Acids, Bases and Salts

Acids and Bases

You probably think of acid as a dangerous substance. But did you know that you consume acid every day? Most of the food that you eat is acidic in nature. For example, lemon is acidic in nature. However, there are a few food items that are basic in nature. How do you determine if a substance is acidic or basic? How do you use litmus paper? What is it?. Let’s find out more about acids and bases.

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Introduction to Acids

pH scale

The word “acid” is derived from the Latin word “acidus” which means tart or sour. Acids are molecules or other species that can donate a proton or accept an electron pair in reactions. All acids change the color of blue litmus paper to red. Acids lose their acidity when combined with alkalis. Generally, the pH value of acids ranges from zero to six.

Some common examples of acids are citrus fruits such as lemon and oranges which contain citric acid. Lemon also has ascorbic acid. Tamarind contains tartaric acid. Vinegar has Acetic acid. Apple consists of Malic acid. Lactic acid is found in milk and other dairy products. Insects like bees, ants, etc have formic acid in their stings. Mustard Oil has stearic acid.

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Properties Of Acids

The following are the properties of acids :

  • Acids turn the color of blue litmus paper to red.
  • All acids taste sour or tart.
  • Their pH range is from 0 to 6.
  • Acids lose their acidity when combines with bases.
  • They change the color of Methyl to Orange/Yellow to Pink.
  • Acidic substances convert Phenolphthalein from deep pink to colorless.
  • Acids reduce the basicity of bases.
  • Most acids are corrosive, they tend to corrode or rust metals.
  • They produce positive hydrogen ions (H+) when mixed with water.
  • Acids react with metals and form hydrogen gas.
  • Acids produce carbon dioxide when reacted with carbonates.

Introduction to Bases

Bases are substances that substances that are slippery to touch when in aqueous form. Usually, bases taste bitter. They also change the color of red litmus paper to blue. Bases also dissociate in the water like acids, but instead of producing H+ they produce OH- i.e. hydroxyl ion. Alkali is a base which can be dissolved in water. For example, Ammonium Hydroxide, Calcium Hydroxide, etc. Alkalis become less alkaline when mixed with an acid. The pH range of bases is from eight to fourteen.

Some examples are caustic soda or sodium hydroxide, calcium hydroxide or limewater, borax. A lot of bleaches, soaps, detergents, kinds of toothpaste, etc are bases.

Properties Of Bases

The following are the properties of bases :

  • Bases are slippery to touch when in aqueous form.
  • Generally, bases have a bitter taste.
  • Bases produce hydroxyl ions (OH-) when mixed with water.
  • The pH range of bases is from 8 – 14.
  • Bases turn the color of red litmus paper to blue.
  •  Bases lose their basicity when mixed with water.
  • Acids and Bases react to form salt and water.  This process is known as neutralization.

Question For You

Q. What happens when you mix acids and bases?

  1. Neutralization
  2. Endothermic reaction
  3. Exothermic reaction
  4. Evaporation

Sol: The correct option is ‘a’. When acids and bases are mixed, salt and water are formed. This process is known as neutralization. Learn the concept of Neutralization here in detail.

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