Solutions of acids & bases

Prepared by the teacher: Ronak AhmedDuhok International School

2012-2013

Chemistry – Grade 9

If you eat large amounts of foods….!!

You’ll have a terrible case of indigestion

If you had an upset stomach, you’ll fell

a stomach ache. Antacids may help

you

How antacid is working?

• Antacid: is a weak base that neutralizes a strong acid in your stomach.

Strengths of Acids & Bases

• Acids & bases can be strong or weak.

The strength of an acid or a base is not the same as the concentration of an acid or base.

The concentration of an acid or a base

is the amount of acid or base dissolved in water.

The strength of an acid or base

Depends on the number of molecules that break apart when the acid or base is dissolved in water.

Strong acids & Weak AcidsAs an acid dissolves in water, the acid’s molecules break apart and produce hydrogen ions, (H+).

When an Acid is strong or weak?

If all of the molecules of an acid break apart

Strong acid Weak acid

If only a few molecules of an acid break apart

Sulfuric acidH2SO4

Car battery

Nitric acidHNO3

fertilizers

Hydrochloric acid HCl

stomach

Acetic acid(HC2H3O2)

vinegar

Citric acid (lemons)C6H8O7

Carbonic acid (soft drink)

H2CO3

Strong Bases & Weak Bases

When all molecules of a base break apart in

water to produce hydroxide ions (OH-)

Strong base Weak base

If only a few molecules of a

base break apart

Sodium hydroxide

NaOHSoap

Calcium hydroxideCa(OH)2

Cement

Ammonium hydroxide

NH4OHCleaners

Aluminum hydroxide

Al(OH)3

Antacid

Potassium hydroxideKOH

Battery electrolyte

Neutralization

When the base in an antacid meets stomach acid, a reaction occurs.

Neutralization: is the reaction between acids and base.

Why Acids & Bases neutralizing one another?

Hydrogen ions (H+)In acid

Hydroxide ions (OH-)In base

react

H2O

Neutral

Other ions from the acid and base dissolved in the water. when the water evaporates, these ions join to form a compound called a salt.

The pH Scale

An indicator such as litmus, can identify whether a solution contains an acid or base.

Acid base

The pH of a solution is a measure of the hydronium ion concentration in the solution.

• Solution PH =7 neutral

• Distilled water has a pH of 7.• Basic solutions pH = > 7.• Acidic solutions pH= < 7.

The solution is neither acidic nor basic

Use of indicators to determine pH

what is the role of combination of indicators?

It can be used to find out how basic or how acidic a solution is.

This can be done if the colors of the

indicators are known at different

pH value.

How the pH Indicator is working?

1. The strips of pH paper contain several different indicators.

2. These strips were dipped into two different solutions.

3. The pH of each solution is found by comparing the colors on each strip with the color of indicator scale provided.

Video

It is often used to test the pH of water in pools and aquariums.

Where this kind of indicator is used?

pH meter• Is another way to find the pH of a solution.• These pH meters can detect and measure hydronium

ion concentration electronically.

video

pH and the Environment • Living things depend on having a steady pH in their

environment. Prefer acidic soil, pH (4-6)

Need basic soil, pH (8-9)

Plants may also have different traits under different growing condition!

• Ex:

The color of hydrangea flowers

varies when the flowers are grown in

soils that have different pH values.

• Many organisms living in lakes and streams need a neutral pH to survive.

• Most rain has a pH between (5.5 and 6).When the rain is acidic and how?

When rainwater reacts with compounds found in air pollution, acids are formed and the rain water’s pH decrease.Most acid rain has a pH between (4 and 4.5).

Salts

• An ionic compound that forms when a metal atom replaces the hydrogen of an acid.

What will be produced if an acid neutralize a base?

A salt and water will be produced

Salts

Table salt is only one example of a large group of compounds that called salt

Uses of SaltsSalts have many uses in industry and in homes.

1. Sodium chloride used in foods

its also used to make other compounds,

including sodium hydroxide, soap &

sodium hydrogen carbonate.

2. Ammonium nitrate is a salt used to

make fertilizers.

3. Calcium sulfate is used to make wallboard (used

in construction).