Acids, Bases, and Salts - SS1 Chemistry Past Questions and Answers - page 2

Acids and bases are two types of compounds that exhibit distinct chemical and physical properties.

 

Acids:

Acids are substances that release hydrogen ions (H+) when dissolved in water. They are characterised by their sour taste, ability to turn blue litmus paper red, and their corrosive nature. Acids have a pH less than 7. Common examples of acids include hydrochloric acid (HCl), sulfuric acid (H2SO4), and acetic acid (CH3COOH).

 

Bases:

Bases, also known as alkaline substances, are compounds that release hydroxide ions (OH-) when dissolved in water. They have a bitter taste, a slippery or soapy feel, and turn red litmus paper blue. Bases have a pH greater than 7. Examples of bases include sodium hydroxide (NaOH), potassium hydroxide (KOH), and ammonia (NH3).

Acids and bases have several distinct physical and chemical properties:

 

Physical Properties of Acids:

-       Sour taste: Acids taste sour, although it is not advisable to taste them due to their corrosive nature.

-       Colour change: Acids can change the colour of certain indicators. They turn blue litmus paper red and have no effect on red litmus paper.

-       Electrical conductivity: Acids conduct electricity when dissolved in water due to the presence of hydrogen ions (H+).

-       Corrosive nature: Acids can corrode or dissolve certain metals, as they react with metal atoms to produce hydrogen gas.

 

Physical Properties of Bases:

-       Bitter taste: Bases taste bitter, but, like acids, they should not be tasted due to their caustic nature.

-       Colour change: Bases turn red litmus paper blue and have no effect on blue litmus paper.

-       Slippery or soapy feel: Bases have a characteristic slippery or soapy texture.

-       Electrical conductivity: Bases conduct electricity when dissolved in water due to the presence of hydroxide ions (OH-).

Chemical Properties of Acids:

-       Reaction with metals: Acids react with certain metals, such as zinc or magnesium, to produce hydrogen gas and a salt.

-       Reaction with bases: Acids react with bases to form salts and water in a process called neutralisation.

-       Reaction with carbonates: Acids react with carbonates to release carbon dioxide gas, water, and salt.

 

Chemical Properties of Bases:

-       Reaction with acids: Bases react with acids in a neutralisation reaction, forming salts and water.

-       Reaction with fats and oils: Bases react with fats and oils to produce soap through a process called saponification.