( x) [ ] ( ) ( ) ( ) ( )( ) ACID-BASE EQUILIBRIUM PROBLEMS. Because HCO / K = 2.8 < 100 the xin the denominator is not going to be negligible.

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Claude Maxwell
5 years ago
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1 ACID-BASE EQUILIBRIUM PROBLEMS 1. Clculte the ph of solutio tht cotis M olic cid. Clculte the cocetrtio of the olte io i this solutio. 1 H C O 4 + H O Ý H 3O + + HC O HC O + H O Ý H 3O + + C O H C O 4 H 3O + HC O I E [ ] Becuse HCO /.8 < 0 the i the deomitor is ot goig to e egligile. 4 1 [ ] 4 ( 1.0 ) ( ) + H 3O HCO 4 + HCO ( 0.059) ( 0.059) 4( 1)( ) ± 4c ± , H3O HCO M HC O H 3O + C O I E ( ) + HO 3 CO HC O CO + H3O HCO M + ph log H3O log ( 0.035) 1.134

2 . Clculte the ph of 0.05 M solutio of diethylmie. (C H 5) NH + H O Ý (C H 5) NH + OH (C H 5) NH OH (C H 5) NH I E Becuse CH5 NH / the i the deomitor is ot goig to e egligile. < ( C H ) ( 6.9 ) ( 1.0 ) + OH C H5 NH NH ± 4c C H NH M 3 ( ) 4( 1)( ) ± 1 poh log OH log ph poh , ml of 0.4 M hydrochloric cid is dded to ml of M ethylmie solutio. Wht is the pproimte ph of the resultig solutio? Becuse hydrochloric cid is strog cid, we do the eutrliztio (limitig rectt) prt of the prolem first. H 3O + + C H 5NH C H 5NHœ + H O 14.4 mmol 14.8 mmol mmol mmol mmol mmol 14.4 mmol This leves us with uffer (sort of, the rtio is it outside of the 1: we prefer). The is so p is 3.19 ph [ C H NH ] 0.4 mmol p + C 14.4 mmol H5NH log log 9.5

3 4. Out of the followig, which is the est cid/se to use to prepre uffer with ph of 11.00?. hydroge peroide p pheol p 9.89 c. propylmie p.53 Wht rtio of msses of the wek cid/se d its cojugte should you use to mke the uffer of the required ph? Use the sodium slt of the cojugte se if you chose wek cid or the chloride slt of the cojugte cid if you chose wek se. I this prolem it s toss-up etwee usig hydroge peroide of propylmie. Both hve p out 0.5 ph uits from the ph we wt. The clcultios for oth re essetilly the sme. I m showig the clcultio for hydroge peroide here. HO ph p + log [ HO] [ HO] H O + H O Ý HO + H 3O + p 11.6 [ HO] log HO ph p HO HO HO mho M HO HO M HO HO mnho M g mol NHO NHO M NHO NHO So the mss rtio should e out.53 : g mol

4 5. Clculte the ph t the equivlece poit whe 5.00 ml of 0.16 M cyic cid is titrted with 0.08 M strotium hydroide solutio. Becuse strotium hydroide is strog se, we do the eutrliztio (limitig rectt) prt of the prolem first. OH + HCN CN + H O We clculte the volume of Sr(OH) solutio we eed to get to the equivlece poit. OH 0.16 mol HCN 1 mol OH 1 mol Sr OH 00 ml Sr OH sol' HCN 5.00 ml 00 ml HCN sol' 1 mol HCN mol OH 0.08 mol Sr OH 4.39 ml Sr OH sol' eeded. So the cocetrtio of the cojugte se s the equivlece poit is: 0.16 mol CN ( 5.00 ml)( 00 ml ) 3 L ml 1 ml M At the equivlece poit the oly thig left i the solutio is the cojugte se of the wek cid, CN. CN + H O Ý HCN + OH w/.0 5 CN HCN OH I E [ HCN ] OH ( ) 5.0 CN is less th 5% of so it is egligile here. 3 poh log log ( 1.3 ).90 ph poh 11.

5 6. Wht is the ph of solutio otied y ddig 0.0 g of sodium ezote to eough wter to mke 1. L of solutio? The ezote io is the cojugte se of ezoic cid. We eed to fid the cocetrtio of the ezote io d the. 0.0 g NCH6O 1 mol NCH6O 1 mol CH6O CHO M 1. L g NC H O 1 mol NC H O C H O (q) + H O(l) HC H O (q) + OH (q) w C H 6O HC H 6O OH I E ( 1.0 ) C H6O OH HCH6O ( ) OH poh log log ph poh 9.00

6 ml of 0.1 M lctic cid is titrted with 0.0 M sodium hydroide. Whe ml of the se hve ee dded wht should the pproimte ph e? Sodium hydroide is strog se so we eed to do the eutrliztio first: 0.0 mol OH mmol OH dded ml.1 mmol OH 1 L sol' 0.1 mol HC H O mmol HC H O dded 5.00 ml 4.5 mmol HC H O 1 L sol' OH + HC 3H 5O 3 H O + C 3H 5O The mouts of the wek cid d its cojugte se re o-zero here so we hve uffer. We c use the Hederso-Hsslelch equtio. ph.1 p CHO log 4.19 log 4.44 HC3H5O3 8. If p w t 5.0 C is 1.696, wht is the ph of pure wter t this temperture? I pure wter [H 3O + ] [OH ] so the ph poh. ph + poh pw if ph, the pw ph + poh ph + ph + pw 6.485

7 9. The ph of 0.18 M solutio of wek se is 1.6. Wht is the of the cojugte cid of the se? B + H O Ý HB + + OH B HB + OH I E poh ph poh 1.33 OH [ B] [ B] ( 4.68 ) + HB OH w HB 13. Etholmmmoium io hs p of Wht is the ph of 0.5 M solutio of etholmie? (C H 5OH)NH + H O Ý (C H 5OH)NHœ + OH (C H 5OH)NH (C H 5OH)NHœ OH I E ( ) ( ) 5 ( 1.0 ) + p 5 3 p C H OH NH OH CH5OH NH this vlue is out 1.% of 0.5 so the pproimtio is vlid 3 poh log log..5 ph p poh w.

Chapter 17: Additional Aspects of Aqueous Equilibria

Chapter 17: Additional Aspects of Aqueous Equilibria 1 Chpter 17: Additionl Aspects of Aqueous Equilibri Khoot! 1. Adding Br to sturted queous solution of decreses its solubility in wter. BSO 4, Li CO 3, PbS, AgBr. Which of the following mitures could be