The Acid Test

Acids, Bases and pH

Range of pH scale

The pH scale ranges from 0 to 14.

There are no units of measure for pH *

What do the numbers mean?

A pH of 7 is neutral Pure water has a pH

of 7*

How about below 7? Anything below 7 is acidic 0 is the most acidic and

6.99999 is the least acidic The further something is from

7 the more acidic it is*

How about above 7? higher than 7 is

basic/alkaline So 7.000001 is a weak

base and 14 is the most basic (or alkaline)*

pH Range

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14

Neutral[H+]>[OH-] [H+] = [OH-] [OH-]>[H+]

Acidic Basic

The pH Scale pH

measures acidity and alkalinity (how basic) a liquid is*

Ionization of Water

Occasionally, in water, a H+ is transferred between H2O molecules

. . . . . . . .H:O: + :O:H H:O:H + + :O:H-

. . . . . . . . H H H

water molecules hydronium hydroxide ion (+) ion (-)

Measuring pH

Litmus paper, pH paper, and pH meters*

Litmus paper Litmus paper cannot

tell you the exact pH of a substance.

It can only tell you if it is an acid or a base

Blue litmus turns pink in the presence of an acid

Red litmus turns blue in the presence of a base*

pH paper pH paper can tell you

approximate pH values.

By placing one end of the pH paper in the solution it will turn a color which can be matched to the color code key. *

Indicators •Indicators:

•Weak organic acids and bases whose colors differ from the colors of their conjugate acids or bases.

•The color is best viewed from above against a white background

Table of Indicators•      •Acid / Base Indicators•Indicator •Lower Color •pH Range •Upper Color•methyl violet •yellow-green •0.0 - 2.5 •violet

•methyl orange •red •2.5 - 4.4 •yellow

•congo red •blue •3.0 - 5.0 •red

•bromocresol green •yellow •4.5 - 5.5 •blue

•methyl red •red •4.8 - 6.0 •yellow

•bromocresol purple •yellow-green •5.4 - 6.8 •violet

•bromothymol blue •yellow •6.0 - 7.6 •blue

•phenol red •yellow •6.4 - 8.2 •red-violet

•cresol red •yellow •7.1 - 8.8 •violet

•phenolphthalein •colorless •8.3 - 10.0 •dark pink•Phenolphthalein is a common indicator to use in neutralization titrations. The solution is considered neutral when the solution holds a very faint pink color for half a minute or more.

•alizarin yellow R •yellow •9.9 - 11.8 •dark orange

pH Meter The most precise and

usually more accurate way to measure pH is using a pH meter which directly measures the amount of [H3O+] in the solution

Uses an electrode which specifically measures the pH of the solution.

This is a larger model. Some are small enough to be hand-held.*

What is an Acid? Sour Taste (We never taste chemicals in lab) release hydrogen (H+) React with metals to release H2

React with a base to produce water and a salt (neutralization reaction)

Some that completely dissociate conduct current (electrolytes)

Turns blue litmus paper red*

Naming Acids

Binary (begin with hydro-) Oxyacids do not have hydro- *

Naming Binary Acids Binary acids contain hydrogen and one

other element Binary acids begin with hydro- Binary acids end with –ic*

Test your naming skills of these acids HF HCl HBr HI H2S

Hydrofluoric acid Hydrochloric acid Hydrobromic acid Hydroiodic acid Hydrosulfuric acid*

Oxyacid An acid that is a compound of hydrogen,

oxygen and a third element (usually a nonmetal)

These do not contain hydro- Can end in either –ic or –ous*

Name these Oxyacids CH3COOH H2CO3

HIO3

HClO HClO2

HClO3

HClO4

HNO2

Acetic acid Carbonic acid Iodic acid Hypochlorous acid Chlorous acid Chloric acid Perchloric acid Nitrous acid*

Name these oxyacids HNO3

H3PO4

H3PO3

H2SO4

H2SO3

Nitric acid Phosphoric acid Phosphorous acid Sulfuric acid Sulfurous acid*

Common Industrial Acids Sulfuric Nitric Phosphoric Hydrochloric Acetic *

Sulfuric Most commonly produced acid worldwide Petroleum refining Metallurgy Fertilizer manufacturing Production of metal, paper, paint, dyes,

detergents Automobile batteries*

Sulfuric Acid Can be used to dehydrate (water removing) Sugar can be dehydrated by this acid Has the same effect on organic tissue

causing severe burns *

Nitric Acid Volatile and unstable in its pure form Rarely used in its pure form Stains yellow and burns skin Used in the making of explosives rubber,

plastics, dyes and pharmaceuticals *

Phosphoric Acid Manufacture of fertilizer and animal feed Flavoring agent in dilute form Cleaning agent for dairy equipment Manufacture of detergents and ceramics*

Hydrochloric acid Produced in your stomach to aid in

digestion Used to remove surface impurities of

metals (iron and steel) Cleaning agent in food industry Also known as muriatic acid in a dilute

form Adjust the pH of Swimming pools*

Different Definitions of Acids and Bases

ArrheniusBronsted-LowryLewis*

Arrhenius Acids and Bases Arrhenius acid is a chemical compound

that increased the concentration of H+ in an aqueous solution

Arrhenius base is a chemical that increases the concentration of OH- ions in an aqueous solution *

Characteristics of Acids and Bases Acids Taste sour Donate a H+

pH less than 7 Turn litmus paper red Turn bromothymol

blue to yellow Turn phenolphthalein

colorless Neutralize bases

Bases Taste bitter Usually ends in -OH pH greater than 7 Turn litmus paper

blue Turn bromothymol

blue to blue Turn phenolphthalein

pink Feel slippery to touch Neutralize acids*

Learning Check AB1Describe the solution in each of the following as: 1) acid 2) base or 3)neutral.A. ___soda

B. ___soapC. ___coffeeD. ___ wineE. ___ water

F. ___ grapefruit*

Solution AB1Describe each solution as: 1) acid 2) base or 3) neutral.A. _1_ soda

B. _2_ soapC. _1_ coffeeD. _1_ wineE. _3_ water

F. _1_ grapefruit*

Learning Check AB2Identify each as characteristic of an A) acid or B) base____ 1. Sour taste ____ 2. Produces OH- in aqueous solutions

____ 3. Chalky taste____ 4. Is an electrolyte____ 5. Produces H+ in aqueous solutions*

Solution AB2 Identify each as a characteristic of an A) acid or B) base_A_ 1. Sour taste

_B_ 2. Produces OH- in aqueous solutions

_B_ 3. Chalky taste

A, B 4. Is an electrolyte

_A_ 5. Produces H+ in aqueous solutions*

Arrhenius Acids and Bases Acids produce H+ in aqueous solutions

waterHCl H+(aq) + Cl- (aq)

Bases produce OH- in aqueous solutions

water

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

Learning Check AB3

Give the names of the following A. HBr (aq) 1. bromic acid

2. bromous acid 3. hydrobromic acid

B. H2CO3 1. carbonic acid

2. hydrocarbonic acid

3. carbonous acid*

Solution AB3A. HBr 3. hydrobromic acidThe name of a nonoxy acid begins with the prefix hydro- and ends with -ic acid. In a nonoxy acid, the negative anion end in -ide.

B. H2CO3 1. carbonic acidThe name of an oxyacid is named with the stem of the anion (carbonate) changed to -ic acid *

Some Common BasesNaOH sodium hydroxide

KOH potassium hydroxide

Ba(OH)2 ________________________

Mg(OH)2 ________________________ Al(OH)3

aluminum hydroxide*

Learning Check AB4Match the formulas with the names:

A. ___ HNO2 1) hydrochloric acid

B. ___ Ca(OH)2 2) sulfuric acid

C. ___ H2SO4 3) sodium hydroxide

D. ___ HCl 4) nitrous acid

E. ___ NaOH 5) calcium hydroxide*

Solution AB4Match the formulas with the names:

A. _4__ HNO2 1) hydrochloric acid

B. _5__ Ca(OH)2 2) sulfuric acid

C. _2__ H2SO4 3) sodium hydroxide

D. _1__ HCl 4) nitrous acid

E. _3__ NaOH 5) calcium hydroxide*

Learning Check AB5

Acid, Base Nameor Salt

CaCl2 ______ _________________

KOH ______ _________________

Ba(OH)2 ______ _________________

HBr ______ _________________

H2SO4* ______ __________________

Solution AB5Acid, Base Nameor Salt

CaCl2 salt calcium chloride

KOH base potassiuim hydroxide

Ba(OH)2 base barium hydroxide

HBr acid hydrobromic acid

H2SO4 acid sulfuric acid*

Bronsted-Lowry AcidsAcids are hydrogen ion (H+) donorsBases are hydrogen ion (H+) acceptors

HCl + H2O H3O+ + Cl-

donor acceptor + -

+ +

Strengths of Acids and BasesStrong acids completely ionize (100%) in aqueous solutions

HCl + H2O H3O+ + Cl- (100 % ions)Strong bases completely (100%) dissociate into ions in aqueous solutions.

NaOH Na+ (aq) + OH-(aq) (100 % ions)*

NH3, A Bronsted-Lowry BaseWhen NH3 reacts with water, most of the reactants remain dissolved as molecules, but a few NH3 reacts with water to form NH4

+ and hydroxide ion.

NH3 + H2O NH4+(aq) + OH- (aq)

acceptor donor

+ +

Strong and Weak Acids and Bases

Strong acids

HCl, HNO3 , H2SO4

Most other acids are weak.

Strong bases

NaOH, KOH, and Ca(OH)2

Most other bases are weak.*

Learning Check SW1Identify each of the following as a 1) strong acid or base 2) weak acid 3) weak baseA. ___ HCl (aq)B. ___ NH3(aq)

C. ___ NaOH (aq)D. ___ H2CO3 (aq)

Solution SW1Identify each of the following as a 1) strong acid or base 2) weak acid 3) weak baseA. _1__ HCl (aq)B. _3__ NH3(aq)

C. _1__ NaOH (aq)D. _2__ H2CO3 (aq)*

Antacids

Used to neutralize stomach acid (HCl)Many contain one or more weak bases

Alka-Seltzer: NaHCO3, citric acid, and aspirin

Di-gel: CaCO3 and Mg(OH)2

Gelusil: Al(OH)3 and Mg(OH)2

Maalox: Al(OH)3 and Mg(OH)2

Mylanta: Al(OH)3 and Mg(OH)2*

More Antacids

Milk of Magnesia: Mg(OH)2

Rolaids: AlNa(OH)2CO3

aluminum sodium dihydroxy carbonate

Tums: CaCO3

Tempo: CaCO3, Al(OH)3, Mg(OH)2*

Types of Acids

Monoprotic DiproticPolyprotic *

Monoprotic An acid that donates one proton HCl CH3COOH (the H on the end is donated)*

Diprotic Donates two protons Ex. H2SO4*

Polyprotic Donates more than two hydrogen atoms Ex. H3PO4*

Lewis Acids and Bases Lewis Acid: atom, ion, or molecule that

accepts an electron pair to form a covalent bond

Lewis Base: atom, ion, or molecule that donates an electron pair to form a covalent bond *

Concentrations In lab, our concentrations are marked like

this 0.01 M M = concentration of moles per liter The bigger the number the higher the

concentration. Which one is a stronger concentration?

0.001 M or 0.1M? *

Dilutions Add water Volume increases. New concentration is less than initial*

Concentration of A Diluted Solution

A 25 mL sample of a 6.0 M KOH is diluted by adding 75 mL of water. Calculate the new concentration of the KOH solution.

Moles KOH = 0.025 L x 6.0 moles = 0.15 moles1 L

New volume = 25 mL + 75 mL = 100. mL = 0.100 LNew molarity = 0.15 moles = 1.5 M* 0.100 L

Learning Check SW 2A 125 mL sample of a 3.0 M HCl is diluted by adding 250 mL of water. The new concentration of the HCl solution is1) 8.0 M2) 1.5 M3) 1.0 M*

Solution SW 23) 1.0 M

moles HCl = 0.1250 L x 3.0 moles = 0.375 mole 1 L

new M = 0.375 mole 1.0 M HCl 0.3750 L(new volume)*

Learning Check SW 3A 50.0 mL sample of 15% sucrose solution is diluted by adding 200. mL of water. The new concentration of the sucrose solution is1) 3.0 %2) 7.5 %3) 10. %*

Learning Check SW 3A 50.0 mL sample of 15% sucrose solution is diluted by adding 200. mL of water. The new concentration of the sucrose solution is1) 3.0 %g sucrose = 50.0 mL x 15 g sucrose = 7.5 g

100 mL new % = 7.5 g sucrose = 3.0 % sucrose

250 mL (new volume) *

Neutralization ReactionsWhen acid and bases with equal amounts of hydrogen ion H+ and hydroxide ions OH- are mixed, the resulting solution is neutral.

NaOH (aq) + HCl(aq) NaCl + H2Obase acid salt water

Ca(OH)2 + 2 HCl CaCl2 + 2H2Obase acid salt water*

Neutralization H3O+ and OH- combine to produce water

H3O+ + OH- 2 H2O from acid from base neutral

Net ionic equation:

H+ + OH- H2O*

Ionic Equations for Neutralization

Write strong acids, bases, and salt as ionsH+ + Cl- + Na+ + OH- Na+ + Cl- + H2O

Cross out matched ionsH+ + Cl- + Na+ + OH- Na+ + Cl- + H2O

Write a net ionic reactionH+ + OH- H2O*

Balancing Neutralization EquationsWrite the equation for the neutralization between magnesium hydroxide and nitric acid.1. Write the formulas of the acid and base

Mg(OH)2 + HNO3

2. Balance to give equal OH- and H+

Mg(OH)2 + 2 HNO3*

3. Write the products:

Mg(OH)2 + 2HNO3 Mg(NO3)2 + H2Osalt water

(metal and nonmetal)

4. Balance products

Mg(OH)2 + 2 HNO3 Mg(NO3)2 + 2 H2O*

Learning Check N2Select the correct group of coefficients for the following neutralization equations

A. __ HCl + __ Al(OH)3 __AlCl3 + __ H2O

1) 1, 3, 3, 1 2) 3, 1, 1, 1 3) 3, 1, 1 3

B.__ Ba(OH)2 + __H3PO4 __Ba3(PO4)2 + __ H2O

1) 3, 2, 2, 2 2) 3, 3, 1, 6 3) 2, 3, 1, 6

Solution N2

A. 3HCl + 1Al(OH)3 1AlCl3 + 3H2O

B. 3Ba(OH)2 + 2H3PO4 1Ba3(PO4)2 + 6H2O*

Learning Check N3

Write a balanced equation and calculate the mL of 2.00 M H2SO4 required to neutralize 50.0 mL of 1.00 M KOH?

___H2SO4 + ___KOH ___K2SO4 + H2O

1) 12.5 mL 2) 50.0 mL 3) 200. mL*

Solution N3

How many mL of 2.00 M H2SO4 are required to neutralize 50.0 mL of 1.00 M KOH?

H2SO4 + 2KOH K2SO4 + 2H2O

0.0500 L x 1.00 mole KOH x 1 mole H2SO4 x

1 L 2 mole KOH

1 L x 1000 mL = 12.5 mL

2 mole KOH 1 L *

Learning Check N4A 25 mL sample of phosphoric acid is neutralized by 40. mL of 1.5 M NaOH. What is the molarity of the phosphoric acid solution?

3NaOH + H3PO4 Na3PO4 + 3H2O

1) 0.45 M 2) 0.80 M 3) 7.2 M*

Solution S4

0.040 L x 1.5 mole NaOH x 1 mole H3PO4

1 L 3 mole NaOH

x 1 = 0.80 mol/L = 0.80 M*

0.025 L***

Logarithms and pH Calculations

Scientific Notation ReviewLog Review (or Introduction)pH formulaspH calculations

Pure Water is NeutralPure water contains small, but equal amounts of ions: H3O+ and OH-

H2O + H2O H3O+ + OH-

hydronium hydroxide ion ion

1 x 10-7 M 1 x 10-7 M*H3O+ OH-

Acids Increase H+

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

(aq)

More [H3O+] than water > 1 x 10-7M

As H3O+ increases, OH- decreases

[H3O+] > [OH-]*H3O+

OH-

BasesIncrease the hydroxide ions (OH-) H2O

NaOH (s) Na+(aq) + OH- (aq)More [OH-] than water, [OH-] > 1 x 10-7M

When OH- increases, H3O+ decreases

[OH] > [H3O+]*

H3O+OH-

Using logarithms and scientific notation Logarithms also called logs are exponents Log of (1 x 10-14) = -14 Log of 0.001 = 1 x 10-3 = -3 You can also take the –log which would be

–log 0.00001 = -log 1 x 10-5 = -(-5) = 5*

Using the Calculator1.0 x 10 -14

4.0 x 10-5

Enter 1.0 EE +/- 14 4.0 EE +/- 5

= 2.5 x 10 –10*

pH Indicates the acidity [H3O+] of the solution

pH = - log [H3O+]

From the French pouvoir hydrogene (“hydrogen power” or power of hydrogen)*

In the expression for [H3O+]

1 x 10-exponent

the exponent = pH

[H3O+] = 1 x 10-pH M*

pH

Calculating pH pH is found by using the formulapH = - log [H3O+]

pH + pOH = 14 pOH = -log [OH-]*

pH on the Calculator[H3O+] is 4.5 x 10-6 M

pH = 4.5 x EXP(or EE) 6+/- LOG +/-

= 5.35*

Applying logs to pH calculations If you have an acid with concentration of

0.01M what is the pH? Answer: 0.01 = 1x10-2 pH = -log (1x10-2) = -(-2) = 2*

Some [H3O+] and pH

[H3O+] pH

1 x 10-5 M 5

1 x 10-9 M 9

1 x 10-11 M 11*

Applying concentration to base pH If you have a BASE with concentration of

0.0001 M what is the pH? 0.0001 = 1 x 10-4 pOH = -log (1x10-4) =-(-4) = 4 but this is

pOH, so then we have to say pH + pOH = 14. So pH + 4 = 14; thus, pH = 10.*

Learning Check pH4 A. The [H3O+] of tomato juice is 1 x 10-4 M.

What is the pH of the solution?1) - 4 2) 4 3) 8

B. The [OH-] of an ammonia solution is

1 x 10-3 M. What is the pH of the solution?

1) 3 2) 11 3) -11*

Solution pH4A. pH = - log [ 1 x 10-4] = -(- 4) = 4

B. [H3O+] = 1 x 10-11

pH = - log [ 1 x 10- 11] = -(- 11) = 11*

Learning Check pH5The pH of a soap is 10. What is the [H3O+] of the soap solution?

1) 1 x 10 - 4 M

2) 1 x 1010 M

3) 1 x 10 - 10 M *

Solution pH5The pH of a soap is 10. What is the [H3O+] of the

soap solution?

[H3O+] = 1 x 10-pH M = 1 x 10-10 M*

Learning Check pH6A soap solution has a [H3O+] = 2 x 10-8 M. What is the pH of the solution?

1) 8

2) 7.7

3) 6*

Solution pH6A soap solution has a [H3O+] = 2.0 x 10-8 M. What is the pH of the solution?

B) 2.0 EE 8 +/- LOG +/- = 7.7*

Learning Check pH7Identify each solution as1. acidic 2. basic 3. neutral

A. _____ HCl with a pH = 1.5

B. _____ Pancreatic fluid [H+] = 1 x 10-8 M

C. _____ Sprite soft drink pH = 3.0

D. _____ pH = 7.0

E. _____ [OH- ] = 3 x 10-10 M

F. _____ [H+ ] = 5 x 10-12*

Solution pH7Identify each solution as1. acidic 2. basic 3. neutral

A. _1__ HCl with a pH = 1.5

B. _2__ Pancreatic fluid [H+] = 1 x 10-8 M

C. _1__ Sprite soft drink pH = 3.0

D. _3__ pH = 7.0

E. _1__ [OH-] = 3 x 10-10 M

F. _2__ [H+] = 5 x 10-12*

Acid RainUnpolluted rain has a pH of 5.6

Rain with a pH below 5.6 is “acid rain“

CO2 in the air forms carbonic acid

CO2 + H2O H2CO3

Adds to H+ of rain

H2CO3 H+ (aq) + HCO3-(aq)*

Formation of acid rain:1. Emission of sulfur and nitrogen oxides from the burning of fuels expecially coal with high S content,

power stations, oil refineries, vehicles as well as bacterial decomposition, and lighting hitting N2

SO2 26 million tons in 1980NO and NO2 22 million tons in 1980Mt. St Helens (1980) 400,000 tons SO2

Acid RainFormation of acid rain:1. Emission of sulfur and nitrogen oxides from the

burning of fuels especially coal with high S content, power stations, oil refineries, vehicles as well as bacterial decomposition, and lighting hitting N2

SO2 26 million tons in 1980NO and NO2 22 million tons in 1980Mt. St Helens (1980) 400,000 tons SO2*

Acid Rain 2. Reactions in the atmosphere form SO3

2SO2 + O2 2 SO3*

Acid Rain 3. Reactions with atmosphere water form

acidsSO3 + H2O H2SO4 sulfuric acid

NO + H2O HNO2 nitrous acid

HNO2 + H2O HNO3 nitric acid*

Acid Rain4. Effects of Acid Rain

Decline in fish populations in rivers and lasts due to toxic effect of Al leached from soil by acid rain

Extensive fish kills in spring from runoff due to accumulation of large amounts of acid on the snow

Dissolves minerals Mg, Ca, and K from the soil and waxy coatings that protect leaves from bacteria

Corrodes metals, textiles, paper and leather*

Sources of Acid Rain

Power stationsOil refineries

Coal with high S content

Car and truck emissions

Bacterial decomposition, and lighting hitting

N2*

Titration

Acids and BasesQuantitative Analysis*

Acid/Base Titration Titration is an analytical method in

which a standard solution is used to determine the concentration of another solution.

Any solution for which the concentration is precisely known is called a standard solution. *

Titration

                        

Titration Movie

Before EndpointAt the Endpoint—Color persists for 30 s after swirling

Over Titrated—missed endpoint—Start over!

Titrations (cont.) An acid/base titration uses the fact that one can be

"neutralized" with the other. In this neutralization reaction, the acid and base will combine to produce a salt plus water. When done correctly, the resulting solution will be "neutral" - neither acid nor base. In a titration, this is known as the end point. The change in pH of the solution can be monitored using an indicator or pH meter. It is extremely important that the exact amounts of each solution used be known at the end point. *

Titration Curve

This graph represents the titration of 10 ml of 0.1M HCl with 0.1M NaOH. The end point is characterized by a rapid change in pH with very little base added. *

Titration Problem Example: If 20 cm3 of a 0.3 M solution of NaOH is required to neutralize 30.0 cm3 of a sulfuric acid solution, what is the molarity of the acid solution? Solution Steps:

1.Write a balanced equation: 2NaOH + H2SO4      Na2SO4 + 2H2O  

2.Determine the number of moles of the standard NaOH solution used:  

                                                                                      

 

3.Use the mole ratio from the balanced equationto convert moles of NaOH to moles of H2SO4:  

                                                                                                                       

 

4.Use the volume of acid solution used to determine the molarity of the acid solution:  

                                                                                                                                                              

 Notice that the   1dm3/1000cm

3   and the   1000cm3/1dm3   will offset each other. You may shorten the problem by skipping these

conversions.

THE END