Chem 104 exam

Homework Acid/Base VII » Acid/Base VII - Problem 2 of 2 For the next three problems, consider 1.0 L of a solution which is 0.55 M HC2H3O2 and 0.2 M NaC2H3O2 (Ka for HC2H3O2 = 1.8 x 10-5). Assume 2 significant figures in all of the given concentrations so that you should calculate all of the following pH values to two decimal places. 1. Calculate the pH of this solution. 2. Calculate the pH after 0.10 mol of HCl has been added to the original solution. Assume no volume change on addition of HCl. 3. Calculate the pH after 0.20 mol of NaOH has been added to the original buffer solution. Assume no volume change on addition of NaOH.

1. 4.31 2.3.93 3.4.80

Prelecture_assignments » acid_base_VI_prelect Arrange the following 0.4 M solutions in order of increasing pH: KNO2 < C6H5NH3NO3 < KI < Ca(OH)2 HClO2

HClO2 < C6H5NH3NO3 < KI < KNO2 < Ca(OH)2

Rank the following 0.10 M solutions in order of increasing pH: HClO4 NaCl NH3 KOH HF

HClO4 < HF < NaCl < NH3 < KOH

Rank the following 0.10 M solutions in order of increasing pH (lowest pH to highest pH): HOCl HNO3 HF NaCl

HNO3 < HF < HOCl < NaCl

Homework Acid/Base VIII » Acid/Base VIII - Problem 1 For the next three problems, consider 1.0 L of a solution which is 0.55 M HF and 0.2 M NaF (Ka for HF = 7.2 x 10-4). Assume 2 significant figures in all of the given concentrations so that you should calculate all of the following pH values to two decimal places. 1. Calculate the pH of this solution. 2. Calculate the pH after 0.10 mol of HCl has been added to the original solution. Assume no volume change on addition of HCl. 3. Calculate the pH after 0.20 mol of NaOH has been added to the original buffer solution. Assume no volume change on addition of NaOH.

1.2.70 2.2.33 3.3.20

At what volume (in mL) of NaOH added does the pH of the resulting solution equal 7.00? Include the units of mL in your answer.

NaOH = 50.0 mL

Consider the titration of 100.0 mL of 0.100 M HNO3 by 0.200 M NaOH. Calculate the pH after 41.9 mL of NaOH has been added.

1.94

Calculate the pH of a 0.6 M solution of NaCN (Ka for HCN = 6.2 x 10-10). Record your pH value to 2 decimal places.

11.49

Calculate the pH of a 0.87 M solution of C6H5NH3NO3 (Kb for C6H5NH2 = 3.8 x 10-10). Record your pH value to 2 decimal places.

2.32

Consider 0.10 M solutions of the following substances. Rank the solutions in order of increasing pH where 1 is the solution with the lowest pH and 7 is the solution with the highest pH. Reference the Ka and Kb Tables , and think about the acid/base properties of each species present. NaCN,C5H5N, H2HHH3Cl, NaOH, CaCl2, HOI, HClO4

6: NaCN 5: C5H5N 2: H2NNH3Cl 7: NaOH 4: CaCl2 3: HOI 1: HClO4

Calculate the pH of a 0.41 M solution of Ca(ClO4)2. Record your pH value to 2 decimal places.

7.00

Consider a buffer solution consisting of CH3NH3Cl and CH3NH2. Which of the following statements are true concerning this solution? (Ka for CH3NH3+ = 2.3 x 10 -11). If HCl were added to the initial buffer solution, then the [CH3NH3+] would decrease. If [CH3NH3+] < [CH3NH2], then the [H+] is larger than the Ka value. If [CH3NH3+] <[CH3NH2], then pH is larger than the pKa value. Adding more [CH3NH3+] to the initial buffer solution will decrease the pH. A solution consisting of 0.1 M CH3NH3Cl and 0.1 M CH3NH2 would be a more effective buffer than one containing 1.5 M CH3NH3Cl and 1.5 M CH3NH2 If [CH3NH3+] = [CH3NH2], then pH = 7.00.

False: If HCl were added to the initial buffer solution, then the [CH3NH3+] would decrease. False: If [CH3NH3+] < [CH3NH2], then the [H+] is larger than the Ka value. True: If [CH3NH3+] <[CH3NH2], then pH is larger than the pKa value. True: Adding more [CH3NH3+] to the initial buffer solution will decrease the pH. False: A solution consisting of 0.1 M CH3NH3Cl and 0.1 M CH3NH2 would be a more effective buffer than one containing 1.5 M CH3NH3Cl and 1.5 M CH3NH2 False: If [CH3NH3+] = [CH3NH2], then pH = 7.00.

Consider the following questions about polyprotic acids and determine if each statement is true or false.

false: For most polyprotic acids, each proton dissociation can not be looked at separately true: For most polyprotic acids Ka1 largely determines the pH of the solution false: for polyprotic acids Ka1 is typically much smaller than Ka2

Which of the following statements about the acid/base properties of salts are true? Which are false?

false: conjugate bases of weak acids will be acidic false: Cations found in strong bases (like Na+) make the pH of a solution acidic false: conjugate acids of weak bases will be basic true: Anions found in strong acids (like Cl-) do not change the pH of a solution

Consider a solution of 0.55 M NH3 (Kb = 1.8×10-5). Decide if each of the following is a major or minor species in the solution. NH4+, OH-,H+,H2O,NH3 What is the pH?

minor: NH4+ minor: OH− minor: H+ major: H2O major: NH3 pH=11.50

Homework Acid/Base VII » Acid/Base VII - Problem 1 of 2 Consider 0.25 M solutions of the following salts. For each salt, indicate whether the solution is acidic, basic, or neutral. Sr(ClO4)2 ,NaCl,Sr(OC6H5)2 ,C5H5NHBr ,NH4Cl ,NaCN

neutral: Sr(ClO4)2 neutral: NaCl basic: Sr(OC6H5)2 acidic: C5H5NHBr acidic: NH4Cl basic: NaCN

Consider the following acids and bases: HCO2H Ka=1.8x10-4 HONH2 Kb=1.1x10-8 HOBr Ka=2.0x10-9 (C2H5)2NH Kb=1.3x10-3 Which combination of the following substances would make the best choice to prepare a pH=6.0 buffer solution?

yes: HONH2 no: HOBr no: (C2H5)2NH2Cl no: KCO2H no: (C2H5)2NH yes: HONH3NO3 no: HCO2H no: NaOBr