4. Select/choose an appropriate chemical indicator for the following titration set-up and explain why you chose that indicator: a. weak acid + strong base if pH at equivalence pt = 9 b. Weak base + strong acid if pH at equivalence pt = 5 c. Strong acid + strong base if pH at equivalence pt = 7 Indicator Acid Alkaline Approximate pKa(In) pH range (HIn) (In") Methyl Violet Thymol Blue Methyl Orange Bromophenol Blue Methyl Red Bromocresol Purple Bromothymol Blue yellow blue 0.0 - 1.6 red yellow yellow 1.2 - 2.8 1.7 red 3.1 - 4.4 3.4 yellow red blue 2.9 - 4.6 4.0 yellow purple blue 4.2 - 6.3 5.1 yellow yellow yellow yellow colourless 5.2 - 6.8 6.0 - 7.6 6.8 - 8.4 6.3 7.0 Phenol Red red 7.9 Thymol Blue Phenolphthalein blue 8.0 - 9.6 8.9 red 8.3 - 10.0 9.4 A

4. Select/choose an appropriate chemical indicator for the following titration set-up and explain why you chose that indicator: a. weak acid + strong base if pH at equivalence pt = 9 b. Weak base + strong acid if pH at equivalence pt = 5 c. Strong acid + strong base if pH at equivalence pt = 7 Indicator Acid Alkaline Approximate pKa(In) pH range (HIn) (In") Methyl Violet Thymol Blue Methyl Orange Bromophenol Blue Methyl Red Bromocresol Purple Bromothymol Blue yellow blue 0.0 - 1.6 red yellow yellow 1.2 - 2.8 1.7 red 3.1 - 4.4 3.4 yellow red blue 2.9 - 4.6 4.0 yellow purple blue 4.2 - 6.3 5.1 yellow yellow yellow yellow colourless 5.2 - 6.8 6.0 - 7.6 6.8 - 8.4 6.3 7.0 Phenol Red red 7.9 Thymol Blue Phenolphthalein blue 8.0 - 9.6 8.9 red 8.3 - 10.0 9.4 A

Chemistry

10th Edition

ISBN:9781305957404

Author:Steven S. Zumdahl, Susan A. Zumdahl, Donald J. DeCoste

Publisher:Steven S. Zumdahl, Susan A. Zumdahl, Donald J. DeCoste

Chapter1: Chemical Foundations

Section: Chapter Questions

Problem 1RQ: Define and explain the differences between the following terms. a. law and theory b. theory and...

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+ Base/Acid Ratios in Buffers Just as pH is the negative logarithm of [H3O+]. PK₂ is the negative logarithm of Ka. PK₂ -log Ka The Henderson-Hasselbalch equation is used buffer solutions: calculate the pH of base DAGSK pH =pK₂ +log acid] Notice that the pH of a buffer has a value close to the PK₂ of the acid. differing only by the logarithm of the concentration ratio [base]/[acid]. The Henderson-Hasselbalch equation in terms of pOH and PKb is similar. acid [base pOH = pkt + log- Part A Acetic acid has a K₁ of 1.8 x 105. Three acetic acid/acetate buffer solutions, A, B, and C, were made using varying concentrations: A. [acetic acid] ten times greater than [acetate]. B. [acetate] ten times greater than [acetic acid], and c. [acetate] [acetic acid]. Match each buffer to the expected pH Drag the appropriate items to their respective bins. ▸ View Available Hint(s) [acetic acid] ten times greater than [acetate] pH = 3.74 [acetate] ten times greater than [acetic acid] pH = 4.74 Reset Help…
7. Refer to the following table: Table 2-2. Change in pH of 0.2 M Acetate Buffer after addition of Acid or Base [Base]:[Acid] 0.005:0.195 Addition pH HC1 0.095 mol 3.1 HC1 0.075 0.025:0.175 3.9 HС1 0.05 НС1 0.025 0.05:0.15 4.2 0.075:0.125 4.5 0.1:0.1 0.125:0.075 4.7 NaOH 0.025 mol 4.9 NaOH 0.05 mol 0.15:0.05 5.2 NaOH 0.75 mol 0.175:0.025 5.5 NaOH 0.095 mol 0.195:0.005 6.3 a. Calculate the pH of a 0.2 M acetate buffer (a solution containing 0.1 mol L-' acetic acid and 0.1 mol L-1 sodium acetate), given that the pKa of acetic acid is 4.7. b. What would be the pH value after adding 0.05 mol of NaOH to 1 L of 0.2 mol L1 acetate buffer? c. Compare the pH value in (b) with that obtained after adding 0.05 mol NAOH to 1 L of water (a simple solution of 0.05 mol L-' NaOH). d. How much acid or base can be added to 1 L of the 0.2 M acetate buffer so that the pH does not change appreciably (i.e., what is its buffer range)?
7- In acid-base titration, the Phenolphthalein indicator will change its colour from what to what? * colourless to pink colourless to red yellow to colourless No colour change
titration curve in acid-base titration is: a. less steep curve for strong analyte versus strong titrant than weak ones b. all acid-base indicator are suitable for use c. the end point does not necessary match pH=7 for all types of acid and base analytes d. weak acid can be used for titrating weak bases
Match with the best answer. bronsted acid bronsted base H2S H2O/OH- molar solubility neutral acid-base indicator H3PO4 ✓[Choose ] proton donor compound that changes color with pH and is used in titrations acid/base conjugate pair diprotic acid pH=pOH solubility of a solid compound in moles/liter proton acceptor triprotic acid [Choose] [Choose ] [Choose ] [Choose ] [Choose ]
What is the pH of a buffer system that is 0.25 M in NH3 and 0.26 M in NHẠC?? Кь NH3 %3D 1.8 х 10:5 NOTE: Even though this system involves the weak base NH3 and its conjugate acid NH4*, it is still possible to use the Henderson-Hasselbalch equation using pKą for the weak acid NH4* and the ratio of [conjugate base]/[conjugate acid]. You do not need to convert the equation and use a pКь value.
Determine the resulting pH when 0.0015 mol of solid Ba(OH)2 is added to a 0.350 L buffer containing 0.110 M weak acid, HA, and 0.220 M of its conjugate base, A-. The value of Ka for HA is 3.2 x 10-9. PREV 1 2 3 4 NEXT Based on your ICE table and definition of Ka, set up the expression for Ka in order to determine the unknown. Do not combine or simplify terms. Ка = 3.2 x 10-9 %3D 5 RESET [0] [0.110] [0.220] [0.101] [0.229] [0.106] [x] [2x] [0.110 + x] [0.110 - x] [0.220 + x] [0.220 - x] [0.101 + x] [0.101 - x] [0.229 + x] [0.229 - x] [0.106 + x] [0.106 - x]
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12. A 1.00 L buffer solution is 0.150 M in weak organic acid HC₂H5O₂ and 0.250 M in LiC7H5O2. Calculate the pH of the solution after the addition of 0.01 mol HCI. The Ka for HC₂H5O2 is 6.5 x 10-5. (hint: the total volume after adding 100ml of HCl solution turn to 1.00L+100ml = 1.10 L, so molarity calculation should be based off the new volume)
se or conjugate base. 12 2. A 50.0mL sample of an acid HA, of unknown molarity is titrated with 0.1000 M KOH. The pH of the resulting solution is measure with a pH meter and graphed below. Select the letter that corresponds to the following. Some letters may be used more than once. Some may not be used at all. 10+ a. the equivalence point: R 9 b. the half equivalence point: Q 8+ c. where [KOH] is greatest: 7+ P I of d. where [H+] is greatest: T e. where [HA]=[A-]: 5+ 4 f. where [A-] is the predominate species: 3+ 2 SO a. What is pH after 10.0mL of 0.15M NaOH solution has been added to 25.0 mL of 0.12M HF solution? Ka = 6.8 x 10-4. b. After adding NaOH, is the resulting solution a buffer solution? Explain. 3. Complete the following calculations. (P) (Q) 84 3 ST PR
Please answer; they were all the same choices.
Calculate the pH during the titration with NaOH after addition of: a) 50.00 mL of 0.1000 mol L-1 NaOH to 50.00 mL of 0.1000 mol L-1 CH3COOH (Ka= 1.75 x 10-5). b) Based on the table below, which indicator (A, B or C) is most appropriate to monitor this titration? Explain. Indicator A B C pKIndicator 3.8 9.3 5.0 Actual Transition Range (pH) 3.0 to 4.6 3.0 to 4.6 4.4 to 6.2