A chemist must prepare 800.0 mL of potassium hydroxide solution with a pH of 12.80 at 25 °C. She will do this in three steps: • Fill a 800.0 mL volumetric flask about halfway with distilled water. • Weigh out a small amount of solid potassium hydroxide and add it to the flask. Fill the flask to the mark with distilled water. Calculate the mass of potassium hydroxide that the chemist must weigh out in the second step. Round your answer to 2 significant digits. ☐ g ☐ x10

A chemist must prepare 800.0 mL of potassium hydroxide solution with a pH of 12.80 at 25 °C. She will do this in three steps: • Fill a 800.0 mL volumetric flask about halfway with distilled water. • Weigh out a small amount of solid potassium hydroxide and add it to the flask. Fill the flask to the mark with distilled water. Calculate the mass of potassium hydroxide that the chemist must weigh out in the second step. Round your answer to 2 significant digits. ☐ g ☐ x10

Chemistry: Principles and Practice

3rd Edition

ISBN:9780534420123

Author:Daniel L. Reger, Scott R. Goode, David W. Ball, Edward Mercer

Publisher:Daniel L. Reger, Scott R. Goode, David W. Ball, Edward Mercer

Chapter16: Reactions Between Acids And Bases

Section: Chapter Questions

Problem 16.80QE: Calculate the pH of each of the following solutions. (a) 10.0 mL of 0.300 M hydrofluoric acid plus...

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Strong Acids, Weak Acids, and pH Two 0.10-mol samples of the hypothetical monoprotic acids HA(aq) and HB(aq) are used to prepare 1.0-L stock solutions of each acid. a Write the chemical reactions for these acids in water. What are the concentrations of the two acid solutions? b One of these acids is a strong acid, and one is weak. What could you measure that would tell you which acid was strong and which was weak? c Say that the HA(aq) solution has a pH of 3.7. Is this the stronger of the two acids? How did you arrive at your answer? d What is the concentration of A(aq) in the HA solution described in part c? e If HB(aq) is a strong acid, what is the hydronium-ion concentration? f In the solution of HB(aq), which of the following would you expect to be in the greatest concentration: H3O+(aq), B(aq), HB(aq), or OH(aq)? How did you decide? g In the solution of HA(aq), which of the following would you expect to be in the greatest concentration: H3O+(aq), A+(aq), HA(aq), or OH(aq)? How did you decide? h Say you add 1.0 L of pure water to a solution of HB. Would this water addition make the solution more acidic, make it less acidic, or not change the acidity of the original solution? Be sure to fully justify your answer. i You prepare a 1.0-L solution of HA. You then take a 200-mL sample of this solution and place it into a separate container. Would this 200 mL sample be more acidic, be less acidic, or have the same acidity as the original 1.0-L solution of HA(aq)? Be sure to support your answer.
An aqueous solution contains formic acid and formate ion. Determine the direction in which the pH will change if each of the following chemicals is added to the solution. (a) HCl (b) NaHSO4 (c) CH3COONa (d) KBr (e) H2O
What is a salt? List some anions that behave as weak bases in water. List some anions that have no basic properties in water. List some cations that behave as weak acids in water. List some cations that have no acidic properties in water. Using these lists, give some formulas for salts that have only weak base properties in water. What strategy would you use to solve for the pH of these basic salt solutions? Identify some salts that have only weak acid properties in water. What strategy would you use to solve for the pH of these acidic salt solutions? Identify some salts that have no acidic or basic properties in water (produce neutral solutions). When a salt contains both a weak acid ion and a weak base ion, how do you predict whether the solution pH is acidic, basic, or neutral?
Write an equation to describe the proton transfer that occurs when each of these acids is added to water. (a) HCO3 (b) HCl (c) CH3COOH (d) HCN
Calculate the pH of each of the following solutions. (a) 10.0 mL of 0.300 M hydrofluoric acid plus 30.0 mL of 0.100 M sodium hydroxide (b) 100.0 mL of 0.250 M ammonia plus 50.0 mL of 0.100 M hydrochloric acid (c) 25.0 mL of 0.200 M sulfuric acid plus 50.0 mL of 0.400 M sodium hydroxide
Two strategies are also followed when solving for the pH of a base in water. What is the strategy for calculating the pH of a strong base in water? List the strong bases mentioned in the text that should be committed to memory. Why is calculating the pH of Ca(OH)2 solutions a little more difficult than calculating the pH of NaOH solutions? Most bases are weak bases. The presence of what element most commonly results in basic properties for an organic compound? What is present on this element in compounds that allows it to accept a proton? Table 13-3 and Appendix 5 of the text list Kb values for some weak bases. What strategy is used to solve for the pH of a weak base in water? What assumptions are made when solving for the pH of weak base solutions? If the 5% rule fails, how do you calculate the pH of a weak base in water?
Use the same symbols as in Question 61 ( = anion, =OH) for the box below. (a) Fill in a similar box (representing one liter of the same solution) after 2 mol of H+ (2) have been added. Indicate whether the resulting solution is an acid, base, or buffer. (b) Follow the directions of part (a) for the resulting solution after 2 mol of OH- (2 ) have been added. (c) Follow the directions of part (a) for the resulting solution after 5 mol of OH- (5 ) have been added. (Hint: Write the equation for the reaction before you draw the results.)
Classify each of the following salts as a strong acid strong base salt, a strong acidweak base salt, a weak acidstrong base salt, or a weak acidweak base salt. a. NaCl b. KC2H3O2 c. NH4Br d. Ba(NO3)2
Each of the following statements concerns a 0.10 M solution of a weak organic base, B. Briefly describe why each statement is either true or false. a [B] is approximately equal to 0.10 M. b [B] is much greater than [HB+]. c [H3O+] is greater than [HB+]. d The pH is 13. e [HB+] is approximately equal to [OH]. f [OH] equals 0.10 M.
Acids You make a solution by dissolving 0.0010 mol of HCl in enough water to make 1.0 L of solution. a Write the chemical equation for the reaction of HCl(aq) and water. b Without performing calculations, give a rough estimate of the pH of the HCl solution. Justify your answer. c Calculate the H3O+ concentration and the pH of the solution. d Is there any concentration of the base OH present in this solution of HCl(aq)? If so, where did it come from? e If you increase the OH concentration of the solution by adding NaOH, does the H3O+ concentration change? If you think it does, explain why this change occurs and whether the H3O+ concentration increases or decreases. f If you were to measure the pH of 10 drops of the original HCl solution, would you expect it to be different from the pH of the entire sample? Explain. g Explain how two different volumes of your original HCl solution can have the same pH yet contain different moles of H3O+. h If 1.0 L of pure water were added to the HCl solution, would this have any impact on the pH? Explain.