acids and bases. properties of acids a acids taste sour acids effect indicators blue litmus turns...

Acids and Bases

Properties of AcidsProperties of Acids Acids taste sour Acids effect indicators

Blue litmus turns red Methyl orange turns red

Acids have a pH lower than 7 Acids are proton (hydrogen ion, H+) donors Acids react with active metals, produce H2

Ex: Reactions lab

Acids react with carbonates to produce CO2

Acids neutralize bases

Blue litmus paper turns red in contact with an acid.

Acid Base

Acids Neutralize Bases

Effects of Acid Rain on Marble(calcium carbonate)

George Washington: BEFORE

George Washington: AFTER

Acids React with Active Metals

Acids react with active metals to form salts and hydrogen gas.

Mg + 2HCl MgCl2 + H2(g)

Magnesium

•Acids Taste Sour.

Dilutions of Acids

ALWAYS ADD ACID TO WATER

This reduces the chance that it will blow up in your face due to the heat of reaction

making steam rapidly. The denser acid will sink and disperse

more evenly.

Binary Acids

• An acid that contains hydrogen

and one other element.

Naming Binary Acids

The proper method to use when naming binary acids is to begin with the hydro- prefix, use the

root of the nonmetal, and add the –ic suffix.

Oxyacids

• An oxyacid is a compound of hydrogen, oxygen, and a third element, usually a nonmetal.

Method for Naming Oxyacids• If the acid consists of one more oxygen than the

polyatomic ion with the -ate suffix, use the per- prefix, the root of the polyatomic ion and the –ic suffix.– Example HClO4 = perchloric acid

• If the acid consists of a polyatomic ion with the -ate suffix, use the root of the polyatomic ion and add –ic.– Example HClO3 = chloric acid

• If the acid consists of hydrogen and a polyatomic ion with the -ite suffix, use the root of the polyatomic ion and add –ous.– Example HClO2 = chlorous acid

• If an acid consists of one less oxygen than the polyatomic ion ending in –ite, use the hypo prefix, the root of the polyatomic ion and the –ous suffix.– Example HClO = hypochlorouc acid

Naming Acids

_________ ide (chloride, Cl1-)

_________ite (chlorite, ClO2

-) (hypochlorite, ClO-)

_________ ate (chlorate, ClO3

-) (perchlorate, ClO4

-)

Hydro____ ic acid (hydrochloric acid, HCl)

_________ic acid (chloric acid, HClO3)

(perchloric acid, HClO4)

______ous acid (chlorous acid, HClO2)

(hypochlorous acid, HClO)

Anion Acid

add H+

add H+

add H+

ions

ions

ions

Name the Acid

Acids you must know:Acids you must know:

Strong Acids

Weak Acids

Hydrochloric acid, HCl

Nitric acid, HNO3

Sulfuric acid, H2SO4

Phosphoric acid, H3PO4

Acetic acid, CH3COOH

Sulfuric Acid

Highest volume production of any chemical in the U.S.

Used in the production of paper

Used in production of fertilizers

Used in petroleum refining

Nitric AcidNitric Acid

• Used in the production of Used in the production of fertilizers fertilizers

• Used in the production of Used in the production of explosives explosives

• Nitric acid is a volatile acid Nitric acid is a volatile acid – its reactive components – its reactive components evaporate easily evaporate easily

• Stains proteins (including Stains proteins (including skin!)skin!)

Hydrochloric Acid

• Used in the pickling of steel

• Used to purify magnesium from sea water

• Part of gastric juice, it aids in the digestion of protein

• Sold commercially as “Muriatic acid”

• Muriatic Acid (HCl)– Sold commercially

– Useful for cleaning concrete– Buyer beware

Phosphoric Acid

o A flavoring agent in sodas o Used in the manufacture of

detergents o Used in the manufacture of

fertilizers o Not a common laboratory

reagent

Acetic AcidUsed in the

manufacture of plastics Used in making

pharmaceuticals Acetic acid is the acid

present in vinegar

Strength of Acids

Acids are proton (hydrogen ion, H+) donors

Strong acids are assumed to be 100% ionized in solution (good proton donors).

Weak acids are usually less than 5% ionized in solution (poor proton donors).

Acids are Proton Donors

Monoprotic acidsDiprotic acids Triprotic acids

HCl

HC2H3O2

HNO3

H2SO4

H2CO3

H3PO4

Comparison of a Monoprotic Acid to a Diprotic Acid

Strong acids such as HCl ionize almost completrly in solution, forming

hydronium ions, H3O+

H2O + HCl H3O+ + Cl-

Proton donor

Proton acceptor

Weak acids favor reverse reactions and enter chemical

equilibrium before many hydronium ions, H3O+ form.

Organic Acids

Organic acids all contain the “carboxyl” group, sometimes several of them.

The carboxyl group is a poor proton donor, so ALL organic acids are weak acids.

Examples of Organic Acids Citric acid in citrus fruit Malic acid in sour

apples Deoxyribonucleic acid,

DNA Amino acids, the

building blocks of protein

Lactic acid in sour milk and sore muscles

Butyric acid in rancid butter

The pH scale is used to measure the

strength of an acid or base. A pH of less than 7 indicates an acid. The lower the pH, the stronger the

acid.

pH of Many Common Substances

Properties of Bases

Bases taste bitter Bases effect indicators

Red litmus turns blue Phenolphthalein turns purple

Bases have a pH greater than 7 Bases are proton (hydrogen ion,H+) acceptors Solutions of bases feel slippery

Bases neutralize acids

Bases Effect Indicators

Red litmus paper turns blue in contact with a base.

Phenolphthalein turns purple in a base.

Bases Have a Bases Have a pH of greater pH of greater

than 7.than 7.

The greater The greater the pH, the the pH, the

stronger the stronger the base.base.

Bases Feel Slippery and Taste Bitter

Bases Neutralize Acids

Milk of Magnesia contains magnesium hydroxide, Mg(OH)2, which neutralizes stomach acid, HCl.

2 HCl + Mg(OH)2

MgCl2 + 2 H2O

Examples of Bases

Sodium hydroxide (lye, Drano), NaOH

Potassium hydroxide, (Caustic Potash) KOH

Magnesium hydroxide, (milk of magnesia) Mg(OH)2

Calcium hydroxide (lime), Ca(OH)2

Different Acid-Base Definitions

Svante Arrhenius first defined acids to be proton (H+) donors and bases to be hydroxide ion

(OH-) donors in aqueous solution.

• The Arrhenius model of acids and bases is summarized by the following two reactions:

Bronsted-Lowry Definition of an Acid and Base

• Bronsted-Lowry Acid- a molecule or ion that is a proton donor.

• Bronsted-Lowry Base- a molecule or ion that is a proton acceptor.

Conjugate Acid-Base Pairs

• The conjugate base of a Bronsted acid is the species that remains after an acid has donated a proton.

• The conjugate acid of a Bronsted base is the species that is formed after the base has accepted the proton.

Bronsted Conjugate Acid-Base Pairs

The conjugate of a strong acid is a weak base.The conjugate of a strong base is a weak acid.

Example of a Weak Acid Hydrofluoric Acid, HF(Hydrogen atom- Red)(Fluorine atom- Blue)

Lewis Acids and Bases

Lewis Acid- a molecule or ion that is an electron pair acceptor.Lewis Base- a molecule or ion that is an electron pair donor.

Examples of How Bases FormBronsted Base = Proton AcceptorLewis Base = Electron Pair Donor

Bases Neutralize Acids

Acid + Base SaltSalt + Water

•Orange juice + milk bad taste

•Evergreen shrub + concrete dead bush

•Under a pine tree + fertilizer white powder

•HCl + NaOH NaCl + HOH

Products of Neutralization

HCl + NaOH

H2SO4 + Ca(OH)2

HNO3 + KOH

The products of neutralization are always a ______ and _______.

NaCl + H2O

CaSO4 + 2 H2O

KNO3 + H2O

salt water

Amphoteric• When a

substance acts like an acid

under one set of conditions and

as a base under another set of

conditions.

The pH scale is a way of The pH scale is a way of expressing the strength of expressing the strength of acids and bases. Instead of acids and bases. Instead of using very small numbers, using very small numbers, we just use the NEGATIVE we just use the NEGATIVE power of 10 on the Molarity power of 10 on the Molarity of the Hof the H++ (or OH (or OH--) ion.) ion.

Under 7 = acidUnder 7 = acid7 = neutral7 = neutral

Over 7 = base Over 7 = base

Calculating the pHpH = - log [H+]

(Remember that the [ ] mean Molarity)

Example: If [H+] = 1 X 10-10

pH = - log 1 X 10-10

pH = - (- 10)

pH = 10

Example: If [H+] = 1.8 X 10-5

pH = - log 1.8 X 10-5

pH = - (- 4.74)

pH = 4.74

8.2

pH:

A M

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Sca

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and

Bas

esCalculating [OH-] from pH

What is the [OH-] of a solution with pH = 4.95?

• First find [H3O+] • 4.95 = -log [H3O+]

• [H3O+] = 10-4.95 • [H3O+] = 1.12 x 10-5

• Now solve for [OH-]• [OH-] = 1 x 10-14 = 1.0 x 10-9

1.12 x 10-5

pH = -log[H3O+]

1 x 10-14 = [H3O+][OH-]

Try These!Try These!

Find the pH of these:Find the pH of these:

1)1) A 0.15 M solution of A 0.15 M solution of Hydrochloric acidHydrochloric acid

2) A 3.00 X 102) A 3.00 X 10-7-7 M M solution of Nitric solution of Nitric acidacid

pH = - log [HpH = - log [H++]]

pH = - log 0.15pH = - log 0.15

pH = - (- 0.82)pH = - (- 0.82)

pH = 0.82pH = 0.82

pH = - log 3 X 10pH = - log 3 X 10-7-7

pH = - (- 6.52)pH = - (- 6.52)

pH = 6.52pH = 6.52

pH calculations – Solving for H+pH calculations – Solving for H+pH calculations – Solving for H+pH calculations – Solving for H+

If the pH of Coke is 3.12, [HIf the pH of Coke is 3.12, [H++] = ???] = ???

Because pH = - log [HBecause pH = - log [H++] then] then

- pH = log [H- pH = log [H++]]

Take antilog (10Take antilog (10xx) of both) of both sides and get sides and get

1010-pH -pH == [H[H++]]

[H[H++] = 10] = 10-3.12-3.12 = 7.6 x 10 = 7.6 x 10-4-4 M M

*** to find antilog on your calculator, look for “Shift” *** to find antilog on your calculator, look for “Shift” or “2or “2nd nd function” and then the log buttonfunction” and then the log button

PROBLEM: You have 50.0 mL of 3.0 M PROBLEM: You have 50.0 mL of 3.0 M NaOH and you want 0.50 M NaOH. NaOH and you want 0.50 M NaOH. What do you do?What do you do?

PROBLEM: You have 50.0 mL of 3.0 M PROBLEM: You have 50.0 mL of 3.0 M NaOH and you want 0.50 M NaOH. NaOH and you want 0.50 M NaOH. What do you do?What do you do?

Add water to the 3.0 M solution to lower its Add water to the 3.0 M solution to lower its concentration to 0.50 M concentration to 0.50 M

Dilute the solution!Dilute the solution!

PROBLEM: You have 50.0 mL of 3.0 M NaOH PROBLEM: You have 50.0 mL of 3.0 M NaOH and you want 0.50 M NaOH. What do you and you want 0.50 M NaOH. What do you do?do?

PROBLEM: You have 50.0 mL of 3.0 M NaOH PROBLEM: You have 50.0 mL of 3.0 M NaOH and you want 0.50 M NaOH. What do you and you want 0.50 M NaOH. What do you do?do?

3.0 M NaOH 0.50 M NaOH

H2O

Concentrated Dilute

But how much water But how much water do we add?do we add?

PROBLEM: You have 50.0 mL of 3.0 M NaOH PROBLEM: You have 50.0 mL of 3.0 M NaOH and you want 0.50 M NaOH. What do you and you want 0.50 M NaOH. What do you dodo??

PROBLEM: You have 50.0 mL of 3.0 M NaOH PROBLEM: You have 50.0 mL of 3.0 M NaOH and you want 0.50 M NaOH. What do you and you want 0.50 M NaOH. What do you dodo??

How much water is added?How much water is added?

The important point is that --->The important point is that --->

moles of NaOH in ORIGINAL solution = moles of NaOH in ORIGINAL solution = moles of NaOH in FINAL solutionmoles of NaOH in FINAL solution

PROBLEM: You have 50.0 mL of 3.0 M NaOH and PROBLEM: You have 50.0 mL of 3.0 M NaOH and you want 0.50 M NaOH. What do you do?you want 0.50 M NaOH. What do you do?PROBLEM: You have 50.0 mL of 3.0 M NaOH and PROBLEM: You have 50.0 mL of 3.0 M NaOH and you want 0.50 M NaOH. What do you do?you want 0.50 M NaOH. What do you do?

Amount of NaOH in original solution = Amount of NaOH in original solution =

M • V = M • V =

(3.0 mol/L)(0.050 L) = 0.15 mol NaOH(3.0 mol/L)(0.050 L) = 0.15 mol NaOH

Amount of NaOH in final solution must also Amount of NaOH in final solution must also = 0.15 mol NaOH= 0.15 mol NaOH

Volume of final solution =Volume of final solution =

(0.15 mol NaOH)(1 L/0.50 mol) = 0.30 L(0.15 mol NaOH)(1 L/0.50 mol) = 0.30 L

or or 300 mL300 mL

PROBLEM: You have 50.0 mL of 3.0 M NaOH PROBLEM: You have 50.0 mL of 3.0 M NaOH and you want 0.50 M NaOH. What do you and you want 0.50 M NaOH. What do you do?do?

PROBLEM: You have 50.0 mL of 3.0 M NaOH PROBLEM: You have 50.0 mL of 3.0 M NaOH and you want 0.50 M NaOH. What do you and you want 0.50 M NaOH. What do you do?do?

Conclusion:Conclusion:

add 250 mL add 250 mL of waterof water to to 50.0 mL of 50.0 mL of 3.0 M NaOH 3.0 M NaOH to make 300 to make 300 mL of 0.50 M mL of 0.50 M NaOH. NaOH.

3.0 M NaOH 0.50 M NaOH

H2O

Concentrated Dilute

A shortcutA shortcut

MM11 • V • V11 = M = M22 • V • V22

Preparing Solutions by Preparing Solutions by DilutionDilution

Preparing Solutions by Preparing Solutions by DilutionDilution

THE

END