A chemistry graduate student is given 250. mL of a 0.50M dimethylamine ((CH3)2NH) solution. Dimethylamine is a weak base with K, =5.4× 10-4What mass of (CH3)2NH2Cl should the student dissolve in the (CH3)2NH solution to turn it into a buffer with pH = 11.04?You may assume that the volume of the solution doesn't change when the (CH3)2NH2Cl is dissolved in it. Be sure your answer has a unit symbol, andround it to 2 significant digits.

Answered: A chemistry graduate student is given…

Chemistry: Principles and Reactions

8th Edition

ISBN:9781305079373

Author:William L. Masterton, Cecile N. Hurley

Publisher:William L. Masterton, Cecile N. Hurley

Chapter14: Equilibria In Acid-base Solutions

Section: Chapter Questions

Problem 26QAP: You want to make a buffer with a pH of 10.00 from NH4+/NH3. (a) What must the [ NH4+ ]/[ NH3 ]ratio...

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A buffer is made up of 239 mL of 0.187 M potassium hydrogen tartrate (KHC4H4O6) and 137 mL of 0.288 M potassium tartrate (K2C4H4O6). Ka for is (H2C4H4O6)4.55105. Assuming volumes are additive, calculate (a) the pH of the buffer. (b) the pH of the buffer after adding 0.0250 mol of HCI to 0.376 L of the buffer. (c) the pH of the buffer after adding 0.0250 mol of KOH to 0.376 L of the buffer.
Marble is almost pure CaCO3. Acid rain has a devastating effect on marble statuary left outdoors. Assume that the reaction which occurs is CoCO3(s)+ H+(aq)Ca2+(aq)+HCO3(aq) Neglecting all other competing equilibria and using Tables 15.1 and 13.2, calculate (a) K for the reaction. (b) the molar solubility of CaCO3 in pure water. (c) the molar solubility of CaCO3 in acid rainwater with a pH of 4.00.
Which of the following would form a buffer if added to 250.0 mL of 0.150 M SnF2? (a) 0.100 mol of HCl (b) 0.060 mol of HCI (c) 0.040 mol of HCl (d) 0.040 mol of NaOH (e) 0.040 mol of HF
A buffer solution with it pH of 12.00 consists of Na3PO4 and Na2HPO4. The volume of solution is 200.0 mL. (a) Which component of the buffer is present in a larger amount? (b) If the concentration of Na3PO4 is 0.400 M, what mass of Na2HPO4 is present? (c) Which component of the buffer must be added to change the pH to 12.25? What mass of that component is required?
When 40.00 mL of a weak monoprotic acid solution is titrated with 0.100-M NaOH, the equivalence point is reached when 35.00 mL base has been added. After 20.00 mL NaOH solution has been added, the titration mixture has a pH of 5.75. Calculate the ionization constant of the acid.
A buffer is prepared using the butyric acid/butyrate (HC4H7O2/C4H7O2)acid-base pair. The ratio of acid to base is 2.2 and Ka for butyric acid is1.54105. (a) What is the pH of this buffer? (b) Enough strong base is added to convert 15% of butyric acid to the butyrate ion. What is the pH of the resulting solution? (c) Strong acid is added to the buffer to increase its pH. What must the acid/base ratio be so that the pH increases by exactly one unit (e.g., from 2 to 3) from the answer in (a)?
What is the pH of a buffer that is 0.175 M in a weak acid and 0.200 M in the acids conjugate base? The acids ionization constant is 5.7 104.
Calculate the pH change when 10.0 mL of 0.100-M NaOH is added to 90.0 mL pure water, and compare the pH change with that when the same amount of NaOH solution is added to 90.0 mL of a buffer consisting of 1.00-M NH3 and 1.00-M NH4Cl. Assume that the volumes are additive. Kb of NH3 = 1.8 × 10-5.
A good buffer generally contains relatively equal concentrations of weak acid and conjugate base. If you wanted to buffer a solution at pH = 4.00 or pH = 10.00, how would you decide which weak acidconjugate base or weak baseconjugate acid pair to use? The second characteristic of a good buffer is good buffering capacity. What is the capacity of a buffer? How do the following buffers differ in capacity? How do they differ in pH? 0.01 M acetic acid/0.01 M sodium acetate 0.1 M acetic acid/0.1 M sodium acetate 1.0 M acetic acid/1.0 M sodium acetate
Ammonia gas is bubbled into 275 mL of water to make an aqueous solution of ammonia. To prepare a buffer with a pH of 9.56, 15.0 g of NH4Cl are added. How many liters of NH3; at 25C and 0.981 atm should be used to prepare the buffer? Assume no volume changes and ignore the vapor pressure of water.
A 1.0-L solution that is 4.2 M in ammonia is mixed with 26.7 g of ammonium chloride. a What is the hydroxide-ion concentration of this solution? b 0.075 mol of MgCl2 is added to the above solution. Assume that there is no volume change. After Mg(OH)2 has precipitated, what is the molar concentration of magnesium ion? What percent of the Mg2+ is removed from solution?
Ka for formic acid is 1.7 104 at 25C. A buffer is made by mixing 529 mL of 0.465 M formic acid, HCHO2, and 494 mL of 0.524 M sodium formate, NaCHO2. Calculate the pH of this solution at 25C after 110 mL of 0.152 M HCl has been added to this buffer.

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