2. Given the H3PO4 - NaH₂PO4 buffer system, which of the following is false when KOH is added into the said solution? O The concentration of the H3PO4 will decrease upon addition of KOH. O The concentration of the H₂PO4 will decrease upon addition of KOH. O The concentration of the H₂PO4 will increase upon addition of KOH. O The [H₂PO4]/[H3PO4] will decrease due to the neutralization of the added KOH.

2. Given the H3PO4 - NaH₂PO4 buffer system, which of the following is false when KOH is added into the said solution? O The concentration of the H3PO4 will decrease upon addition of KOH. O The concentration of the H₂PO4 will decrease upon addition of KOH. O The concentration of the H₂PO4 will increase upon addition of KOH. O The [H₂PO4]/[H3PO4] will decrease due to the neutralization of the added KOH.

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

Chapter15: Acid-base Equilibria

Section: Chapter Questions

Problem 46E: An aqueous solution contains dissolved C6H5NH3Cl and C6H5NH2. The concentration of C6H5NH2 is 0.50 M...

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Enough water is added to the buffer in Question 29 to make the total volume 10.0 L. Calculate (a) the pH of the buffer. (b) the pH of the buffer after the addition of 0.0500 mol of HCl to 0.600 L of diluted buffer. (c) the pH of the buffer after the addition of 0.0500 mol of NaOH to 0.600 L of diluted buffer. (d) Compare your answers to Question 29(a)-(c) with your answers to (a)-(c) in this problem. (e) Comment on the effect of dilution on the pH of a buffer and on its buffer capacity.
Indicate whether each of the following statements is true or false. If the statement is false, restate it to make it true. (a) The formate ion (CHO2-) concentration in 0.10 M HCHO2 is the same as in 0.10 M NaCHO2. (b) A buffer can be destroyed by adding too much strong acid. (c) A buffer can be made up by any combination of weak acid and weak base. (d) Because Ka for HCO3- is4.71011, Kb for HCO3- is2.1104.
A buffer is composed of formic acid and its conjugate base, the formate ion. (a) What is the pH of a solution that has a formic acid concentration of 0.050 M and a sodium formate concentration of 0.035 M? (b) What must the ratio of acid to conjugate base be to have a pH value 0.50 units higher than the value calculated in part (a)?
Cacodylic acid, (CH3)2AsO2H, is a toxic compound that is a weak acid with pKa = 6.19. It is used to prepare buffered solutions. Calculate the masses of cacodylic acid and sodium cacodylate that should be used to prepare 500.0 mL of a pH = 6.60 buffer so that the buffer has a total of arsenic-containing species equal to 0.25 M, that is, so that: [(CH3)2AsO2H] + [(CH3)2AsO2] = 0.25 M
If added to 1 L of 0.20-M acetic acid, CH3COOH, which of these would form a buffer? 0.10 mol NaCH3COO 0.10 mol NaOH 0.10 mol HCl 0.30 mol NaOH Explain your answers.
Calculate the pH of a solution that is 0.40 M H2NNH2 and 0.80 M H2NNH3NO3. In order for this buffer to have pH = pKa, would you add HCl or NaOH? What quantity (moles) of which reagent would you add to 1.0 L of the original buffer so that the resulting solution has pH = pKa?
A best buffer has about equal quantities of weak acid and conjugate base present as well as having a large concentration of each species present. Explain.
Methyl orange, HMO, is a common acid-base indicator. In solution it ionizes according to the equation: HMOaqH+aq+MO-aqredyellow If methyl orange is added to distilled water, the solution turns yellow. If 1 drop or two of 6 M HCl is added to the yellow solution, it turns red. If to that solution one adds a few drops of 6 M NaOH, the color reverts to yellow. a. Why does adding 6 M HCl to the yellow solution of methyl orange tend to cause the color to change to red? Note that in solution HCl exists as H+ and Cl- ions. b. Why does adding 6 M NaOH to the red solution tend to make it turn back to yellow? Note that in solution NaOH exists as Na+ and OH- ions. How does increasing OH- shift Reaction 3 in the discussion section? How would the resulting change in H+ affect the dissociation reaction of HMO?
An aqueous solution contains dissolved C6H5NH3Cl and C6H5NH2. The concentration of C6H5NH2 is 0.50 M and pH is 4.20. a. Calculate the concentration of C6H5NH3+ in this buffer solution. b. Calculate the pH after 4.0 g NaOH(s) is added to 1.0 L of this solution. (Neglect any volume change.)
A sodium hydrogen carbonate-sodium carbonate buffer is to be prepared with a pH of 9.40. (a) What must the [ HCO3 ]/[ CO32 ]ratio be? (b) How many moles of sodium hydrogen carbonate must be added to a liter of 0.225 M Na2CO3 to give this pH? (c) How many grams of sodium carbonate must be added to 475 mL of 0.336 M NaHCO3 to give this pH? (Assume no volume change.) (d) What volume of 0.200 M NaHCO3 must be added to 735 mL of a 0.139 M solution of Na2CO3 to give this pH? (Assume that volumes are additive.)
Given the H3PO4 – NaH2PO4 buffer system, which of the following is false when KOH is added into the said solution? A. The concentration of the H3PO4 will decrease upon addition of KOH. B. The concentration of the H2PO4- will decrease upon addition of KOH. C. The concentration of the H2PO4- will increase upon addition of KOH. D. The [H2PO4-]/[H3PO4] will decrease due to the neutralization of the added KOH.
Given the HCOOH-KHCOO buffer system, which of the following is false when HBr is added into the said solution? A. The concentration of the HCOO will decrease upon addition of HBr. B. The concentration of the HCOOH will increase upon addition of HBr. C. The concentration of the HCOO will increase upon addition of HBr. D. The [HCOO ]/[HCOOH] will decrease due to the neutralization of the added HBr.