Acids and bases
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Transcript of Acids and bases
Chapter 7ACIDS AND
BASES
What is acid?
a substance that ionizes in water to produce hydrogen ions, H+
What is base?
a substance that reacts with an acid to form only salt and water
What is alkali?
Soluble bases that produce OH¯ ions in water
Chemical properties of acid Sour taste pH less than 7 Corrosive Conduct electricityAcid can react with a) bases to produce salts and water b) metals to produce salts and hydrogen gas c) carbonates to produce salts , carbon
dioxide gas and water
Chemical properties of base
Bitter/smooth/soapy pH more than 7 Corrosive Conduct electricityBase can react with a)Acid to produce a salt and water b)Heated with ammonium salt to produce
ammonia gasvideo
Uses of acids in daily lifeSulphuric acid – paints, detegents, polymers,
fertilisersCarbonic acid- make carbonated drinksEthanoic acid- vinegar
Uses of base in daily lifeSodium hydroxide – soaps, detergents,
bleaching agentsMagnesium hydroxide – toothpasteAmmonia- fertilisers
Role of water in the formation of hydrogen ions
In the presence of water, an acid will ionize to form the hydrogen ions, H +
So, water is essential for the formation of hydrogen ions that cause acidity
Role of water in the formation of hydroxide ions
In the presence of water, alkali will dissociate to form hydroxide ions, OH¯
Hence, water is essential for the formation of hydroxide ions that cause alkalinity
pH scale
A set of numbers used to show the degree of acidity and alkalinity of a solution
pH values of less than 7 indicates an acidic solution
pH values of more than 7 indicates an alkaline solution
pH values of 7 indicates a neutral solution
pH values
Higher pH value more alkalinehigher concentration of hydroxide ion
Lower pH value more acidichigher concentration of hydrogen ion
When acids meets base
• pH is actually a measurement of the concentration of hydrogen, H+ in a solution
• The higher the concentration of the H+
ions, the lower the pH value, and more acidic the solution is
• The higher the concentration of the OH¯ ions, the higher the pH value and the more alkaline solution the solution is.
Acid
Strong acid is an acid that dissociate (ionize ) completely in water to form hydrogen ion,H+ of high concentration
Weak acid is an acid that dissociate (ionize ) partially in water to produce hydrogen ions,H+
of low concentration.
• Mineral acids such as hydrochloric acid, nitric acid, and sulphuric acid are strong acids
• Weak acids-ethanoic acid, methanoic acid, citric acid, tartaric acid
Alkali
Strong alkali is produce when a base dissociates completely in water to produce hydroxide ions, OH- of high concentration
Weak alkali is produced when a base dissociates partially to produce hydroxide ions, OH- of low concentration.
• Strong alkali- sodium hydroxide, potassium hydroxide
• Weak alkali- ammonia solution
EDITED BY :
Noor Laili binti Mohamad EliasD20091034948
ISMP KIMIA 2009/2010
Thank you