acids, bases and ph chapter 19. compounds that become acids when dissolved in water general formula:...

Acids, Bases and pH

Chapter 19

Compounds That Become Acids When Dissolved in Water

• General Formula: HX

H+ X-

monatomic or polyatomic anion

Naming Acids (p. 250)Binary acidsHydro_______ic AcidHCl: Hydrochloric acidHBr: Hydrobromic acidHS: Hydrosulfuric acid

Oxyacids ite becomes ousAcid from chlorite: HClO2 = chlorous acid

Acid from phosphite:H3PO3 = phosphorous acid

ate becomes icAcid from sulfate: H2SO4 = sulfuric acid


Your turn:

HBr

HNO2

HNO3


Your turn:

HBr hydrobromic acid

HNO2

nitrous acidHNO3

nitric acid

Practice

Name or write formulas for the following acids:1. Phosphoric Acid 5. HClO4

2. Hydrochloric Acid 6. HI3. Chlorous Acid 7. H2S

4. Sulfurous Acid 8. HC2H3O2

9. Write the balanced formula, total ionic and net ionic equations for the acid base neutralization reaction that occurs when aqueous sulfuric acid is mixed with aqueous potassium hydroxide

Practice

Name or write formulas for the following acids:1. phosphoric acid H3PO4

2. hydrochloric acid HCl3. chlorous Acid HClO2

4. sulfurous Acid H2SO3

5. HClO4 perchloric acid

6. HI hydroiodic acid7. H2S hydrosulfuric acid

8. HC2H3O2 acetic acid

Practice

9. Write the balanced formula, total ionic and net ionic equations for the acid base neutralization reaction that occurs when aqueous sulfuric acid is mixed with aqueous potassium hydroxide

(put answer on front whiteboard)

Properties of Acids and BasesAcids Bases

Taste sour Taste bitterFeel wet Feel slippery

Turn litmus RED Turn litmus BLUEConduct electricity Conduct electricity

React with most metals Do NOT react with most metalsContain more H+ than OH- Contain more OH- than H+

pH between 0 and 7 pH between 7 and 14

strong acid + strong base salt + H2O

Arrhenius acids and bases Acid: compound containing H that ionizes to

yield H+ in solution

HCl(g) H+(aq) + Cl-

(aq)

HCl(g) + H2O(l) H3O+(aq) + Cl-

(aq)

Base: compound containing OH that ionizes to yield OH- in solution

NaOH(s) Na+(aq) + OH-

(aq)

*Note: Every Arrhenius acid/base is also a Brønsted-Lowry acid/base.

H2O

H2O

Acid-Base Reactions

In an acid-base reaction, the acid donates a proton (H+) to the base.

Autoionization of Water

In pure water :[H3O+] = 1.0 x 10-7 M AND [OH-] = 1.0 x 10-7 M

If we add acid [H3O+] increases and [OH-] decreases.

[H3O+] = 1.0 x 10-4 M [OH-] = 1.0 x 10-10 M

If we add base, the reverse is true:

[H3O+] = 1.0 x 10-10 M [OH-] = 1.0 x 10-4 M

What is the product of [H3O+] x [OH-] in each case?

H2O + H2O H3O+ + OH-

The pH Scale

pOH = - log [OH-] = - log (1.0 x 10-7) = -(-7) = 7

pH = - log [H+] = - log (1.0 x 10-7) = -(-7) = 7

Pure Water

basis of neutral pH 7:[H+] = [OH-]

Concentration, pH and pOH(for strong acids and bases)

Concentration is given in terms of molarity (M)

Concentration of H+ = [H+] = = 0.0100 M

In scientific notation: [H+] = 1.00 x 10-2 M

Find pH: pH = -log[1.00 x 10-2 M] pH = 2

Find pOH: pH + pOH = 14 pOH = 12

Find [OH-]: [OH-] = 10-pOH = 10-12 [OH-] = 1.00 x 10-12 M

0.0100 moles H+

L solution

Converting between Concentration and pH

pH pOH[H+] [OH-]10-pOH

-log[H+ ] 14-pH

pHpOH [H+][OH-] 10-pH

-log[OH- ] 14-pOH

1.00 x 10-4 M 4 10 1.00 x 10-10 M

1.00 x 10-11 M 11 3 1.00 x 10-3 M

PracticepH + pOH = 14; pH = -log[H+]; pOH = -log[OH-]

When pH = 2 [H+] = _____________M pOH = ____________ [OH-] = ____________M

When pOH = 8 [OH-] = ___________ M pH = _____________[H+] = ____________ M[H+] = 1.0 x 10-3 M What is the [OH-]?

More Practice (HW)

1. What is the pH of a solution with a [H+] of 10-8 M?

2. What is the pOH of a solution with a [OH-] of 10-11 M?

3. What is the pH of a solution with a [OH-] of 10-2 M?

4. What is the pOH of a solution with a [H+] = 10-5 M?

5. Which is more acidic, a solution with a pH of 6 or one

with a pH of 9?

6. Which is more basic, a solution with a pOH of 7 or one

with a pOH of 12?


with a pOH of 10?

8. Which is more basic, a solution with a pH of 8 or one

with a pOH of 12?

More Practice

1. What is the pH of a solution with a [H+] of 10-8 M? 8

2. What is the pOH of a solution with a [OH-] of 10-11 M? 11

3. What is the pH of a solution with a [OH-] of 10-2 M? 12

4. What is the pOH of a solution with a [H+] = 10-5 M? 9


with a pH of 9? pH of 6

6. Which is more basic, a solution with a pOH of 7 or one

with a pOH of 12? pOH of 7


with a pOH of 10? pOH of 10

8. Which is more basic, a solution with a pH of 8 or one

with a pOH of 12? pH of 8

More Practice

9. Stomach contents can have a pH of 3.

Are stomach contents acidic, basic or neutral?

10. Pure water has a pOH of 7. Is pure water acidic, basic or neutral?

11. Normal rain has a pH of approximately 6. Is normal rain strongly acidic, slightly acidic, neutral, slightly basic, or strongly basic?

12. Acid precipitation is often a problem in industrialized areas.

What might you expect the pH of acid rain to be?

More Practice

9. Stomach contents can have a pH of 3. Are stomach contents acidic, basic or neutral? acidic

10. Pure water has a pOH of 7. Is pure water acidic, basic or neutral? neutral

11. Normal rain has a pH of approximately 6. Is normal rain strongly acidic, slightly acidic, neutral, slightly basic, or strongly basic?

slightly acidic

12. Acid precipitation is often a problem in industrialized areas.

What might you expect the pH of acid rain to be? < 6

Strong acid or base – ionizes/dissociates completely in water[H+] or [OH-] = conc. of acid or base. e.g. HCl, NaOH. 5 units of acid – 5 out of 5 dissociated

H+ Cl- H+ Cl- H+ Cl- H+ Cl- H+ Cl- Weak acid or base – ionizes/dissociates only partially in water [H+] or [OH-] < conc. of acid or base. e.g. HC2H3O2, NH3

5 units – only 1 out of 5 dissociated

HC2H3O2 HC2H3O2 HC2H3O2 HC2H3O2 H+ C2H3O2-

Strength of Acids and Bases

© 2009, Prentice-Hall, Inc.

Practice

The diagrams below represent aqueous solutions of three acids (HX, HY, and HZ) with water molecules omitted for clarity. Rank them from strongest to weakest.

Strengths of Acids and Bases

Strong ¹ concentrated

Weak ¹ dilute

A concentrated weak acid (or base) may have the same pH as a dilute strong acid (or base).

Strong vs. Weak Demo

Strong acid:HCl + H2O Cl- + H3O+

1.0 x 10-2 M ? MpH = ?

Weak acid:HC2H3O2 + H2O ↔ C2H3O2

- + H3O+

1.0 x 10-2 M ? MpH = ?

Strong base:NaOH + H2O Na+ + OH-

1.0 x 10-2 M ? M pH = ?

Weak base: NH3 + H2O ↔ NH4

+ + OH-

1.0 x 10-2 M ? M pH = ?

Strong and Dilute vs. Weak and Concentrated

Acids:Strong HCl Weak HC2H3O2 Weak HC2H3O2

Dilute Dilute Conc 100 x0.01 M 0.01 M 1MpH = pH = pH =

Bases:Strong NaOH Weak NH3 Weak NH3

Dilute Dilute Conc 100 x0.01M 0.10 M 1M pH = pH = pH =

What do you think?

Table saltVinegarRubbing alcoholWindow CleanerDistilled water

Lemon juiceSoapDrain cleanerApplesauceBlood

Are the following acidic, basic or neutral?

What is the difference between a strong acid and a concentrated acid?

A weak acid and a dilute acid?

Warm up1. Write formulas for the following acids:

a) hydroiodic acid

b) chlorous acid

c) chloric acid

d) perchloric acid (Honors)

e) hypochlorous acid (Honors)

f) phosphoric acid

g) phosphorous acid

Warm up1. Write formulas for the following acids:

a) hydroiodic acid HI

b) chlorous acid HClO2

c) chloric acid HClO3

d) perchloric acid HClO4 (Honors)

e) hypochlorous acid HClO (Honors)

f) phosphoric acid H3PO4

g) phosphorous acid H3PO3 (Honors)

Warmup• What is the pH of a solution of nitric acid (strong acid) that has a

concentration of 10-4 M?4

• What is its pOH? 10

• Concentration of OH-?10-10 M

• Compare strong acids with weak acids. Use concentration, extent of ionization, and pH in your answer.

• Strong acids ionize completely in water, so the concentration of H+ is the same as the compound itself. A weak acid of equal concentration (molarity) will have a lower concentration of H+, and thus a higher pH.


Neutralization ReactionsGenerally, when solutions of an acid and a base are combined, the products are a salt and water.

CH3COOH (aq) + NaOH (aq) CH3COONa (aq) + H2O (l)


Neutralization ReactionsWhen a strong acid reacts with a strong base, the net ionic equation is…

HCl (aq) + NaOH (aq) NaCl (aq) + H2O (l)




H+ (aq) + Cl- (aq) + Na+ (aq) + OH-(aq)

Na+ (aq) + Cl- (aq) + H2O (l)




H+ (aq) + Cl- (aq) + Na+ (aq) + OH-(aq)

Na+ (aq) + Cl- (aq) + H2O (l)

H+ (aq) + OH- (aq) H2O (l)


Titration

Titration is an analytical technique in which one can calculate the concentration of a solute in a solution.


Titration

= A method of volumetric analysis in which a volume of one reagent is added to a known volume of another reagent slowly from a buret until an end point is reached. If one of the solutions has a known concentration, the concentration of the other can be calculated, via stoichiometry.


Titration

Standard solution = reagent solution of known concentration

Titrant = reagent solution of unknown concentration

Equivalence point = the point at which stoichiometrically equivalent quantities are brought together

End point = color change (v. close to equivalence point)


Change in appearance of a solution containing phenolphthalein as base indicator


Titration


Example Titration

• Predict the number of mL of ~0.10 M NaOH needed to neutralize 10.0 mL of 0.25 M HCl.

• We want to know the exact molarity of the NaOH solution.


Titration Practice ProblemsRemember: Moles are central!

1. In the titration of 35 mL of liquid drain cleaner containing NaOH, 50. mL of 0.40 M HCl must be added to reach the equivalence point. What is the molarity of the base in the cleaner?

(0.57 M)


Titration Practice ProblemsRemember: Moles are central!

2. A 20.0 mL sample of an HCl solution is titrated with 27.4 mL of a standard solution of Ba(OH)2.

The concentration of the standard is 0.0154 M. What is the molarity of the HCl?

(0.0422 M)

Brønsted-Lowry Acids and Bases (1923)

Acid: H+ (proton) donorBase: H+ (proton) acceptor

HCl + H2O H3O+ + Cl-

acid base conjugate conjugate acid base

Brønsted-Lowry Acids and Bases (1923)

NH3 + H2O D NH4+ + OH-

ammonia water ammonium ion hydroxide ion(B-L base) (B-L acid) (B-L acid) (B-L base)

base acid conjugate acid conjugate base

Conjugate Acid-Base Pairs

• Conjugate acid = species produced when a base accepts a hydrogen ion from an acid

• Conjugate base = species that results when an acid donates a hydrogen ion to a base

Identify the conjugate acid-base pairs:

• HClO + H2O D ClO- + H3O+

• HS- + H2O D H2S + OH-

• HPO42- + H2O D H2PO4

- + OH-

• HPO42- + H2O D PO4

3- + H3O+

• An amphoteric compound is able to act as either an

acid or a base. Which compounds in the above

equations are amphoteric?

acids, bases and ph chapter 19. compounds that become acids when dissolved in water general formula:...

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