Post on 28-Dec-2015
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