Question

2 points 9. Using your textbook and class notes as a reference, indicate if cresol red would be a good acid-base indicator for this titration. Justify your answer using your knowledge of titrations curves and indicators. if we use cresol red which has a ph range of 8-10.5 it can good indicator because our titration is Naoh and ASA i.e strong base and weak acid so equivalence point is around ph=9. Cresol red can indicate this equivalence point by changing its colors from red to blue. 10. What would be the pH of 1L of a carbonate buffer of pH 7.57 if the ASA 3 points tablet used in this experiment has been added to it? (Assume the volume does not change, keep two digits after the decimal) 7.57 11. Why was ethanol first used to dissolve the ASA tablet? Justify your 2 points answer. Ethanol has a hydrophobic carbon chain. Water can be dissolved carboxylic acid

Answer 1

1 0.35 Cq Hg Oh + HO = Ca Hyon + Hiyo initial change (0.35-4) equilibrium [cation 7 Ho ka= (cq Hgoh] » 3.0x10 4 = 0:35-) x (x) (x) =x=0.0101m pH = -log(0.0101) →1.99. 2) Whale NHA THO NH4+40 = 1.0x10th ka = 10x10' 1.5 NH3 + H28 Kackb= initial change 1.8x405 (1.5-) equilibrium :5.55x100 (NA, [138] -10 5.55*10 ( x)(x) Enhet) » X5 2.88x105 M (15-) pH = -log(2.88x165) + 4.54 kar

= 7.28 2 3) pH = pkatlog ( salt pH = 7.20 +logGC48:5/141.96) 73414/119.98) Na H2PO4 = 119.95 9|mel 1.276 NaHpon = 111.969/mol 4) NaOH + Hel Nadla HO [Naoh] = MIVI Ooh x 80 +0.32M, [Hells (M+V2) ( 80+20) (VTV2) (80+20) concentration of Nauh left = 0.32-0.1 0.22 m pOH = -log(0.22) 0.657 +0.66. pH + pol sitt → PH = 16p -0.66 → 13.34 MV2 0.5X 20 OM