ACTIVITY 4 SOLOVING TIME! NUMBERS ONLY 1 & 2 logarithm of a ratio which can be solved by performing the antilogarithm of pH/pKa:10pH-pKa [base]An example of how to use the Henderson-Hasselbalch equation to solve for the pH of a buffer solution is as follows:1.What is the pH of a buffer solution consisting of 0.0350 M NH3 and 0.0500 M NH4+ (Ka for NH4+ is 5.6 x 10-10)?The equation for the reaction is:NH+ H+ + NH3Assuming that the change in concentrations is negligible, in order for the system to reach equilibrium, the Henderson-Hasselbalch equation will be:|NH:%3D['HN0.03501301+vd = HdpH = 9.25 +log ('0.0500%3DpH = 9.095Activity3. True or False!Directions: Write T if the statement is correct and F if otherwise. Write your answer before the number.1. If the buffer is made with a base and its conjugate acid, the pH can be adjusted using a weak acid like HCl.2. A buffer's pH changes greatly when a small amount of strong acid or base is added to it.3. A good buffer mixture should have about equal concentrations of both of its components.4. The strength of a weak acid (buffer) is usually represented as an equilibrium constant.5.The Henderson-Hasselbalch equation connects the measurable value of the pH of a solution with the theoreticalvalue pKa.Activity 4. It's Solving Time!Directions: Solve the following problem. Write your complete solutions.1. What is [H3O'] in a solution of 0.25 M CH3CO2H and 0.030 M NACH3CO2?CH3CO2H(aq)+H2Om=H30°(aq)+CH3CO2 (ag)2. What is [OH] in a solution of 0.125 M CH3NH, and 0.130 M CH3NH3CI?CH3NH2(aq)+H2Ou=CH3NH3 (aq)+OH (aq)K=1.8x105(be)Kp=4.4x10(be)Processing questions:1. Why is understanding of the concept of pH important?2. Why are buffer solutions relevant to life?Page | 5

Answered: Image /qna-images/answer/452fb176-9ea1-4902-94d5-96e537bd1232.jpg

Activity 4. It's Solving Time! Directions: Solve the following problem. Write your complete solutions. 1. What is [H3O'] in a solution of 0.25 M CH3CO2H and 0.030 M NACH3CO2? CH;CO,H(aq)+H2Oy=H30°(aq)+CH3CO2 (ag) 2. What is [OH] in a solution of 0.125 M CH3NH2 and 0.130 M CH3NH3CI? CH3NH2(aq)+H2O{u=CH3NH3 (aq)+OH (aq) K=1.8x103 K=4.4x10

Activity 4. It's Solving Time! Directions: Solve the following problem. Write your complete solutions. 1. What is [H3O'] in a solution of 0.25 M CH3CO2H and 0.030 M NACH3CO2? CH;CO,H(aq)+H2Oy=H30°(aq)+CH3CO2 (ag) 2. What is [OH] in a solution of 0.125 M CH3NH2 and 0.130 M CH3NH3CI? CH3NH2(aq)+H2O{u=CH3NH3 (aq)+OH (aq) K=1.8x103 K=4.4x10

Principles of Modern Chemistry

8th Edition

ISBN:9781305079113

Author:David W. Oxtoby, H. Pat Gillis, Laurie J. Butler

Publisher:David W. Oxtoby, H. Pat Gillis, Laurie J. Butler

Chapter15: Acid–base Equilibria

Section: Chapter Questions

Problem 107AP

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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.
Calculate the pH after mixing 15 mL of 0.12 M acetic acid with 15 ml of 0.12 M NaOH. What are the major species in solution at equilibrium (besides water), and what are their concentrations?
Sketch a titration curve for the titration of potassium hydroxide with HCl, both 0.100 M. Identify three regions in which a particular chemical species or system dominates the acid-base equilibria.
Each symbol in the box below represents a mole of a component in one liter of a buffer solution; represents the anion (X-), = the weak acid (HX), = H+, and =OH. Water molecules and the few H+ and OH- ions from the dissociation of HX and X- are not shown. The box contains 10 mol of a weak acid, , in a liter of solution. Show what happens upon (a) the addition of 2 mol of OH- (2 ). (b) the addition of 5 mol of OH- (5 ). (c) the addition of 10 mol of OH- (10 ). (d) the addition of 12 mol of OH- (12 ). Which addition (a)-(d) represents neutralization halfway to the equivalence point?
Enough water is added to the buffer in Question 30 to make the total volume 5.00 L. (a) Calculate the pH of the buffer. (b) Calculate the pH of the buffer after adding 0.0250 mol of HCl to 0.376 L of the buffer. (c) Calculate the pH of the buffer after adding 0.0250 mol of KOH to 0.376 L of the buffer. (d) Compare your answers to Question 30 (a-c) with your answers to (a-c) of this problem. (e) Comment on the effect of dilution on the pH of a buffer and on its buffer capacity. Â
Consider a solution formed by mixing 100.0 mL of 0.10 M HA (Ka = 1.0 106), 100.00 mL of 0.10 M NaA. and 100.0 mL of 0.10 M HCl. In calculating the pH for the final solution, you would make some assumptions about the order in which various reactions occur to simplify the calculations. State these assumptions. Does it matter whether the reactions actually occur in the assumed order? Explain.
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.)
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.
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?