Question

Assume you dissolve 0.132 g of the weak acid benzoic acid, C6H; CO2H, in enough water to make 1.00 x 102 mL of solution and then titrate the solution with 0.184 M NaOH.( K, for benzoic acid = 6.3 x 10-5.) CoH; CO, H(aq) + OH (aq) = C, H; CO2 (aq) + H20(4) a. What wasythe pH of the original benzoic acid solution? pH = b. What are the concentrations of all of the following ions at the equivalence point: Na H30+ OH, and C6H5 CO2 - ? [Na+]= H30+)-1 [OH-] = (C6H; CO2-) = c. What is the pH of the solution at the equivalence point? pH =

Answer 1

Answer: Giren 0-132 at ueak ben20ic acid drssolved in 0D mL af wTuter to make solutTon Affirst we have to catulote ine molarity of tne Solutim Molar mass ot benzoil acid = 122.12 amol'' 6H5 COOH 6X12+5x1.0 + 12+ 2X15 99+ a mo = 12212 Molavity Ms the concentrahien af a solutfan expr males gf solutc. per lat of expressed as : Solutim no mol no af moles Lit or solutfm Motarity mol bz acid 1000 m L O1329 benz0ic acid 122 12 benzoic acid 1L 00 mL 00108 mol LL 0.011 M Concentration at benzoic acid soluttn -0.011 (M Ka H5 COOH H C6 H5 COO ofc(M) (1-4JC (9 dearee t dissoualton с - ka Me degree otdissoc totion 区くく So, Ka

-2108Ka-8 PH pka Lacid NGw ben20ic acid = 6 3 x10 Ka PKa log (63A10 5- 4.2 10Ka [acid 0.01 M . pH of te riginal benz0ic acid soluton = 5.18 PH 10 (0 01 4.2 PH-5.18 bAt equivalante paint S1 Strength of Vz Uolume af Nao14 S01 S2Strength o NaoH Sot 0-184 M Nav, U2 50x0.01 5.97 mL O-189 5-97ML At equialance point, volume of NaoH

After addina 5.97 mL ot NatH Soluttan, ben2ai actd isa completey neutrallised Now Total oume of the solutin (100+ 5-91 - IG5.97 mL Amount of Na* 5.97x o- 184 milimole 09 mihmole . Canc at Na] -0.0102 M OD X 105 97 Na OH 00102 (M) Amount afg H5 Co0 Canc of H5 ( 00 -0 0103 M 05.97 00103 (M

At equiralance point, both the concentruton Tacid and base are equal andd they neuhralized each other C6H5 COOH NaoH C6 45 COD Na + H20 : t equiralance point ure get the pH value for the hydroysis of sot 6t5 CodNa Favm ula of pH at equi valance point giren by log salt 2 2 t On additim at 5.97 mL of Naolt souhin benzo acid is completei neutraused and the resulting praduck bein C6 t5 CODNa amount ofGH5COONa formed 5-97 x 0 189) 1.0g milimole - (I00 5.97 total volume ot solutim 105.97 mL : :[sout 0.0102 M IG00X 105.97 PHX X4-2 0102 7+ 2.10.96 813 PH at equiralance point =8.13