Properties of Acids and Bases

And the pH scale

Properties of Acids The acids we eat can be described as:

Sour-tasting Examples of Common Acids

Acid (Common Name) Source or Use - Vinegar (10% Acetic Acid) Salad Dressing- Citric Acid Fresh Fruit- Ascorbic Acid Vitamin C- Carbonic Acid Carbonated Soft Drinks - Lactic Acid Sour Cream- Acetylsalicylic Acid Aspirin

Some acids react with metals and glass, these are described as corrosive. If released into the environment, these acids can cause serious damage.

Properties of Bases

The bases we eat can be described as: bitter-tasting slippery when rubbed between the fingers

Examples of Common BasesBase (Common Name) Source or Use- Sodium Bicarbonate Baking Soda- Potassium Sulphite Food Preservatives- Aluminum Hydroxide Antacid

Bases are good conductors of electricity because they release hydroxide ions (OH-) when dissolved in water. Some bases are just as dangerous as acids and can burn skin.

(Example: Sodium Hydroxide…Drain Cleaner & Ammonium Hydroxide…Window Cleaner)

The pH Scale

Acids and bases are pure substances and compounds. Some are called “weak” and some are called “strong.” Strong acids and bases are extremely reactive and corrosive. The strength of an acid is determined by its ability to produce

hydrogen ions when mixed with water. Example;

HCl – Hydrochloric Acid HF – Hydroflouric Acid H2SO4 – Sulfuric Acid

The number of hydrogen ions produced when an acid is mixed with water determines the acid properties of the solution. The greater the number of hydrogen ions, the lower the pH value.

The pH value is usually expressed on a scale from 0 to 14.

pH Values of less than 7 are acidic, greater than 7 are basic or alkaline. The number 7 is neutral (Pure water).

Contributors of strength

The strength of an acid or base is dependant on two factors The percent ionization

Percentage of H+ ions released by the molecule

Concentration

HCl a strong acid

Strong acids and bases

Percent ionization is the number of molecules out of 100 that will separate into the parts of an acid or base once placed in water

For example HCl will completely break apart in to H+ and Cl in water, this makes it a strong acid

This is dependant on how strong the bonds are between the atoms

Similarly with Bases, strong bases will release a high percentage of the OH- ions from the chemical bond

Concentration involves the number of H+ or OH- ions in a given unit of volume

Strong acid has low pH, high percent ionization, weak bond strength.

Strong base has high pH, high percent ionization, weak bond strength.

Examples

Strong Acids H2SO4 sulfuric HCl Hydrochloric HNO3 Nitric

Weak Acids H2CO3 Carbonic

Strong Bases NaOH Sodium KOH Potassium Ca(OH)2

? Mg(OH)2 ?

Weak bases NH3 Ammonia

Comparisons

Acids are Sour Strong acids are

corrosive Turns indicators red Reacts with metals Reacts with CO3

Does not react with ammonium chloride

Bases Bitter Strong bases are

corrosive Turns indicators blue Reacts with few metals Does not react with

CO3

Reacts to make NH`and water