Acids and Bases(You may not know it, but they’re everywhere!!)

Everyday Acids

Acids make food taste sour Lemon and orange juice contains citric acid Vinegar contains acetic acid Milk products (and sore muscles) contain

lactic acid

Stomach acid helps digest food

Car batteries contain sulfuric acid

Everyday Bases

Soaps and cleaners contain basesAmmonia (NH3)

Bleach (NaClO)

Antacids contain bases Milk of magnesia is magnesium

hydroxide

Baking soda is sodium bicarbonate (NaHCO3)

Physical Properties of Acids and Bases

Property Acids BasesColour of Red Litmus Paper No change (red) Blue

Colour of Blue Litmus Paper Red No change (blue)

Colour when Phenolphthaline Indicator is added

No change (clear and colourless)

Bright pink

Colour when Red Cabbage Juice Indicator is added

Red Yellow

Taste Sour Bitter Texture Water-like Slippery Solubility in Water Very good

Form ions Very good Form ions

Electrical Conductivity Very good because acids form ions in water

Very good because bases form ions in water

Chemical Properties of Acids and BasesProperties Acids Bases

Chemical Reactivity

Very corrosive React with some

metals to produce H2 gas

React with carbonates

React with bases to produce a salt and water (neutralization reactions)

Somewhat corrosive

Break down proteins (denaturation reactions)

React with acids to produce a salt and water (neutralization reactions)

Commercial Uses

Used as catalysts Used in refining oil,

making fertilizers, electroplating metals

Used in antacids, cleaners

Acids and Bases “Ionize” in Water

This means that the bonds between ions in acids (or bases) break when they dissolve in water

That leaves the ions free to float around separately

That’s what makes acids and bases good conductors of electricity!

H2O

H2O

H2O

H2O

H2O

H2O

H2O

H2O

H2OH2O

H+ H+

H+

H+

H+H+

H+

H+ Cl-

Cl-

Cl-

Cl-

Cl-

Cl-

Cl-

Cl-

H2O

Acids are Proton (H+ ion) Donors

When dissolved in water, one of the ions that an acid releases is H+ Strong acids are 100% (or nearly so) ionized in water Therefore, they are good H+ donors

HCl H2SO4 HNO3

hydrochloric acid sulfuric acid nitric acid

Weak acids are usually less than 5% ionized in solution

Therefore, they are poor H+ donors

H3PO4 HC2H3O2

phosphoric acid acetic acid

Bases are Proton (H+ ion) acceptors

Bases also ionize in solution

One of the ions released by a base is often an hydroxide ion

(OH-)

NaOH KOH Ca(OH)2

sodium hydroxide potassium hydroxide calcium hydroxide

Bases are also classified as weak or strong based on the

degree of ionization in water The OH- from a base, combines with the H+ from an acid to

form water

H+ + OH- → H2O

Acids and Bases “Neutralize” Each Other

Acids and bases react in “NEUTRALIZATION”

reactions

The reactants are always an acid and a base

The products always include a salt and water

HCl + NaOH → NaCl + H2O

acid base salt water

Measuring Acids and Bases

Acids and bases have a unique scale for measuring their

relative strength

It’s called the pH scale

pH stands for the “power of hydrogen” because the scale is

based on the concentration of H+ ions in solution

The scale goes from 0 to 14

Acids have a pH less than 7 (H+ > OH-)

Bases have a pH greater than 7 (H+ < OH-)

Distilled water has a pH of 7 which is neutral (H+ = OH-)

The pH Scale

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

NeutralVery Acidic Very Basic

(Alkaline)

more H+ than OH- more OH- than H+

H+ equals OH-

The pH scale is logarithmic That means that the space between successive numbers represents a 10X increase or decrease