AcidsLesson 20

Subtle Items

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.

2. H3BO3

H2CO3

HCl  

triprotic H3BO3 ⇌ H+ + H2BO3-

diprotic H2CO3 ⇌ H+ + HCO3-

monoprotic HCl → H+ + Cl-

Only lose one proton when in water!

Which neutralizes more NaOH? H3BO3 or HCl?

H3BO3 + 3NaOH → Na3BO3 + 3HOH

HCl + 1NaOH → NaCl + HOH

3. Which determines acid strength? 

Molarity

Ka is strength as indicated in the acid chart

is concentration

4. Which determines the pH 

= -Log[H+]

determines the [H+]

determines the [H+]

affects the Ka

Ka

Molarity

Temperature

5. Pick the best conductor. 

1 M NaCN 0.1 M HCl 0.1 M KOH

6. Pick the worst conductor. 

NaOH HCl NaCN NH3

Good Conductors are…..

Strong acids

Strong Bases

Soluble Salts

7. 1 mole H2CO3 and 1mole NaHCO3 are dissolved in

0.5 L of water.

  What kind of solution results in the above mixture?BufferWrite an equation for the equilibrium.H2CO3 ⇋ H+ + HCO3

-

Label each chemical species with a concentration. 2 M Low 2 MWhat limits the ability to buffer against acid?[HCO3

-]What limits the ability to buffer against base?[H2CO3]

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

9. What ions are in H2SO4 solution?

 H2SO4 → H+ + HSO4

-

HSO4- ⇌ H+ + SO4

2-

[ OH-]

because it is in water!

BaSO4(s) + 2HOH

10. Which titration will have the equivalence point with lowest conductivity?

 HCl + NaOH →

 

H2SO4 + Ba(OH)2 →

NaCl(aq) + HOH

High Solubility

Low Solubility

Lowest Conductivity

 

11. What is the best acid for titrating 0.10 M NH3?

 0.00010 M HCl 0.10 M HF6.0 M HCl 0.10 M HCl

 

Must be strong and about the same molarity!

12. HCl Molarity pH

1 M 0

0.1M 1

0.01M 2

0.001M 3

0.0001M 4

10 M -1

13.A 0.00010 M acid has a pH of 4.0. Is the acid strong or weak?

Strong pH = -Log[0.00010] = 4.0

The pH is only at 1.0 M!

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!

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

16. Describe the buffer present in human blood.

H2CO3 NaHCO3

17. What is stomach acid?

HCl

18 . What is battery acid?

H2SO4

pH

Volume 1.0 M NH3 added

14

7

00 30 60

19. Match the Curve with the Reaction

A. 3HCl + Al(OH)3 → AlCl3 + 3HOHB. HCl + KOH → KCl + HOHC. HCN + KOH → KCN + HOH

pH

Volume 1.0 M NH3 added

14

7

00 30 60

A. 3HCl + Al(OH)3 → AlCl3 + 3HOHB. HCl + KOH → KCl + HOHC. HCN + KOH → KCN + HOH

20. Match the Curve with the Reaction

21. Write a reaction between NaHCO3 and NaHC2O4

HCO3- + HC2O4

- H2CO3 + C2O42- ⇌

Are the reactants or products favoured?

products

0.10 M Weak Acid

x2

Ka0.10

0.10 M Weak Base

x2

Kb0.10

Kw

Ka== =