratin f 35.0 ml f a M nitrus acid with M NaOH, what is the ph at each f these vlumes f NaOH added? d e. Many mst likely select phenlphthalein f ml g Fr the titratin f 35.0 ml f a M methyl amine with M hydrbrmic acid, what is the ph at each f these vlumes f HBr added? d..3 e. Many mst likely select methyl f ml g. 6.3

3 xam 3 Wrksheet Answers 11. What is the reactin fr a saturated slutin f all sulfides in Table 17. (p. 607)? 3 BiS3 s Bi aq 3S ( aq) CdS( s) Cd ( aq) S ( aq) CS( s) C ( aq) S ( aq) d. CuS( s) Cu ( aq) S ( aq) e. FeS( s) Fe ( aq) S ( aq) f. PbS( s) Pb ( aq) S ( aq) g. MnS( s) Mn ( aq) S ( aq) h. HgS( s) Hg ( aq) S ( aq) i. NiS( s) Ni ( aq) S ( aq) j. AgS s Ag aq S ( aq) k. SnS( s) Sn ( aq) S ( aq) l. ZnS( s) Zn ( aq) S ( aq) 1. What is the crrespnding values fr the reactins in number 11 and equilibrium expressin fr these values? Bi S = Cd S = C S = 4.0 d. 37 Cu S = 6.0 e. 19 Fe S = 6.0 f. 8 Pb S = 3.4 g. 14 Mn S = 3.0 h. 54 Hg S = 4.0 i. 4 Ni S = 1.4 j. 51 Ag S = 6.0 k. 6 Sn S = 1.0 l. 3 Zn S = What is the mlar slubility f each salt frm number 11? M.8 14 M M d M e. 7.7 M f M g M 3

4 xam 3 Wrksheet Answers h..0 7 M i M j M k M l M 14. What mass f the salt wuld be disslved in 1.5 L f water at 5 C? g g g d g e. 1.0 g f g g.. 5 g h g i. 1.6 g j g k g l. 8.0 g 15. What is the mlar cncentratin f each metal in in M sdium sulfide (frm number 11)? M M M d M e M f M g M h M i M j M k M l M 16. When equal vlumes f M sdium sulfide and M metal nitrates (frm number 11) are cmbined, what will happen? Because Q fr M is 5.6 9, Q > K s all MS salts will precipitate (where M = metal) Because Q fr Ag is 4. 13, Q > K s Ag S will precipitate Because Q fr Bi 3 is.4 1, Q > K s Bi S 3 will precipitate 4

5 xam 3 Wrksheet Answers 17. Fr a slutin 1.0 L f M tin nitrate, silver nitrate and bismuth nitrate, when adding cncentrated sdium sulfide (such that adding the sdium hydrxide will nt change the ttal vlume) answer: Which salt will precipitate first? Ag S Which salt will precipitate secnd? SnS Which salt will precipitate last? Bi S 3 d. What is the cncentratin f the first metal in that precipitated when the secnd salt begins t precipitate?.7 13 M e. What is the cncentratin f the secnd metal in that precipitated when the third salt begins t precipitate? M f. Can these salts be selectively precipitated? Ag S yes; Bi S 3 and SnS n Chapter 6 and Chapter 18 Thermdynamics 1. What is the standard change in enthalpy at 5 C fr the reactins? Assign whether the prcess is endthermic r exthermi kj; exthermic kj; endthermic 17.8 kj; exthermic d kj; exthermic. What is the standard change in enthalpy at 5 C fr the verall reactin given the thermchemical equatins? Assign whether the prcess is endthermic r exthermi 134 kj; exthermic 8 kj; exthermic 17.8 kj; exthermic d kj; exthermic e kj; exthermic 3. What is the standard enthalpy f frmatin at 5 C f the substances, given the thermchemical reactins? Assign whether the prcess is endthermic r exthermi 463 kj ml 1 ; exthermic 14.4 kj ml 1 ; endthermic kj ml 1 ; exthermic d. 188 kj ml 1 ; exthermic 4. What is the standard enthalpy f frmatin at 5 C f each substance given the change in enthalpy f reactin? Assign whether the prcess is endthermic r exthermi 77.6 kj ml 1 ; exthermic 57.5 kj ml 1 ; exthermic kj ml 1 ; exthermic d kj ml 1 ; exthermic 5

6 xam 3 Wrksheet Answers 5. What is the frmatin reactin fr each substance? 6C( s) 3H( g) 1 O( g) C6H5OH ( l ) Cs O g CO g Cs 1 O ( g) COg d. 8C( s) 9H( g) C8H18( l) e. N( g) 1 O( g) NO( g ) f. N ( g) H ( g) N H ( g) 4 6. Which substance will have a higher standard mlar entrpy? NH 3 (g) N H 4 (g) Fe(l) d. Br (l) e. Br (l) f. I (l) 7. Which prcesses are spntaneus? All are at 1 atm f pressure. Ice melting at 5 C Ice melting at 5 C Water freezing at 5 C d. Water freezing at 5 C e. Lithium hydrxide disslving in water (unsaturated slutin) f. Lithium hydrxide slidifying in water (unsaturated slutin) g. Sugar (C 1 H O 11 ) disslving in water (unsaturated slutin) h. Sugar (C 1 H O 11 ) slidifying in water (unsaturated slutin) i. A ht piece f irn in cntact with a cld piece f cpper and cpper getting htter and the irn getting clder. j. A ht piece f irn in cntact with a cld piece f cpper and irn getting htter and the cpper getting clder. 8. stimate the standard entrpy at 5 C f reactin in number 1. ΔS < 0 ΔS > 0 Cannt be estimated (Δn gas = 0) d. ΔS < 0 9. Determine the standard entrpy at 5 C f reactin in number J K J K J K 1 6

7 xam 3 Wrksheet Answers d J K 1 e kj; exthermic f kj; endthermic g kj; exthermic h kj; exthermic. stimate spntaneity f the reactins at 5 C in number 1. Spntaneus (ΔG < 0) Nt spntaneus (ΔG > 0) Spntaneus (ΔG < 0) d. Spntaneus (ΔG < 0) 11. Calculate the change in Gibbs free energy at 5 C fr the reactins in number kj kj 19.4 kj d kj 1. Will the reactins at 5 C in number 1 (a) be spntaneus (b) never be spntaneus (c) be spntaneus nly at high temperatures (d) be spntaneus nly at lw temperatures? If the reactin is spntaneus nly at certain temperatures [(c) r (d)], at what temperature des the spntaneity switch? Spntaneus at lw temperatures (39 K / 55 C) Spntaneus at high temperatures (18 K / 835 C) Spntaneus at all temperatures d. Spntaneus at lw temperature (000 K / 9730 C) 13. What are the equilibrium cnstants at 5 C fr the reactins in number 1? What des this mean in terms f cncentratin f reactants vs prducts? 8.9 [reactants] [prducts] [reactants] > [prducts] 4.8 [reactants] < [prducts] d. Very large [reactants] < [prducts] 14. Fr the reactin belw, is this reactin spntaneus at 5 C? The pressure f each reactant is 1.0 atm and the pressure the prduct is atm at 5 C, what is ΔG? Is the reactin spntaneus under these cnditins? NO( g) N( g) NO( g) The reactin is nt spntaneus under standard cnditins (ΔG = 33.8 kj) hwever under the nn standard cnditins, the reactin is spntaneus (ΔG = 9.83 kj). 7

8 xam 3 Wrksheet Answers 15. What is the biling pint f carbn disulfide assuming enthalpy and entrpy are cnstant with changing temperature? 33 K / 50 C 16. Is the uctin f cpper(ii) sulfide spntaneus? If nt, can cupling this reactin t the reactin f sulfur and xygen t sulfur dixide make the refinement f cpper becme spntaneus? Is this cupled reactin then spntaneus at all temperatures? CuS ( s) Cu( s) S ( s) Δ G = 49.0 kj nt spntaneus CuS ( s) O( g ) Cu( s) SO( g ) Δ G = 51.4 kj spntaneus ΔH = 47.6 kj ΔS =.3 J K 1 always spntaneus Chapter 19 lectrchemistry ( nly) 1. What is the xidatin state f each element? 0 0 d. 0 e. f. g. 0. What is the xidatin state f each element? Li: O: H: Fe: 3 O: S: 6 Al: 3 O: N: 5 d. C: 4 O: e. C: O: f. I: 7 Cl: g. Cd: O: P: 5 h. Mn: 4 O: 3. Balance the x reactins, identifying fr each which species is gaining r lsing electrns, and which is xidatin and which is uctin. Fe ( aq) e Fe( s) gaining electrns / uctin Ag ( s) Ag ( aq) e lsing electrns / xidatin Net inic: Fe ( aq) Ag ( s) Fe( s) Ag ( aq) Overall: Fe NO aq Ag s Fe s AgNO aq 3 3 8

9 xam 3 Wrksheet Answers d. Cl aq Cl g e lsing electrns / xidatin Zn aq e Zn s gaining electrns / uctin Net inic: Cl aq Zn aq Zn s Cl g Overall: NaCl aq Zn NO aq Zn s Cl g NaCl aq ( 3) ( 3) 3 Au aq 3e Au s gaining electrns / uctins Cu s Cu aq e lsing electrns / xidatin Net inic: Au aq 3Cu s 3Cu aq Au s Overall: Au NO aq 3Cu s 3Cu NO aq Au s F g e F aq gaining electrns / uctin H O aq O g 4e 4H aq lsing electrns / xidatin Net inic: F g H O aq 4HF aq O g Overall: F g H O aq 4HF aq O g 4. Balance the x reactins in acidic slutin, identifying each half reactin as xidatin r uctin. SO aq 4H aq e SO g H O l uctin 4 Fe s Fe aq e xidatin H SO aq Fe s SO g H O l FeSO aq 4 4 d. () 3 7 H O l O g 4H aq 4e uctin Cr O aq 14H aq 6e Cr aq 7H O l xidatin 3 7 Net inic: Cr O aq 16H aq 3O g 4Cr aq 8H O l Overall: H Cr O aq 1HNO aq 3O g 4Cr NO aq 8H O l PbO s SO aq 4H aq e PbSO s H O l uctin Pb s SO aq e PbSO s xidatin PbO s Pb s SO aq 4H aq PbSO s H O l SO g H O l SO aq 4H aq e xidatin I s e I aq uctin Net inic: SO g H O l I s I aq SO aq 4H aq Overall: SO g H O l I s HI aq H SO aq 4 9

10 xam 3 Wrksheet Answers e. f. g. h. 3 Br aq Br l e xidatin NO aq 4H aq 3e NO g H O l uctin 3 Net inic: 6Br aq NO aq 8H aq 3Br l NO g 4H O l Overall: 6HBr aq HNO aq 3Br l NO g 4H O l 3 MnO s 4H aq e Mn aq H O l uctin Cl aq Cl g e xidatin MnO s 4H aq Cl aq Mn aq Cl g H O l Overall : MnO s 4HCl aq MnCl aq Cl g H O l MnO s 4H aq e Mn aq H O l uctin Br aq Br l e xidatin MnO s 4H aq Br aq Mn aq Br l H O l Overall : MnO s 4HBr aq MnBr aq Br l H O l 3 3 Cu s Cu aq e xidatin NO aq 4H aq 3e NO g H O l uctin NO g 4H O l 3Cu aq 3Cu s NO aq 8H aq Overall: NO g 4H O l 3Cu NO aq 3Cu s 8HNO aq Balance the x reactins in basic slutin, identifying each half reactin as xidatin r uctin. H g OH aq H O l e xidatin e Cu aq Cu s uctin H g Cu aq OH aq H O l Cu s Ni s Ni aq e xidatin O g H O l 4e 4OH aq uctin O g H O l Ni s Ni OH s 4 () () MnO s 4OH aq MnO aq H O l 3e xidatin Br l e Br l uctin MnO s 8OH aq 6Br l MnO aq 4H O l 3Br l 4

11 xam 3 Wrksheet Answers 6. Fr the reactins yu balanced in number three answer: Fe aq e Fe s = 0.44 V cathde reactin; cathde = Fe s Ag ( s) Ag ( aq) e x = 0.80 V ande reactin; ande = Ag ( s) cell = 1.4 V Nt spntaneus (reverse reactin is spntaneus, s electrns wuld spntaneusly flw frm irn t silver) Ag(s) Ag (aq) (1 M) ǁ Fe (aq) (1 M) Fe(s) d. x = = = = Cl aq Cl g e 1.36 V ande reactin; ande Pt s Zn aq e Zn s 0.76 V cathde reactin; cathde Zn s cell =.1 V Nt spntaneus (reverse reactin is spntaneus, s electrns wuld spntaneusly flw frm zinc t platinum) Zn (aq) (1 M) Zn(s) ǁ Cl (aq) (1 M) Cl (g) Pt(s) 3 = = = = Au aq 3e Au s 1.50 V cathde reactin; cathde Au s Cu s Cu aq e x 0.34 V ande reactin; ande Cu s cell = 1.16 V electrns flw frm cpper t gld (ande t cathde) Spntaneus Au 3 (aq) (1 M) Au(s) ǁ Cu(s) Cu (aq) (1 M) = = = = F g e F aq.87 V cathde reactin; cathde Pt s H O aq O g 4e 4H aq 1.3 V ande reactin; ande Pt s x cell = 1.64 V Spntaneus electrns flw frm ande t cathde Pt(s) F (g) F (aq) (1 M) ǁ H O(l) O (g) Pt(s) 7. Fr the reactins yu balanced in number fur answer: SO4 ( aq) 4H ( aq) e SO( g) HO( l ) = 0.0 V cathde reactin; cathde = Pt s Fe s Fe aq e x = 0.44 V ande reactin; ande = Fe s cell = 0.4 V Nt spntaneus (reverse reactin is spntaneus, s electrns wuld spntaneusly flw frm platinum t irn) () H O l O g 4H aq 4e x 3 7 = 1.3 V ande reactin; ande = Pt s Cr O aq 14H aq 6e Cr aq 7H O l = 1.33 V cathde reactin; cathde = Pt s 11

12 xam 3 Wrksheet Answers cell = 0. V Spntaneus electrns flw frm ande t cathde d. e. f. PbO s SO aq 4H aq e PbSO s H O l 4 4 = = 1.70 V cathde reactin; cathde PbO s Pb s SO4 aq e PbSO4 s x = 0.31 V ande reactin; ande = Pb s cell =.01 V electrns flw frm lead t lead(iv) xide (ande t cathde) Spntaneus SO( g) HO( l) SO4 ( aq) 4H ( aq) e = 0.0 V ande reactin; ande = Pt s I s e I aq cell = 0.33 V Spntaneus Br aq Br l e x = 0.53 V cathde reactin; cathde = Pt s electrns flw frm ande t cathde x 3 = 1.07 V ande reactin; ande = Pt s NO aq 4H aq 3e NO g H O l = 0.96 V cathde reactin; cathde = Pt s cell = 0.11 V Nt spntaneus (reverse reactin is spntaneus, s electrns wuld spntaneusly flw frm platinum (Br uctin) t platinum (NO xidatin)) MnO s 4H aq e Mn aq H O l 1.3 V cathde reactin; cathde MnO s = = Cl aq Cl g e x = 1.36 V ande reactin; ande = Pt s cell = 0.13 V Nt spntaneus (reverse reactin is spntaneus, s electrns wuld spntaneusly flw frm MnO t platinum) 1

13 xam 3 Wrksheet Answers g. h. MnO s 4H aq e Mn aq H O l Br aq Br l e x = 1.3 V cathde reactin; cathde = MnO s = 1.07 V ande reactin; ande = Pt s cell = 0.16 V electrns flw frm platinum t MnO (ande t cathde) Spntaneus Cu s Cu aq e x NO aq 4H aq 3e NO g H O l 3 = 0.34 V ande reactin; ande = Cu s = 0.96 V cathde reactin; cathde = Pt s cell = 0.6 V electrns flw frm cpper t platinum (ande t cathde) Spntaneus 8. Fr the reactins yu balanced in number five answer: H g OH aq H O l e x e Cu aq Cu s = 0.83 V ande reactin; ande = Pt s = 0.34 V cathde reactin; cathde = Cu s cell = 1.17 V electrns flw frm platinum t cpper (ande t cathde) Spntaneus Ni s Ni aq e x O g H O l 4e 4OH aq = 0.5 V ande reactin; ande = Ni s = 0.40 V cathde reactin; cathde = Pt s cell = 0.65 V electrns flw frm nickel t platinum (ande t cathde) Spntaneus MnO s 4OH aq MnO aq H O l 3e 4 () () Br l e Br l x = 0.59 V ande reactin; ande = MnO s = 1.07 V cathde reactin; cathde = Pt s cell = 0.48 V electrns flw frm MnO t platinum (ande t cathde) Spntaneus 13

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( ) ( ) + ( ) ( ) ( ) + ( ) xam 4 Wrksheet Answers xam 4 Wrksheet Answers Chemistry 104 Chapter 19 lectrchemistry (19.1 19.3 repeated frm xam 3 wrksheet) 1. What is the xidatin state f each element? 0 0 d. 0 e. f. g. 0. What is the