Exam Practice. Chapters

Transcription

1 Exam Practice Chapters

2 Chapter 16 Chemical Equilibrium Concepts of: Weak bases Percent ionization Relationship between K a and K b Using structure to approximate strength of acids Strength of strong acids Acid/basic/neutrality of salts 2

3 1. What is the equilibrium reaction, the equation for the equilibrium constant and the value for the constant for the weak base, ethylamine? Similar to Chapter 16 practice #9 CH CH NH aq H O l CH CH NH aq OH aq K b CH CH NH OH CH CH NH What is the poh and ph of M ethylamine? poh = 1.735; ph = Similar to Chapter 16 practice #10 3. If an basic solution has an initial concentration of M and a ph at equilibrium of 11.58, what is the K b of this weak acid? 8.8x10 5 Is this acid stronger or weaker than the nitrite ion? Similar to Chapter 16 practice #11 3

4 1. Give the complimentary equilibrium reaction, equation for the equilibrium constant, and value of the constant for the conjugate of the weak acids and bases for formic acid and ethylamine a CH 3CH 2NH3 HCOOH OH 2 b CH CH NH CH CH NH aq H aq K HCOO aq H O l HCOOH aq OH aq K Similar to Chapter 16 practice #12 2. Identify the salts as acidic, basic or neutral. NaNO 3 neutral NH 4 NO 3 acidic NaNO 2 basic NH 4 NO 2 acidic Similar to Chapter 16 practice #13 CH CH NH H 11 HCOO 4

5 1. Sulfur trioxide is an acidic oxide while sodium oxide is a basic oxide. What are the balanced equations (reacting with water) that show these statements to be true? SO 3 (g) + H 2 O(l) H 2 SO 4 (aq) Na 2 O(s) + H 2 O(l) 2NaOH(aq) No similar problems in practice (similar to Chang, 16.83) 2. For the reaction of sulfur trioxide and water, what is the Lewis acid and the Lewis base? SO 3 is the Lewis acid and water is the Lewis base No similar problems in practice (similar to Chang, 16.79) 5

6 Chapter 17 Chemical Equilibrium Concepts of: Buffers: What is a buffer What makes a buffer How to make a buffer How a buffer reacts pk a and pk b Titrations: Weak vs. strong acid/base Initial ph Buffer region Equivalence point Excess titrant 6

7 Chapter 17 Chemical Equilibrium Concepts of: Solubility Equilibria: Saturated solutions Solubility product constant Molar solubility Q and K: predicting a precipitation reaction Common ion effect Selective precipitation Formation constants and the formation of complex ions Qualitative analysis 7

8 1. What is the pk a benzoic acid (4.19) and formic acid (3.77)? Which acid is stronger? Formic acid Similar to Chapter 17 practice #1 2. What is the pk b of the conjugate base of benzoic acid (9.81) and formic acid (10.23)? Which base is stronger? Conjugate base of benzoic acid Similar to Chapter 17 practice #2 3. What is the ph of a solution made by combining 25.0 ml of M formic acid with 35.0 ml of M sodium formate? 3.86 Similar to Chapter 17 practice #3 4. What is the ph of a solution made by combining 18.5 ml of M nitric acid with 35.0 ml of M sodium formate? 3.60 Similar to Chapter 17 practice #3 8

9 1. For the buffer (number 4, previous slide), what volume of a M solution of hydrochloric acid would be added to decrease the ph by 0.10? 13.8 ml Similar to Chapter 17 practice #5 2. For the buffer (number 4, previous slide), what is the ph after 5.0 ml of a M HNO 3 has been added? 3.56 Similar to Chapter 17 practice #5 3. For the buffer (number 4, previous slide), what is the ph after 5.0 ml of a M NaOH has been added? 3.64 Similar to Chapter 17 practice #7 9

10 You are going to titrate ml of 1.00 M hydrochloric acid with M sodium hydroxide. what is the initial ph before any titrant has been added? 0.00 what is the ph when 15.5 ml of the titrant has been added? what volume of the titrant is needed at the equivalence point? 33.3 ml what is the ph at the equivalence point? 7 what is the ph when 40.0 ml of the titrant has been added? what does the titration curve look like? Figure 17.4 Similar to Chapter 17 practice #8 10

11 You are going to titrate ml of 1.00 M methyl amine with M hydrochloric acid. what is the initial ph before any titrant has been added? what is the ph when 15.5 ml of the titrant has been added? what volume of the titrant is needed at the equivalence point? 33.3 ml what is the ph at the equivalence point? 5.51 what is the ph when 40.0 ml of the titrant has been added? 1.11 what does the titration curve look like? Figure 17.6 Similar to Chapter 17 practice #10 11

12 1. What is the reaction for a saturated solution of iron(iii) hydroxide, iron(ii) hydroxide and silver hydroxide? Fe(OH) 3 (s) Fe 3+ (aq) + 3OH (aq) Fe(OH) 2 (s) Fe 2+ (aq) + 2OH (aq) AgOH(s) Ag + (aq) + OH (aq) Similar to Chapter 17 practice #11 2. What are the product solubility constants for the reactions in number 1? K sp (Fe(OH) 3 ) = 1.1x10 36 K sp (Fe(OH) 2 ) = 1.6x10 14 K sp (AgOH) = 1.5x10 8 Similar to Chapter 17 practice #12 3. What are the molar solubilities for the salts in number 1? Fe(OH) 3 = 4.5x10 10 M Fe(OH) 2 = 1.6x10 5 M AgOH= 1.2x10 4 M Similar to Chapter 17 practice #13 4. What is the concentration of each metal ion in M sodium hydroxide? Fe 3+ = 1.8x10 36 M Fe 2+ = 2.2x10 14 M Ag + = 1.8x10 8 M Similar to Chapter 17 practice #15 5. When equal volumes of M sodium hydroxide and M metal nitrates are combined, what will happen? ppt for both iron hydroxides Similar to Chapter 17 practice #16 12

13 For a solution 1.0 L of M iron(iii) nitrate, iron(ii) nitrate and silver nitrate, when adding concentrated sodium hydroxide (such that adding the sodium hydroxide will not change the total volume): which salt will precipitate first? Fe(OH) 3 which salt will precipitate second? AgOH which salt will precipitate last? Fe(OH) 2 what is the concentration of the first metal ion that precipitated when the second salt begins to precipitate? 4.1x10 14 M what is the concentration of the second metal ion that precipitated when the third salt begins to precipitate? M can these salts be selectively precipitated? Fe(OH) 3 yes but AgOH and Fe(OH) 2 cannot Similar to Chapter 17 practice #17 13