Acids, Bases, and Salts Module 6: Characteristics of Acids and Bases Strong and Weak Acids and Bases Ionization of Water pH and pOH Neutralization Reactions

Acids, Bases, and SaltsModule 6:

Characteristics of Acids and Bases

Strong and Weak Acids and Bases

Ionization of Water

pH and pOH

Neutralization Reactions

Buffers

How Buffers Maintain pH Constant

Acidosis and Alkalosis

Properties of Acids

Produce hydrogen (H+) or hydronium (H3O+) ions when dissolved in water

Taste: Sour Are electrolytes. (Electrolytes are substances that conduct

electricity.) Turns blue litmus paper red Neutralizes bases Has a pH level ranging from -1 to 7

Properties of Bases

Produce OH- in aqueous solutions. Taste: Bitter Turn red litmus paper blue Are electrolytes. e) React with acids. f) Feel slippery or soapy Has a pH level ranging from 7 to 14

Acids and Bases

H2O

Acid Base

MOH

hydroxide ion written at end

metal or ammonium ion

Strong and Weak Acids and Bases

Strong acids and bases dissociate completely, so they are considered strong electrolytes

Compounds that dissociates less than 50% are considered weak electrolytes (weak acids and bases).

Strong Acids

Strong Acid: are strong electrolytes.

Strong acids ionize completely.

A strong acid examples are: HCl, HBr, HI, HClO4, HNO3, H2SO4

Strong Bases

Strong Base: are also strong electrolytes

All salts/bases dissociate 100%

A strong base consists of:a [Group 1A metal] + [Hydroxides] and Ca(OH)2 , Sr(OH)2 , Ba(OH)2

Acids and Bases

Substance Strong Electrolyte

Weak Electrolyte

HBr

Ni(OH)2

KOH

HCN

Tap water

Acids and Bases

Substance Strong Electrolyte

Weak Electrolyte

HBr

Ni(OH)2

KOH

HCN

Tap water

Ionization of Water

The above equation is often simplified as follows:

H+ + OH- H2O

H2O + H2O H3O+ + OH-

hydronium hydroxide

The double arrow indicates that this is an equilibrium

http://www.chem.umass.edu/genchem/whelan/class_images/110_pH_Scale.jpg

pH and pOH

Notice that pH + pOH = 14

0123456

141312111098

100

10-1

10-2

10-3

10-4

10-5

10-6

10-14

10-13

10-12

10-11

10-10

10-9

10-8

7 7 10-7 10-7 neutral

891011121314

6543210

10-8

10-9

10-10

10-11

10-12

10-13

10-14

10-6

10-5

10-4

10-3

10-2

10-1

100

pH pOH [H+] [OH-]

pH and pOH

pH pOH [H+] [OH-] acidic, basic, or neutral

11

10-9

7

10-4

pH and pOH

pH pOH [H+] [OH-] acidic, basic, or neutral

3 11 10-3 10-11 acidic

9 5 10-9 10-5 basic

7 7 10-7 10-7 neutral

10 4 10-10 10-4 basic


the salt is formed when the positive ion from the base combines

with the negative ion from acid

water is formed when H+

combines with OH-

NaCl + HOHHCl + NaOH


NiCl3 + LiOH Ni(OH)3 + LiCl



NiCl3 + LiOH Ni(OH)3 + 3 LiCl



NiCl3 + LiOH Ni(OH)3 + 3 LiCl

NiCl3 + 3 LiOH Ni(OH)3 + 3 LiCl

Buffers

•A buffer solution is a solution whose pH remains relatively constant when either acids or bases are added to it.

•Buffers do not have an unlimited ability to resist pH changes. This is the buffering capacity.

Buffers

•A buffer solution is a solution whose pH remains relatively constant when either acids or bases are added to it.

•Buffers do not have an unlimited ability to resist pH changes. This is the buffering capacity.

Buffers•Buffers must be able to react with excess acid or excess base

•It has two components•one to react with the acid and •one to react with the base

•Most common buffers consist of:•a weak acid and its salt or •a weak base and its salt

Example Calculate the mass of NaCl found in 200

mL of 6.0% (m/v) NaCl solution.

iongNaClsolutmLsolution

gramsNaClmLsolution

12100

06200

.

Example What volume of a solution that is 5.0% (m/v)

copper (II) nitrate contains 50.0g of Cu(NO3) 2?

Example What volume of a solution that is 5.0% copper

(II) nitrate contains 50.0g of Cu(NO3) 2?

mLsolution

NOgCuNOCu

100

0505 23

23

)(.)(%.



23

23 05

100050

)(.)(.

NOgCu

mLsolutionNOgCu



mLsolution

NOgCu

mLsolutionNOgCu

1000

05

100050

2323

)(.)(.

Example

Calculate the percent v/v of a solution prepared by dissolving 25 ml of ethanol in 50mL water (assume the volumes are additive).

Example Calculate the percent v/v of a solution prepared

by dissolving 25 ml of ethanol in 50mL water (assume the volumes are additive).

First, we need to determine the total volume of the solution:

25mL ethanol + 50 mL water = 75 mL solution

Example




mLsolution

mLethanol

75

25

Example




10075

25

mLsolution

mLethanol

Example




solution ethanol %3310075

25

mLsolution

mLethanol

Molarity

Molarity

Moles solute = M Liter of solution

Example What is the molarity (M) of a solution that

contains 30.0g copper (II) nitrate in 250mL solution?



30 01

187 53 2

3 2

3 2

. ( )( )

. ( )gCu NO

moleCu NO

gCu NO



30 01

187 5

0160

3 2

3 2

3 2

3 2

. ( )( )

. ( )

. ( )

gCu NOmoleCu NO

gCu NO

moleCu NO



2501

1000mLsolution

Lsolution

mLsolution



2501

10000 250

mLsolutionLsolution

mLsolutionLsolution

.



0160

0 2503 2. ( )

.

moleCu NO

Lsolution



0160

0 2500 640

3 2

3 2

. ( )

.. ( )

moleCu NO

LsolutionMCu NO

Example Calculate the mass of NaOH needed to

prepare 150mL of a 0.220M solution of sodium hydroxide.



Lsolution

moleNaOHMsolution

1

22002200

..



mLsolution

LsolutionmLsolution

1000

10150 .



Lsolution

mLsolution

LsolutionmLsolution

1500

1000

10150

.

.



moleNaOH

gNaOH

Lsolution

moleNaOHLsolution

1

040

1

22001500

...



gNaOH

moleNaOH

gNaOH

Lsolution

moleNaOHLsolution

321

1

040

1

22001500

.

...

Dilutions

V1 X C1 = V2 X C2

where C is concentration, it may be Molarity, mass%, or other concentration units

Example Calculate the volume of 6.0MKCl needed to prepare

250mL of a 0.300M solution of potassium chloride.


250mL of a 0.300M solution of potassium chloride. V1 X C1 = V2 X C2



(? )( . )( )( . . )

(? )

mL MKClsolutionmL Msol

mL

6 0250 0 300



(? )( . )( )( . . )

(? )

mL MKClsolutionmL Msol

mL

6 0250 0 300

Solutions, Colloids and Suspensions

SOLUTION COLLOIDS SUSPENSIONS

Solute Particles: small particles(ions or molecules)

larger particles very large particles(macromolecules)

Examples:

salted water, beer starch and water, fog, smoke, sprays

calamine lotion

Characteristics:

Transparent.Particles cannot be separated by filters or semipermeablemembranes.

Tyndall Effect.Particles can be separated by semi-permeablemembranes.

Opaque.Particles can be separated by filters.

Osmosis

The flow of a solvent through a semipermeable membrane into a solution of higher solute concentration.

A semipermeable membrane, such as cellophane, contains tiny holes far too small to be seen but large enough to let solvent molecules pass through, but NOT large solute particles.

Osmosis

• Compartment A – pure water

• Compartment B – glucose solution

dissolved

A B

Osmosis

dissolved

A B osmotic pressure

Osmosis reaches an equilibrium and the level of compartment B is higher than A. These levels can be made equal again by applying an external pressure to compartment B. The amount of pressure necessary to equalize both levels is called osmotic pressure.

Osmotic PressureDepends on the number of particles in the solution. In the blood,

Solution Osmotic pressure

Examples

hypotonic Lower than red blood cells

Pure water, solutions LESS than 5% glucose, 0.9% NaCl solution

isotonic Same as red blood cells

Plasma, 5% glucose, 0.9% NaCl solution

hypertonic Higher than red blood cells

Solutions GREATER than 5% glucose, 0.9% NaCl solution

Dialysis

Uses a semipermeable membrane to separate dissolved ions and molecules from larger colloidal particles dispersed in the solution.

In kidneys the waste products of the blood dialyze out through a semipermeable membrane.

Acid, Bases and Salts

THE END

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Acids, Bases, and Salts Module 6: Characteristics of Acids and Bases Strong and Weak Acids and Bases Ionization of Water pH and pOH Neutralization Reactions