Acids and Bases

What is an acid?An acid is a solution that has an

excess of H+ ions. It comes from the Latin word acidus that means "sharp" or "sour".

The more H + ions, the more acidic the solution.

AcidsSubstances that donate hydrogen ions (H+) to

water to form H3O+ Called the hydronium ionHCl hydrochloric acid used in poolsH2SO4 sulfuric acid- battery acid

HC2H3O2 acetic acid- vinegar

HC6H7O7 citric acid- lemons, limes

Properties of an Acid

Tastes Sour Conduct Electricity Corrosive, which means

they break down certain substances. Many acids can corrode fabric, skin, and paper

Some acids react strongly with metals and form H+

Turns blue litmus paper red

Picture from BBC Revision Bites http://www.bbc.co.uk/schools/ks3bitesize/science/chemistry/acids_bases_1.shtml

AcidsThe ones in food are diluteConcentrated acids are dangerousThey can burn you skin and eyesStrong acids ionize completely

All the H’s make hydroniumHCl + H2O Cl- + H3O+

Makes lots of ionsAre dangerous

AcidsWeak acids only partially ionize

Only a few H’s attach to waterHC2H3O2+ H2O C2H3O2

- + H3O+

Can be dangerous if concentrated

Uses of Acids (list 3 Examples)Acetic Acid = VinegarCitric Acid = lemons,

limes, & oranges. It is in many sour candies such as lemonhead & sour patch.

Ascorbic acid = Vitamin C which your body needs to function.

Sulfuric acid is used in the production of fertilizers, steel, paints, and plastics.

Car batteries

What is a base?

A base is a solution that has an excess of OH- ions.

Another word for base is alkali.

Bases are substances that can accept hydrogen ions

BasesIncreases the amount of OH- in solutionEither has OH- in itOr takes an H off of waterKOH - in drain cleanerNaOH - in drain cleanerNH3- ammonia

Properties of a Base

Feel SlipperyTaste BitterCorrosiveCan conduct electricity.

(Think alkaline batteries.)Do not react with metals.Turns red litmus paper

blue.

BasesKOH K+ + OH-

Strong bases ionize completelyMake lots of ionsAre dangerous NH3 + H2O NH4

+ + OH-

Weak bases only make a few ionsAre dangerous if concentrated

Uses of Bases (List 3 Examples)Bases give soaps, ammonia,

and many other cleaning products some of their useful properties.

The OH- ions interact strongly with certain substances, such as dirt and grease.

Chalk and oven cleaner are examples of familiar products that contain bases.

Your blood is a basic solution.

pH ScalepH is a measure of how acidic or

basic a solution is.• The pH scale ranges from 0 to 14.

Acidic solutions have pH values below 7

A solution with a pH of 0 is very acidic.

A solution with a pH of 7 is neutral.• Pure water has a pH of 7.

• Basic solutions have pH values above 7.

pH Scale

• A change of 1 pH unit represents a tenfold change in the acidity of the solution.

• For example, if one solution has a pH of 1 and a second solution has a pH of 2, the first solution is not twice as acidic as the second—it is ten times more acidic.

Acid – Base Reactions

A reaction between an acid and a base is called neutralization. An acid-base mixture is not as acidic or basic as the individual starting solutions.

Neutralization ReactionsAcids and bases react and neutralize each

otherStrong acids make lots of ionsHCl + H2O H3O+ + Cl-

Strong bases make lots of ionsNaOH Na+ + OH-

andH3O+ + OH- 2H2O

Neutralization ReactionsPut acids and bases togetherH3O+ + Cl- + Na+ + OH- Cl- +Na+ +2H2OThe Na+ and Cl- make salt which is neutralWater is neutralAll ionic compounds are saltsWill be neutral if the right amounts of strong

acids and bases are added

Neutralization ReactionsWeak bases will neutralize a strong acid,

but not as well.You need to add more of themIf you add enough, it will make the

solution basicSame works for weak acids and strong

basesAs you add acid to a base the pH dropsAs you add base to and acid the pH rises

Acid – Base reactions

Each salt listed in this table can be formed by the reaction between an acid and a base.

SoapWater and oil don’t mixWater is polarOil is nonpolarSoap can dissolve in both oil and waterMade by mixing fats with lye (NaOH)

SoapC O-

CH3

CH2 CH2

CH2CH2

CH2

CH2

CH2

O-

O-

Soap

Hydrophobic non-polar end

C O-

CH3

CH2 CH2

CH2CH2

CH2

CH2

CH2

O-

O-

Soap

Hydrophilic polar end

C O-

CH3

CH2 CH2

CH2CH2

CH2

CH2

CH2

O-

O-

C O-

CH3

CH2 CH2

CH2CH2

CH2

CH2

CH2

O-

O-

_

A drop of grease in water

Grease is non-polarWater is polarSoap lets you dissolve

the non-polar in the polar.

Hydrophobic ends dissolve in

grease

Hydrophilic ends dissolve in

water

Water molecules can surround and dissolve grease.

Helps get grease out of your way.

DetergentsSoaps react with minerals in hard water and

form scum that doesn’t dissolveDetergents have the same basic structure but

have a sulfur at the end,And start from petroleumDissolve in hard water

AmmoniaNH3 dissolved in water makes a weak base

NH3 + H2O NH4+ + OH-

The OH- ion reacts with grease and makes an emulsion which can wash away

Slippery

Household Uses (List 3 Examples)Antacids- Weak bases that neutralize excess

stomach acidShampoo- made from detergentsNeed to keep pH between 5 and 8 or it will

make the hair dullCitric acid keeps fruit from browningAcidic marinades tenderize meatsDrain cleaners are strong bases