Acids & Bases

Batman (1989)

Jack Napier The Joker

Acids & Bases and Your Body

• Both play many different roles• Acids– Some are harmful (H2CO3)– Some are essential (DNA)

• Bases– Harmful (NH3)– Helpful (saliva)

Identifying Acids & Bases

• Thousands of years ago chemists used taste as a way to identify acids and bases.– Acids = sour– Bases = bitter

• This process however, is not safe!!

pH and the pH scale

• power of hydrogen• ph is the most common way of determining

acids/bases today• Related to the # of hydrogen ions (H+) that are

in a solution• # scale that shows how acidic or basic a

solution is......

ph Scale

Acids Bases

Increasingly acidic Increasingly basicN

eutr

al

• ph = 7 (neutral)....water

• ph = 0-6 (acid)....lemon juice

• ph = 8-14 (base)....baking soda

Acid/Base Indicators• Most common indicator is litmus• Plant extract that can either be red or blue

• Red litmus paper turns blue when dipped into a basic solution

• Blue litmus paper turns red when dipped into an acidic solution

ACID REDBASEBLUE

Universal Indicator (UI)• Mixture of chemicals that changes colour

through a wide range of pH values• pH paper are embedded with UI

Identifying Acids

• Usually the name of an acid ends with the word “acid”

• If you are given a chemical formula you know its an acid if:– It starts with H (hydrogen) or– It ends with COOH (carboxyl polyatomic ion)

• Examples– HF (hydrofluoric acid)– CH3COOH (acetic acid)

Naming Acids

• Two rules:1. When chemical formula starts with H and only has

one other non-metal element– Start with prefix hydro– Add suffix “ic” to ending of non-metal and then the

word “acid”• Example– HCl– Hydrochloric acid– Hydrochloric acid

Naming Acids

2. When polyatomic ion in an acid has an oxygen and ends in “ate”– Start with the name of the element in the polyatomic ion that

is NOT oxygen– Add suffix “ic” to ending of non-metal and then the word

“acid”

• Example– H2SO4

– Sulphuric acid– Sulphuric acid

Identifying Bases

• Bases begin with the name of a metallic ion and end with the word “hydroxide”

• A substance is also a base if:– Chemical formula starts with ammonium ion (NH4)

or– Ends with hydroxide (OH)

Naming Bases

• Write the name of the + metallic ion that is at the beginning of the chemical formula

• Add “hydroxide”• Example– KOH– Potassium Hydroxide

Homework

• Page 203• Questions # 1-10