Acids and Bases

Acids and Bases

Aliyev Shahzodbek

Grade 8-blue

Indicators and pH scales

• The range goes from 0 - 14, with 7 being neutral. pH of less than 7 indicate acidity, whereas a pH of greater than 7 indicates a base.
• pH 0 is most strong acid while pH 14 most strong alkaline.

Acids

• Common acids: Hydrochloric acid(HCl), Sulfuric acid(H2SO4), Nitric acid(HNO3), Ethanoic acid(CH3COOH)
• An acid is any substance that in water solution tastes sour, changes blue litmus paper to red, reacts with some metals to liberate hydrogen, reacts with bases to form salts, and promotes chemical reactions (acid catalysis).
• Metal + Acid  Salt + hydrogen
• Carbonate + Acid  Salt + water + CO2

Strong and weak acids.

Bases (alkalis)

• Base is a compound with particular chemical properties including turning litmus blue and neutralizing or effervescing with acids; typically, a caustic or corrosive substance of this kind such as lime or soda.
• Some common alkalis:

Sodium hydroxide NaOH

Potassium hydroxide KOH

Calcium hydroxide Ca(OH)2

Ammonia NH3

Metal + Base  Metal salt + Hydrogen gas

Strong and weak alkalis

Indicators

• pH indicators are weak acids that exist as natural dyes and indicate the concentration of H+ (H3O+) ions in a solution via color change. A pH value is determined from the negative logarithm of this concentration and is used to indicate the acidic, basic, or neutral character of the substance you are testing.
• Example of indicator is Litmus
• Acid + base  salt + water

Neutralisation

• When you add an alkali to an acid a chemical reaction occurs and a new substance is made. If exactly the right amounts of acid and alkali are mixed, you will end up with a neutral solution. This is called a neutralisation reaction.