Chemistry 12. Bronsted Acids and Bases

Transcription

1 Unit 4 Acids, Bases and Salts Chemistry 12 Tutorial 14 Solutions Bronsted Acids and Bases Answer to Question 1 on page 5 of Tutorial Complete equations for the following acids ionizing in water: a) HClO (g) + H 2 O (l) H 3 O + (aq) + ClO (aq) b) H 2 SO 4 (l) + H 2 O (l) H 3 O + (aq) + HSO 4 (aq) (you can see that only 1 H + is removed from the H 2 SO 4.) c) CH 3 COOH (l) + H 2 O (l) H 3 O + (aq) + CH 3 COO (aq) d) HSO 4 (aq) + H 2 O (l) H 3 O + (aq) + SO 4 2 (aq) (When 1 H + is removed from the HSO 4, it leaves it s electron behind, thus the SO 4 ends up with a charge of 2) ************************************************************* Answers to Question 2 on page 8 of Tutorial Identify the acid and the base in the reactants of the following reactions: a) H 2 S + HCO 3 H 2 CO 3 + HS (H 2 S donates a proton to become HS ) acid base (HCO 3 accepts a proton to become H 2 CO 3 ) b) HS + HCO 3 CO H 2 S base acid c) HCOOH + HSO 3 H 2 SO 3 + HCOO acid base d) S 2 + H 2 PO 4 HPO HS base acid Tutorial 14 Solutions Page 1

2 Unit 4 Acids, Bases and Salts e) H 2 SO 3 + HCO 3 H 2 CO 3 + HSO 3 acid base f) NH H 2 O H 3 O + + NH 3 acid base ************************************************************* Answer to Question 3 on page 9 of Tutorial Identify acids and bases on the left side and the right side of the following equations: Hint: To get the ones on the right, pretend the reaction is going in reverse. a) H 3 BO 3 + NH 3 H 2 BO 3 + NH + 4 acid base base acid b) NO 2 + HIO 3 HNO 2 + IO 3 base acid acid base c) C 6 H 5 OH + OH C 6 H 5 O + H 2 O acid base base acid ************************************************************** Answers to Question 4 on pages 10 of Tutorial Identify the conjugate acidbase pairs in each of the following reactions: (NOTE: Pair 1 and Pair 2 could be exchanged and the answer would still be correct.) a) NH 3 + CH 3 COOH NH CH 3 COO Pair 1: (acid) CH 3 COOH (base) CH 3 COO Pair 2: (acid) NH + 4 (base) NH 3 b) H 2 SO 3 + H 2 PO 4 H 3 PO 4 + HSO 3 Pair 1: (acid) H 2 SO 3 (base) HSO 3 Pair 2: (acid) H 3 PO 4 (base) H 2 PO 4 Tutorial 14 Solutions Page 2

3 Unit 4 Acids, Bases and Salts c) HC 2 O 4 + HNO 2 NO 2 + H 2 C 2 O 4 Pair 1: (acid) HNO 2 (base) NO 2 Pair 2: (acid) H 2 C 2 O 4 (base) HC 2 O 4 d) Al(H 2 O) HCO 3 Al(H 2 O) 5 (OH) 2+ + H 2 CO 3 Pair 1: (acid) Al(H 2 O) 6 3+ (base) Al(H 2 O) 5 (OH) 2+ Pair 2: (acid) H 2 CO 3 (base) HCO 3 *************************************************************** Answers to Question 5 on Page 11 of Tutorial Find the conjugate acid of each of the following. Make sure you have the charges correct: a) CH 3 COO conjugate acid is... CH 3 COOH b) SO 4 2 conjugate acid is... HSO 4 c) H 2 O conjugate acid is... H 3 O + d) O 2 conjugate acid is... OH e) OH conjugate acid is... H 2 O f) HPO 4 2 conjugate acid is... H 2 PO 4 (Make sure you have the charge correct.) g) H 2 PO 4 conjugate acid is... H 3 PO 4 h) NH 3 conjugate acid is... NH 4 + *************************************************************** Answers to Question 6 on page 12 of Tutorial Find the conjugate base of each of the following. Make sure you have the charges correct: a) HNO 3 conjugate base is... NO 3 b) H 2 C 2 O 4 conjugate base is... HC 2 O 4 Tutorial 14 Solutions Page 3

4 Unit 4 Acids, Bases and Salts c) H 2 SO 3 conjugate base is... HSO 3 d) HNO 2 conjugate base is... NO 2 e) HClO 3 conjugate base is... ClO 3 f) H 2 O conjugate base is... OH g) OH conjugate base is... O 2 h) NH 4 + conjugate base is... NH 3 ************************************************************** Answer to Question 7 on page 15 of Tutorial a) Write the three equations showing the stepwise dissociation of arsenic acid H 3 AsO 4. Step 1: H 3 AsO 4(aq) + H 2 O (l) H 3 O + (aq) + H 2 AsO 4 (aq) Step 2: H 2 AsO 4 (aq) + H 2 O (l) H 3 O + (aq) + HAsO 4 2 (aq) Step 3: HAsO 4 2 (aq) + H 2 O (l) H 3 O + (aq) + AsO 4 3 (aq) b) Summarize this process by leaving out the H 3 O + s and H 2 O s like was done for phosphoric acid in the example right above this question. See if you can come up with names for all the ions! step 1 step 2 step 3 H 3 AsO 4 H 2 AsO 4 HAsO 2 4 AsO 3 4 arsenic acid dihydrogen arsenate monohydrogen arsenate arsenate Tutorial 14 Solutions Page 4

5 Unit 4 Acids, Bases and Salts Answer to Question 8 on page 17 of Tutorial a) Write the two steps in the dissociation of carbonic acid (H 2 CO 3 ). Step 1: H 2 CO 3(aq) + H 2 O (l) H 3 O + (aq) + HCO 3 (aq) Step 2: HCO 3 (aq) + H 2 O (l) H 3 O + (aq) + CO 3 2 (aq) b) Give the formula and the name for the amphiprotic anion formed in this process. Formula HCO 3 Name (you may use the acid chart.) hydrogen carbonate or bicarbonate ************************************************************ Answers to the SelfTest starting on page 17 of Tutorial What is meant by a hydronium ion? H 3 O + 2. How does a hydronium ion form in water? An H + ion attaches itself to a water molecule 3. A hydronium ion can also be called a hydrated proton. 4. Complete the equations for the ionization of the following acids in water: a) HClO 2(aq) + H 2 O (l) H 3 O + (aq) + ClO 2 (aq) b) HF (g) + H 2 O (l) H 3 O + (aq) + F (aq) c) HNO 2(aq) + H 2 O (l) H 3 O + (aq) + NO 2 (aq) d) HCOOH (l) + H 2 O (l) H 3 O + (aq) + HCOO (aq) 5. Give the Arrhenius definitions of the following: a) an acid a substance that releases H + ions (protons) in water. b) a base a substance that releases OH (hydroxide) ions in water. Tutorial 14 Solutions Page 5

6 Unit 4 Acids, Bases and Salts 6. Give the Bronsted definitions of the following: a) an acid any substance which donates (gives) a proton (H + ) to another substance b) a base any substance which accepts (takes) a proton (H + ) from another substance 7. Identify acids and bases on the left side and the right side of the following equations: a) C 6 H 5 OH + CO 2 3 HCO 3 + C 6 H 5 O acid base acid base b) H 2 PO 4 + H 2 SO 3 H 3 PO 4 + HSO 3 base acid acid base 8. Identify the conjugate acidbase pairs in each of the following reactions: a) NH 3 + H 2 SO 3 NH HSO 3 Pair 1: (acid) H 2 SO 3 (base) HSO 3 Pair 2: (acid) NH + 4 (base) NH 3 NOTE: It would still be correct if you had pair 1 and pair 2 exchanged. b) H 2 C 2 O 4 + H 2 PO 4 H 3 PO 4 + HC 2 O 4 Pair 1: (acid) H 2 C 2 O 4 (base) HC 2 O 4 Pair 2: (acid) H 3 PO 4 (base) H 2 PO 4 NOTE: It would still be correct if you had pair 1 and pair 2 exchanged. c) HC 2 O 4 + CH 3 COOH CH 3 COO + H 2 C 2 O 4 Pair 1: (acid) CH 3 COOH (base) CH 3 COO Pair 2: (acid) H 2 C 2 O 4 (base) HC 2 O 4 NOTE: It would still be correct if you had pair 1 and pair 2 exchanged. Tutorial 14 Solutions Page 6

7 Unit 4 Acids, Bases and Salts 9. Find the conjugate acid of each of the following. Make sure you have the charges correct: a) HCOO conjugate acid is... HCOOH b) PO 3 4 conjugate acid is... HPO 2 4 c) OH conjugate acid is... H 2 O d) H 2 BO 3 conjugate acid is... H 3 BO 3 e) H 2 O conjugate acid is... H 3 O Find the conjugate base of each of the following. Make sure you have the charges correct: a) H 2 CO 3 conjugate base is... HCO 3 b) HC 2 O 4 conjugate base is... C 2 O 2 4 c) HSO 3 conjugate base is... SO 2 3 d) HNO 2 conjugate base is... NO 2 e) H 2 PO 4 conjugate base is... HPO a) Write the three equations showing the stepwise dissociation of boric acid (H 3 BO 3 ). Step 1: H 3 BO 3(aq) + H 2 O (l) H 3 O + (aq) + H 2 BO 3 (aq) Step 2: H 2 BO 3 (aq) + H 2 O (l) H 3 O + (aq) + HBO 3 2 (aq) Step 3: HBO 3 2 (aq) + H 2 O (l) H 3 O + (aq) + BO 3 3 (aq) b) Give the formulas and the names for the amphiprotic anions formed in this process. Formula H 2 BO 3 Formula HBO 3 2 Name dihydrogen borate Name monohydrogen borate Tutorial 14 Solutions Page 7

8 Unit 4 Acids, Bases and Salts 12. If the ion HPO 3 2 was to act an acid, it would form PO If the ion HPO 3 2 was to act a base, it would form H 2 PO How can you recognize an amphiprotic anion? It has at least one H and it has a negative charge This is the end of Tutorial 14 Solutions ********************************************************** Tutorial 14 Solutions Page 8