ACIDS AND BASES

Acids An acid is a substance that

produces hydrogen ions (H+) when in solution with water

Water (H2O) is made up of even amounts of H+ and OH- ions. Water is NEUTRAL because of this. When an acid dissolves in water, this changes the amount of H+ ions.

Examples of acids include hydrochloric acid, citric acid, acetic acid (vinegar)

Properties of Acids

The more H+ ions it produces, the more acidic the solution

Strong acids are very dangerous. They have a high H+ concentration.

Weak acids are less dangerous. They have a low H+ concentration

Acids

Acids occur naturally in many fruits Sore muscles and sour milk are

cause by the same acid (lactic acid) Acids add a tangy, sour flavours to

foods and drinks Some are deadly!

Bases A base is a substance that

produces hydroxide ions (OH-) when in solution with water.

When a base is added to water it increases the amount of OH- ions

Another word for basic is alkaline Example: Sodium hydroxide

(NaOH)

Properties of Bases

The more OH- ions it produces, the more basic (alkaline) the solution

Strong bases are as dangerous as strong acids. They have a high OH-

concentration. Similarly, weak bases are like weak

acids with a low OH- concentration

Bases

Bases are bitter-tasting compounds They have a slippery feel Bases are in most soaps, drain and

window cleaners. They can be found in many

pharmaceutical drugs Some bases are deadly!

pH Scale

pH means “power of the hydrogen ion”

A pH scale is a measure of the acidity of a solution

In pH the “p” is always lower case, even at the start of a sentence.

pH scale

The pH scale has a useful range of numbers between 0 and 14.

A solution with a pH of 7 is neutral (like water)

Below pH 7, a solution is acidic Above pH 7, it is basic

pH Scale

Paper testing Paper tests like litmus paper and pH

paper

pH meter

Tests the voltage of the electrolyte

Converts the voltage to pH Very cheap, accurate Must be calibrated with a buffer

solution

pH indicators Indicators are dyes that can be

added that will change color in the presence of an acid or base.

Some indicators only work in a specific range of pH

Once the drops are added, the sample is ruined

Some dyes are natural, like radish skin or red cabbage

Neutralization When an acid and a base react

together their pH becomes neutral.

Acid + base salt + waterEx: HCl(aq) + NaOH(aq) NaCl(aq) + H2O(l)

This is a double displacement!

ACID-BASE NEUTRALISATION

Neutralisation Reaction:Acid + Base Salt + Water

Ex: HCl + NaOH NaCl + H2O

The acid and base neutralise each other creating a salt and water

Must be equal concentrations of acid and base

Actually a Double Displacement Reaction!

HNO3 + KOH KNO3 + H2O

HF + NaOH NaF + H2O

HCl + Ca(OH)2 CaCl2 + H2O 2 2

acid + base salt + water

1. Ba(OH)2 + H3PO4

2. HC2H3O2 + NaOH

3. H2SO4 + KOH

4. H2CO3 + NaOH

5. Na2CO3 + HCl