1. Acids
Lesson 20
Subtle Items

3. Subtle Acid Items
1. Weak bases neutralize a strong acid as well as a strong base would.
HCl + NaOH
HCl + HCO3-
→ NaCl + HOH
→ H2CO3 + Cl-
Both reactions go to completion because of the strong acid.

4. 2. H3BO3
H2CO3
HCl  
triprotic
H3BO3 ⇌ H+ + H2BO3-
diprotic
H2CO3 ⇌ H+ + HCO3-
monoprotic
HCl → H+ + Cl-
Only lose one proton when in water!

5.  Which neutralizes more NaOH? H3BO3 or HCl?
H3BO NaOH → Na3BO HOH
HCl NaOH → NaCl + HOH

6.  3. Which determines acid strength? Molarity Ka is concentration
Molarity Ka
is concentration 
is strength as indicated in the acid chart

7.    4. Which determines the pH = -Log[H+] Ka determines the [H+]
= -Log[H+] Ka
determines the [H+] 
Molarity
determines the [H+] 
Temperature
affects the Ka 

8. 5. Pick the best conductor.
1 M NaCN 0.1 M HCl 0.1 M KOH 

9.  6. Pick the worst conductor. NaOH HCl NaCN NH3
NaOH HCl NaCN NH3 
Good Conductors are…..
Strong acids
Strong Bases
Soluble Salts

10. 1 mole H2CO3 and 1mole NaHCO3 are dissolved in
0.5 L of water.
  What kind of solution results in the above mixture?
Buffer
Write an equation for the equilibrium.
H2CO3 ⇋ H+ + HCO3-
Label each chemical species with a concentration.
2 M Low 2 M
What limits the ability to buffer against acid?
[HCO3-]
What limits the ability to buffer against base?
[H2CO3]

11. 8. Acid Base
  HF F-
H3BO3 H2BO3-
HCN CN-
Put an asterisk next to the strongest acid and base
What is the relationship between acid strength and strength of conjugate base? * *
Inverse

12. 9. What ions are in H2SO4 solution?
H2SO4 → H+ + HSO4-
HSO4- ⇌ H+ + SO42-
[ OH-]
because it is in water!

13. 10. Which titration will have the equivalence point with
10. Which titration will have the equivalence point with lowest conductivity?
HCl + NaOH →
H2SO Ba(OH)2 →
NaCl(aq) + HOH
High Solubility
BaSO4(s) HOH
Low Solubility
Lowest Conductivity

14.  11. What is the best acid for titrating 0.10 M NH3?
11. What is the best acid for titrating 0.10 M NH3?
M HCl 0.10 M HF
6.0 M HCl M HCl 
Must be strong and about the same molarity!

15. 12. HCl Molarity pH
10 M -1
1 M
0.1M 1 2
0.01M
0.001M 3
0.0001M 4

16. 13. A 0.00010 M acid has a pH of 4.0. Is the acid strong or weak?
Strong pH = -Log[ ] = 4.0
The pH is only at 1.0 M!

17. 14. A 0.0010 M acid has a pH of 4.0. Is the acid strong or weak?
Weak pH = -Log[0.0010] = 3.0
The pH is only at 1.0 M!

18.   15. HInd ⇌ H+ + Ind- It’s yellow in HCl and red in HCN
Assign each colour
Which is the stronger acid; HInd or HCN?
HCN + Ind- ⇌ HInd CN-
What is favoured?
Reactants
yellow
red  

19. 16. Describe the buffer present in human blood.
H2CO3 NaHCO3
17. What is stomach acid?
HCl
18 . What is battery acid?
H2SO4

20.  19. Match the Curve with the ReactionpH
Volume 1.0 M NH3 added 14 7 30 60 
A. 3HCl Al(OH)3 → AlCl HOH
B. HCl KOH → KCl + HOH
C. HCN KOH → KCN + HOH

21.  20. Match the Curve with the ReactionpH
Volume 1.0 M NH3 added 14 7 30 60
A. 3HCl Al(OH)3 → AlCl HOH
B. HCl KOH → KCl + HOH
C. HCN KOH → KCN + HOH 

22. 21. Write a reaction between NaHCO3 and NaHC2O4
HCO HC2O4- ⇌
H2CO C2O42-
Are the reactants or products favoured?
products

23. 0.10 M Weak Acid
0.10 M Weak Base x2 x2 Kw = Ka = Kb = Ka
0.10
0.10