ACIDS & BASESmodule 1- 2013

i. An acid is a chemical substance that …………………in water to produce ………………. ions.

ii. A base is a chemical substance that ………………in water to produce ………………. ions .

iii. Base can be classify as metal oxide or metal hydroxide for example Zinc Oxide (ZnO), Zinc Hydroxide (Zn(OH)2 )

DEFINITIONS OF ACIDS, BASES AND ALKALIS

ionizeshydrogen

ionizeshydroxide

i. Alkalis are ……………………. that dissolve in ………………… to produce hydroxide ions, OH-

Example of alkali : Potassium Oxide, K2O, Potassium Hydroxide, KOH, Sodium Oxide, Na2O, Sodium Hydroxide, NaOH, Ammonium Hydroxide, NH4OH

baseswater

Ionize equation:

ClHHCl 2

442 2 SOHSOH 33 NOHHNO

COOCHHCOOHCH 33

COOHCHCOOHHC 5252

NOTE : Hydrogen ion, H+ must FREE TO MOVE in WATER to show ACIDIC PROPERTIES

OHKKOH

OHNaNaOH

OHNHOHNH 44

COMPOUND CHEMICAL FORMULA

CLASSIFIED

Sodium oxideCalcium oxideHydrochloric acidCalcium hydroxideEthanoic acidAmmonia

3)Classify these substances into strong and weak acids, bases and alkali

Na2O base CaO base HCl strong acid Ca(OH)2 strong alkali

CH3COOH weak acid NH3 Base

•Base is oxides or hydroxides metals, •alkali is soluble hydroxides ( KAN) and Ba(OH)2 and Ca(OH)2

COMPOUND CHEMICAL FORMULA

CLASSIFIED

Lead (II) oxidePotassium oxideBarium HydroxideNitric acidSulphuric acid Magnesium oxide

•Base is oxides or hydroxides metals, •alkali is soluble hydroxides ( KAN) and Ba(OH)2 and Ca(OH)2

PbO Base K2O base

Ba(OH)2 Alkali

HNO3 Strong acid H2SO4 Strong acid

MgO Base

USES OF ACIDS IN DAILY LIFE

Methanoic acid Nitric

acid

benzoic acid

hypochlorousacid

carbonicacid

hydrochloricacid

sulphuricacid

USES OF ALKALIS IN DAILY LIFE

Magnesium hydroxide

Sodium hydroxideMagnesium Hydroxide /Aluminium hydroxide

ammoniasodium

hydroxide

PROPERTIES OF ACID AND ALKALI(I) ACIDTaste ________ and turn moist _______ litmuspaper to ______

sour bluered

Chemical Properties of Acid(1) REACTION WITH METALS that is more electropositive than hydrogen in the electrochemical series to produce SALT AND HYDROGEN

Acid + Metal salt + Hydrogen

gas 2HCl + Zn ZnCl2 + H2

a) Fill in diagram c) aboveb) What can you observe when zinc powder is added to hydrochloric acid solution ? - bubble of colourless gas released - Zinc powder dissolves

c) Which substance is an acid? Hydrochloric acid

d) Which substance is a metal? zinc e) Name the gas that is produced.

hydrogen gas

f) Name the salt formedzinc chloride

1. Black powder dissolved2. Blue solution is formed

Blue solid formed

Sulphuric acid

Copper (II) oxide

Copper(II) sulphate

Colourless gas evolved that turn lime water cloudy

Calcium carbonate

Carbon dioxideCalcium nitrate

BITTER RED BLUE

DISSOLVE

CRYSTAL

ROOM

BLUE AMMONIA

GREEN

HYDROGEN ION

ACID MOLECULES IONISES IN WATER to form hydrogen ion

EXP 1 AND 3, no hydrogen ion present

EXP 2, HYDROGEN ION FROM ACID REACT WITH MAGNESIUM TO PRODUCE HYDROGEN GAS

Water IONISES THE ACID MOLECULES TO PRODUCE HYDROGEN IONS

• What is the role of propanone?

• What is the ion that is responsible for litmus paper to change colour?

As an Organic solvent to dissolve ammonia

Hydroxide ion

Which experiment does not show alkaline property ? Why?

What is the role of water in showing the properties of alkali?

Experiment 1 and 3. Because no presence of hydroxide ion

Water ionizes alkali and produce hydroxide ion. The Hydroxide ion will show the alkali property

THE STRENGTH OF ACID AND ALKALI

D: Complete table belowGIVE DEFINITIONS GIVE EXAMPLES

STRONG ACID

WEAK ACID

An Acid that ionizes completely in water to produce high concentration of hydrogen ion

An Acid that ionizes partially in water to produce low concentration of hydrogen ion

Hydrochloric acid, Nitric Acid, Sulphuric acid

Ethanoic acid, Methanoic acid,benzoic acid

GIVE DEFINITIONS GIVE EXAMPLES

STRONG ALKALI

WEAK ALKALi

An Alkali that ionizes completely in water to produce high concentration of hydroxide ion

Sodium Hydroxide, Barium Hydroxide

An Alkali that ionizes partially in water to produce low concentration of hydroxide ion

Ammonia aqueous / Ammonium Hydroxide,

E: What is the relationship between• the concentration of hydrogen ions and the pH

value

• the degree of ionization and the concentration of hydrogen ions

• degree of ionization and the strength of acid

The higher the concentration of hydrogen ion, the lower the pH value

The higher the degree of ionization, the higher the concentration of hydrogen ion

The higher the degree of ionization, the stronger an acid

SOAP

coffee

3.0 banana

5.0 Vinegar

Hydrochloric acid

Tooth paste

F : Place in pH values for the following substances

2.8 4.0

7.81 6.5-6.8

3.5

6.5

8.08.2

• The pH value for hydrochloric acid 0.1 mol dm-3 is 1 , Whereas pH value of ethanoic acid of the same concentration is pH 3 . Explain.

Hydrochloric acid is a strong acid that ionizes completely in water to produce high concentration of hydrogen ion.

While Ethanoic acid is a weak acid that ionizes partially in water to produce low concentration of hydrogen ion.

The higher the concentration of hydrogen ion, the lower the pH value

Therefore Hydrochloric acid have lower pH value than Ethanoic acid

2) What is the relationship betweenThe concentration of hydroxide ions and the pH

value

the degree of ionization and the concentration of hydroxide ions

\

The higher the concentration of hydroxide ion, the higher the pH value

The higher the degree of ionization, the higher the concentration of hydroxide ion

degree of ionization and the strength of alkali

The higher the degree of ionization, the stronger an alkali

• The pH value for sodium hydroxide 0.1 mol dm-3 is 13 Whereas pH value of ammonia solution of the same concentration is pH 11 . Explain

Sodium hydroxide is a strong alkali that ionizes completely in water to produce high concentration of hydroxide ion.

While ammonia is a weak alkali that ionizes partially in water to produce low concentration of hydroxide ion

•The higher the concentration of hydroxide ion, the higher the pH value

•Therefore Sodium hydroxide have higher pH value than ammonia