ALUATION (1O MINS) calculate the ratio of [CH3COOH/NACH3COO] to give a buffer solution at pH 5. Answer: 1.82 What is the pH of the solution of 35 mL 0.20 M formic acid and 55mL 0.10 M sodium formate in 110 mL water? pKa formic acid3D3.75 Answer:3.65 How many gram of ammonia should be added to 500mL of 1M ammonium chloride to give a pH 9? Ka ammonium%3D5.6x10-10 4.76 g ammonia Answer: 0.28 moles ammonia x 17g/mol ammonia =

ALUATION (1O MINS) calculate the ratio of [CH3COOH/NACH3COO] to give a buffer solution at pH 5. Answer: 1.82 What is the pH of the solution of 35 mL 0.20 M formic acid and 55mL 0.10 M sodium formate in 110 mL water? pKa formic acid3D3.75 Answer:3.65 How many gram of ammonia should be added to 500mL of 1M ammonium chloride to give a pH 9? Ka ammonium%3D5.6x10-10 4.76 g ammonia Answer: 0.28 moles ammonia x 17g/mol ammonia =

Chemistry: The Molecular Science

5th Edition

ISBN:9781285199047

Author:John W. Moore, Conrad L. Stanitski

Publisher:John W. Moore, Conrad L. Stanitski

Chapter15: Additional Aqueous Equilibria

Section: Chapter Questions

Problem 30QRT

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Similar questions

A friend asks the following: Consider a buffered solution made up of the weak acid HA and its salt NaA. If a strong base like NaOH is added, the HA reacts with the OH to form A. Thus the amount of acid (HA) is decreased, and the amount of base (A) is increased. Analogously, adding HCI to the buffered solution forms more of the acid (HA) by reacting with the base (A). Thus how can we claim that a buffered solution resists changes in the pH of the solution? How would you explain buffering to this friend?
A diprotic acid, H2B(MM=126g/moL), is determined to be a hydrate, H2B xH2O. A 10.00-g sample of this hydrate is dissolved in enough water to make 150.0 mL of solution. Twenty-five milliliters of this solution requires 48.5 mL of 0.425 M NaOH to reach the equivalence point. What is x?
Consider the following acids and bases: HCO2H Ka = 1.8 104 HOBr Ka = 2.0 109 (C2H5)2NH Kb = 1.3 103 HONH2 Kb = 1.1 108 Choose substances from the following list that would be the best choice to prepare a pH = 9.0 buffer solution. a. HCO2H b. HOBr c. KHCO2 d. HONH3NO3 e. (C2H5)2NH f. (C2H5)2NH2Cl g. HONH2 h. NaOBr
You have 0.10-mol samples of three acids identified simply as HX, HY, and HZ. For each acid, you make up 0.10 M solutions by adding sufficient water to each of the acid samples. When you measure the pH of these samples, you find that the pH of HX is greater than the pH of HY, which in turn is greater than the pH of HZ. a Which of the acids is the least ionized in its solution? b Which acid has the largest Kd?
What is an acidbase indicator? Define the equivalence (stoichiometric) point and the end point of a titration. Why should you choose an indicator so that the two points coincide? Do the pH values of the two points have to be within 0.01 pH unit of each other? Explain.
Water is accidentally added to 350.00 mL of a stock solution of 6.00 M HCI. A 75.00-mL sample of the diluted solution is titrated to pH 7.00 with 78.8 mL of 4.85 M NaOH. How much water was accidentally added? (Assume that volumes are additive.)
Metacresol purple is an indicator that changes from yellow to purple at pH 8.2. (a) What is Ka for this indicator? (b) What is its pH range? (c) What is the color of a solution with pH 9.0 and a few drops of metacresol purple?
Mixing together solutions of acetic acid and sodium hydroxide can make a buffered solution. Explain. How does the amount of each solution added change the effectiveness of the buffer?
A solution is made by dissolving 15.0 g sodium hydroxide in approximately 450 mL water. The solution becomes quite warm, but after it is allowed to return to room temperature, water is added to bring the volume to 500.0 mL of solution. (a) Calculate the pH and pOH in the final solution. (b) Why would we wait for it to return to room temperature? (c) If the mass of the water used to initially dissolve the sodium hydroxide were exactly 450 g and the temperature of the water increased by 8.865 C, how much heat was given off by the dissolution of 15.0 g of solute? Assume the specific heat of the solution is 4.184 J/g. K. What is the molar heat change for the dissolution of sodium hydroxide (known as the enthalpy of solution, Hsol)?
A solution has a pH of 4.5. What would be the color of the solution if each of the following indicators were added? (See Fig. 14-8.) a. methyl orange b. alizarin c. bromcresol green d. phenolphthalein