Chapter 19: Acids/Bases Properties of an Acid: 1. Taste sour or tart 2. Electrolytic in solution (will conduct electricity when dissociated): a. strong.

Chapter 19: Acids/Bases

Properties of an Acid:

1. Taste sour or tart

2. Electrolytic in solution (will conduct electricity when dissociated):

a. strong acid = strong electrolyte

b. weak acid = weak electrolyte

3. React w/ metal produces H2

4. Reacts w/ OH for neutralization

Properties of Bases:

1. Feels slippery like soaps

2. Taste bitter

3. Electrolytes in solution

a. strong bases = strong electrolyte

b. weak bases = weak electrolyte

4. Reacts w/ acids to neutralize

Types of Acids/Bases

Lewis Acid: Accepts an electron pair.

Lewis Base: Donates an electron pair.

Bronsted/Lowery Acid: proton donor (H+)

Bronsted/Lowery Base: proton acceptor (H+)

*Arrhenius Acids: contain hydrogens and produces H+

*Arrhenius Base: produces hydroxide ions (OH-)

Naming Acids

1. Binary Acids: formed by the bonding of a hydrogen to a simple anion (Cl-, F-, S2-)

hydro - root - ic

HCl - hydro chlor ic (hydrochloric acid)

HBr - hydro brom ic (hydrobromic acid)

H2S - hydro sulfur ic (hydrosulfuric acid)

2. Ternary Acids: formed by the bonding of H+ to a polyatomic ion

-ate -ic, ite -ous (NEVER A HYDRO-)

HNO2 : NO2 is nitrite, so the root is nitr- ending in -ous.

Nitrous acidH3PO4 : PO4 is phosphate, so the root is phosphor- ending in -ic.

Phosphoric acid

Use your reference page for the anion roots!

Practice ProblemsName or write the formula for the following

1. Acetic acid 2. Cyanic acid

3. Nitric acid 4. Hydroiodic acid

5. Boric acid 6. Sulfuric acid

7. HBr 8. H2SO4

9. H2CO3 10. HF

Naming Bases

Bases are compounds the produce hydroxide ions (OH-) when dissolved in water.

Element name then hydroxide

NaOH :

Sodium hydroxide

Fe(OH)3 :

Iron (III) hydroxide

Bases

CuOH :

Copper (I) hydroxide

Cu(OH)2 :

Copper (II) hydroxide

Strength of Acids and Bases

The strength of an acid or base is defined by the dissociation of the acid or base.

Strong Acids and Base = 100% dissociation

Weaker Acids and Bases = less than 100%

*there are therefore degrees of weak defined by a ratio of dissociation, Ka

& Kb.

Concentration defines strength.

How is concentration expressed?

Molarity

Molarity: expression of concentration.

Molarity = # of moles of solute

# of liters of solution

M = moles/liter

1. What is the molarity of 3.65 g of HCl dissolved to a volume of 2 L?

*Convert mass to moles

*Calculate the molarity

Molarity: Sample Problems

1. What is the molarity of a solution of sulfuric acid when 49.04 g of sulfuric acid is dissolved in 250 ml of water?

2. What mass of barium hydroxide is needed to make 2.5 L of a 0.06 molar solution?

3. What is the molarity of a solution made from 9.94 g of CoSO4 and 250 ml of water?

4. How many grams of AgF are needed to make 500-ml of a 1.5 M solution?

Auto-ionization/Self-ionization

Refers to the breakdown of H2O to ions.

H2O H+ + OH-

Chcts:

1. reversible

2. neutral state = 50/50 ratio

3. Kw ionization product constant of water.

Other than Water

If the concentration of H+ is greater than OH-, then the solution is acidic.

[H+] > [OH-] acidic solution

If the concentration of H+ is less than OH-, then the solution is basic

[H+] < [OH-] basic solution

The pH Scale

A. pH Scale: a scale relative to the [H+] to [OH-].

1. Scale:

14 ------------------- 7 ---------------------- 0

Basic Neutral Acidic

2. pH = -log [H+]

3. pOH = -log [OH-]

pH Problems

1. [H+] : 6.5 x 10-10 = pH of ___________

2. [H+] : 6.8 x 10-10 = [OH-] ___________

3. pH = 4.697 is a [H+] = _______________

4. What is the pOH of problem #3. _______

5. pOH = 8.992, what is the pH : _________

6. [H+] is 3.7 x 10-6, what is the pH: ______

7. What is the [OH-] in #6

4. Chstc:

a. pH + pOH = 14

b. Kw = [H+] x [OH-] (add exponents)

c. [H+] = inv log or antilog -pH

d. [OH-] = inv log or antilog -pOH

5. Indicators: substances that change color in the present of an acid or base.

Acid/Base Strengths

A. Keq: Equilibrium rate constant for a reaction. Describes a point of equilibrium for a reaction.

1. Depends on solubility. See table.

a. Greater solubility = stronger solution

b. Keq = [product(s)] / [reactant(s)]

HCl + H2O H3O+ + Cl-

Ka : Acid Dissociation Constant

Ka = [Product (s)] / [Reactant(s)]

4HCl + O2 2Cl2 + 2H2O

1. Chcts:

a. concentrations raise to the power of the coefficient in a balanced equation.

b. Smaller the Ka the weaker the acid

c. Large Ka means large dissociation.

Kb : Base Dissociation Constant

Kb = [Product(s)] / [Reactant(s) ]

KOH K+ + OH-

1. Chstc:

a. Smaller Kb = weaker bases

b. Large Kb means large dissociation.

Table 19.5 and 19.6 pages 557 and 558.

Ka and Kb Sampler

Calculate the Ka from pH:

1. Write the balanced equation.

2. Write the Ka or Kb expression.

3. Use the given pH to find [H+].

4. Distribute the [ ] & subtract from the initial [ ].

The pH of a 0.2 M HC2H3O2 is 2.72. What is the Ka for acetic acid?

Practice Problems

1. Given a 0.1 M solution of sulfurous acid with a pH of 1.48, calculate the Ka.

2.A 0.2 M solution of benzoic acid, C6H5COOH has a pH of 2.45. What is the Ka ?

3.A basic solution with a pH of 12.5 has a concentration of 0.25 M BOH. What is the Kb?

Calculating pH from Ka or Kb

1. Write a balanced equation.

2. Write the Ka or Kb expression.

3. Use the equation diagram to define ‘x’.

4. Using the given Ka (Kb) , insert ‘x’ for [H+] and [A-].

5. Eliminate ‘x’ in the denominator.

6. Solve for ‘x’

7. Calculate pH or pOH

Calculate pH from Ka/Kb

1. A given 0.15 M solution of nitrous acid, HNO2, has a Ka = 3.45 x 10-5. What is the pH?

2. A solution of 0.2 M, CsOH , has a Kb = 1.25 x 10-8. What is the pH ?

3. A solution is prepared by adding 56.3 g of HCl and 62.1 g of NaOH to enough water to make 250 ml. Determine the pH of the solution?

TitrationTitration is a process by which a solution of

known concentration is used to determine the concentration of an unknown solution.

Indicators: Chemicals that are effected by pH and used to determine the equivalent point.

Equivalent Point: point of neutralization. The pH at this point depends on the strength of the acids/base involved.

Calculating

Process to determine the [ ] of an unknown solution from a known solution.

Setup ?

pH meter

Indicators: changes color @ end-point

End-point: indicates pH range via indicator

Equivalent point (ovhd) mole H+= moles OH-

Buffer :reduce change in pH. Hold pH steady

Buffer Capacity: amount of acid/base that can be absorbed before change in pH

increase [ ] = increase in capacity

Buffers contain common ions or weak acids and their conjugate base.

What is the buffer for the reaction:

HCN H+ + CN-

Ans: any salt that contained CN- that will reverse the reaction thereby reducing H+

Calculations with titration

Find the [ ] of an unknown by titration

It takes 26.4 ml of 0.25 M HBr solution to neutralize 30 ml of CsOH. Find [ ]

1.Write a balanced equation

2.Convert

ml L given [ ] mole ratio [?]

ans: 0.22 M CsOH

What is the [ ] of nitric acid if 43.33 ml of a 0.1 M KOH is neutralize 20 ml of HNO3 ?

1.Balance the equation.

2.Convert

ml L given [ ] mole ratio [ ]

3. Use [ ] to calculate pH.

Textbook: p621 #32-33 ; p631 #72-80

p 632 #93-96

Sampler

1. What is the concentration of a household ammonia solution if 4909 ml 0.59 M HCl is required to neutralize 25 ml solution?

2. In a titration, 33.21 ml 0.3020 M rubifium hydroxide solution is required to exactly neutralize 20 ml of HF acid solution. What is the molarity of HF ?