1. Day 14 – Identification of Acids and Bases and pH Scale
SCI 10 Chemistry

2. Examples of acids Lactic acid in muscles
Digestive acids in the stomach
Acids in certain fruits (pineapples, oranges)

3. Examples of bases Soaps and cleaning products
Lidocaine (local anesthetic used by dentists)

4. How Can We Identify Acids & Bases?
Many acids and bases look the same – transparent liquids
How to tell them apart?
Using indicators
Indicator: a chemical that changes colour as the concentration of H+ and OH- changes
i.e.: phenolphthalein and litmus

5. Indicators Phenolphthalein: Litmus (from lichens)
In the presence of an acid: colourless
In the presence of a base: pink
Litmus (from lichens)
Blue litmus turns red in
the presence of an acid
Red litmus turns blue in
the presence of a base

6. The pH Scale (the power of H)
pH: a scale that indicates the concentration of hydrogen
A measure of the acidity of a solution
0 to 14:
pH < 7 = acid
pH > 7 = base
pH 7 = neutral
pH is found using pH paper or a pH meter

7. Highest concentration of OH- (Lowest concentration of H+)
Highest concentration of H+
(Lowest concentration of OH-)

8. Characteristics of Acids & Bases p.160
Taste
Feel
Litmus paper
With metals
Conducts electricity pH

9. Reactions Between Acids & Bases
ACID + BASE → H2O + SALT
NEUTRALIZATION
Neutral pH at the end
Ex: Hydrochloric acid in stomach + Magnalax antacid magnesium hydroxide)
2HCl (aq) + Mg(OH)2 → 2H2O (l) + MgCl2