1

Feb 28­4:40 PM

H

O

OHO

O

sCl H

Acids and Bases

HH

H

N

Na O H

Feb 23­9:31 AM

Properties of Acids­1. Taste sour2. Conduct electrical current3. Liberate H2 gas when reacted with a metal.4. Cause certain dyes to change color (Litmus, an indicator, turns from blue to red.)5. Have a pH less than 7 (0­7)

Ex: Fruits with citric acidVinegar with acetic acidRain water with sulfuric acidSoda with carbonic and phosphoric acid

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Feb 23­9:32 AM

Properties of a Base (sometimes called alkaline) ­

1. Taste bitter2. Conduct electrical current3. Feel Slippery4. Cause certain dyes to change color (Litmus, an indicator, turns from red to blue)5. Have pH more that 7 (7­14)

Ex: Drano contains sodium hydroxideCleaners contain ammoniaMilk of magnesia contains magnesium hydroxide

Feb 20­11:25 AM

Acids and BasesArrehenius’ Acid Definition: Substances that will dissolve in water to give a solution that will: give H+ ions

Strong Acid: HCl(aq)→

Weak Acid: HC2H3O2 (aq)

[H3O+ hydronium]

3

Feb 20­11:34 AM

Arrehenius’ Base Definition: Things that will dissolve in water to give a solution that will: give OH­

Examples:

Strong Base: NaOH(s)

Weak Base: K2O(s)

Apr 20­1:03 PM

Both Acids and Bases Lose their Properties when reacted together­NeutralizationWhy?

HA + MOH HOH + MA

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Apr 20­1:03 PM

Is there a problem with the Arrhenius' Definition?

1. Only aqueous solutions

2. What about ammonia?

3. H+ is not stable in water solutions.

4. What about amphoteric substances?

Feb 23­10:12 AM

Amphoteric­ substance whose solution can have both acidic & basic properties. Ex. H2O, HSO4

­, HPO4­2, H2PO4

­

↔ = equilibrium. The reaction does not go to completion;Reactants partially dissociate (break apart). How much/how quickly they dissociate depends on if they are weak or strong! Key: the stronger an acid/base is, the more it dissociates.

H2O + H2O Self­ionization of water

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Feb 20­11:38 AM

Brønsted ­ Lowry Definition:Acid: substance that can donate a proton (H+)

Base: substance that can accept a proton (H+)

Example:

HCl(l) + H2O(l)

HC2H3O2(l) + H2O(l)

Feb 20­11:38 AM

H3PO4(aq) + H2O(l)

NH3(aq) + H2O(l)

HCO3­(aq) + H2O(l)

HCl(aq) + H2O(l)

Conjugate Acid: what the base use to be plus a H+

Conjugate Base: what the acid use to be without the H+

Brønsted ­ Lowry Acid­Base Pairs:

Example:

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Feb 23­11:48 AM

Strength vs. Concentration

StrengthHow easy an A/B will break apart into its ions. (Things that won‛t break apart into ions are molecular compounds because they have covalent bonds.)

ConcentrationMolarity

Feb 23­11:48 AM

Examples of Strong…

Acids (The Big 6)HClHBrHIH2SO4

HNO3

HClO4

HCl(aq) →

Bases (Group 1 & 2)NaOHLiOHKOHBa(OH)2Mg(OH)2 Ca(OH)2

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Feb 23­11:48 AM

Examples of Weak… everything else.

HC2H3O2(aq) ↔

NH4OH(aq) ↔

Apr 20­1:24 PM

The more a substance ionizes, the better it will conduct an electrical current. Qualitatively, we use electricity to determine how well a substances dissociates in water.

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Apr 24­7:16 AM

STRONG ACID weak acid

STRONG BASE weak base

NaOH

HCl

NH3

NaHCO3

HC2H3O2HNO3 H2S

Ba(OH)2 NaClO

H2CO3

LiOH

HBr

KOH

HF

Sort the substances listed below into correct boxes

Al(OH)3

Apr 23­4:36 PM

You need your calculator!!!

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Apr 22­8:14 AM

Acidic Solutions [H+] [OH­]Basic Solutions [H+] [OH­]Neutral Solutions [H+] [OH­] H2O(l) ↔ H+

(aq) + OH­

(aq)

The pH Scale

P stands for power, H stands for [H+]. pH is a convenient way to measure the acidity or the amount of H+ ions present in a solution.

More H+ ions F pH

Less H+ ions F pH

Apr 23­4:23 PM

The pOH Scale

pOH measures the basicity or amount of OH­ ions present in a solution

***pH and pOH are dependent on both the concentration & strength.

*We will only consider strong acids & strong bases (completely dissociated).

1M HCl = 1M H+ ions

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Feb 28­7:52 PM

Review of logs (base 10).

A log is simply the power of 10 necessary to equal a given number

log 100 =

102 =

Apr 23­4:23 PM

Summary of equations to use

pH = ­log [H+] [H+] =10­pH

pH + pOH = 14 [H+][OH­] = 1 x 10­14

pOH = ­log [OH­] [OH­]=10­pOH

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Feb 23­10:18 AM

Ex. 1 What is the pH of a solution whose [H+] = 2.50 x 10­12 M?

Ex.2What is the pOH of this solution?

Ex 3Calculate the [OH­] for this solution. Is it Acidic or Basic?

Apr 20­1:27 PM

Quantitatively, the Equilibrium Constant, Keq, is used to determine how well a substance dissociates in water.

Definitions:→ a reaction that is complete (100% ionization)↔ a reaction that only takes place partially (< 100% ionization)[ ] the concentration of the compound (measured using molarity)Keq the equilibrium constant for an reaction at equilibrium

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Apr 20­1:27 PM

Keq the equilibrium constant for an reaction at equilibrium

For aA + bB ↔ cC + dD

*** The larger the K, the stronger the substance.

Apr 20­1:30 PM

6 Special K’sKc = Concentration (M) water is excludedKp = pressure (gases only­atm)Ksp = Solubility Product (slightly soluble solids) solids are excluded

Ka = Acids water is excludedKb = Bases water is excludedKw = water 1.0 X 10­14 M

Ex. Write the appropriate K expression for the following BCE’s. a) PbI2 (s) Pb+2(aq) + 2I­(aq)

b) H2O(l) H+(aq) + OH­

(aq)

c) SO2(g) + O2(g) SO3(g)

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Apr 17­3:24 PM

General Acid Equation

Ka =

General Base Equation

Kb =

HA + H2O --> A- +H3O+<--

A- + H2O --> HA + OH-<--

Apr 20­1:31 PM

4. Setup an ICE Table to determine the equilibrium concentration and return to step 3. Initial concentration Change in concentration Equilibrium concentration

4 Steps for solving equilibrium problems:

1. Write a BCE.

2. Write the equilibrium expression. (Solids or water in the liquid phase can be eliminated.)

3. If the equilibrium concentrations of everything are known...plug the numbers into the Keq expression...if not continue to step 4.

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Apr 22­8:16 AM

Ex. Aspirin is a weak acid. A chemist mixes 0.1000 moles of aspirin with water to make 1 L of solution. At equilibrium the H3O+ concentration was found to be 0.0057 M. What is the Ka for aspirin?

Apr 17­3:48 PM

Ex. The Ka of acetic acid is 1.75 x 10­5, find the equilibrium concentration of hydronium ions in a 1.00 M solution of acetic acid.

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Apr 29­8:28 AM

Ex. How many moles of sulfuric acid would you require to neutralize 0.50 mol of sodium hydroxide?

Apr 23­5:26 PM

Titrations­lab neutralization reactions used to determine pH, pOH, [H+],[OH­] or the molar mass of acids and bases.

Find Moles Required to Neutralize a Substance.1. Write a Balance Chemical Equation2. Take the moles of the substance that you have and calculate moles of the other substance that you need to neutralize it by using the mole ratio.

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Apr 29­8:30 AM

Tools & Calculations for Acid­Base Titrations

Burette­ graduated glass tube with a stopcock used to deliver a solution of known concentration.

Final Volume ­ Initial Volume = Volume Used

Standard Solution­ the solution of known concentration and known volume used.

Pipet­ a calibrated glass tube used to measure out exactly 0.5mL, 1mL, 10mL, 20mL, 25mL solutions

Solution of Unknown Concentration­ substance being titrated.

Erlenmeyer Flask­ contains substance being titrated

Indicator­ changes color to indicate the end of the titration. If a indicator is used to show the pH is 7 (neutral), at this point the moles of acid = moles of base. This is called the equivalence point and the end of our titration.

*** We will use Phenolphthalein.

Apr 29­8:32 AM

Step 1. Calculate moles of acid or base. Use the known molarity and volume of the standard solution to determine the # of moles of the standard solution reacted.

Step 2. Find the moles required to neutralize the substance. For 1:1 mole ratios, at the equivalence point the moles of acid will equal moles of base.

Step 3 Use the moles to determine pH, pOH, [H+],[OH­] or the molar mass.

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Feb 24­10:52 AM

Feb 28­4:39 PM

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Feb 24­9:04 AM

Salts­ Ionic compounds w/o H+ ions or OH­ ions

Hydrolysis­ Reaction with water (opposite of neutralization)

***May be acidic or basic or neutral

Definitions

Feb 24­9:04 AM

4 Situations­ Salts made from…

1. The cation of a strong base & the anion of a weak acid.

Ex. NaC2H3O2 + H2O NaOH + HC2H3O2

Ionic strong base weak acid

Will this salt be acidic, basic or neutral? Show with a net ionic equation.

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Feb 24­9:14 AM

2. The cation of a weak base & the anion of a strong acid.

Ex. AlCl3 + 3H2O Al(OH)3 + 3HCl

3. The cation of a strong base & the anion of a strong acid

Ex. NaCl + H2O HCl + NaOH

Feb 24­9:16 AM

4. The cation of a weak base & the anion of a weak acid**Compare Ka of cation to Kb of anion

Ka > Kb = acidicKb > Ka = basicKa = Kb = neutral