Acid and Base salts

An Acid has the capability to donate a proton or a hydrogen ion and form a covalent bond with an electron pair. Examples of acids are hydrochloric acid and acetic acid.

 

A base has the capability to release hydroxide ions. If a base is soluble in water then it is called an alkali. Bases exhibit properties such as bitter taste and soapy feel. Examples of bases are sodium hydroxide and ammonia.

 

When acids are dissolved in water, they increase the concentration of hydronium ions. When bases are dissolved in water they increase the concentration of hydroxide ions.

 

The pH Scale

The pH scale is used to measure the extent to which a given solution is acidic or alkaline. This scale runs from pH0 to pH14. A pH value of 7 means the solution is neutral. The solution is acidic if it has a pH value less than 7 and alkaline if it has a pH value greater than 7.

 

Examples of acids and bases with molecular formulae

Acids:

Sulphuric acid (H2SO4), Hydrochloric acid (HCl), Nitric acid (HNO3), Chloric acid (HClO3)

Bases:

Sodium hydroxide (NaOH), Potassium hydroxide (KOH), Calcium hydroxide (Ca(OH)2)

 

  • Acids can cause blisters and burns on the skin so you should be careful while handling acids. Some bases can also irritate the skin.
  • Bases are commonly used in the manufacture of bleaching powder, soaps and household cleaners.

 

Acid and base reaction

When an acid is mixed with a base, a chemical reaction takes place and salt and water are produced. This is termed a neutralization reaction. The word equation can be written as:

 

Acid + Base → Salt + Water

 

Naming convention

The resultant salt formed is named in two parts. The first part is taken from the metal component in the base and the second part is derived from the acid used in the reaction. For hydrochloric acid the second name used is chloride, for sulphuric acid it is sulphate and for nitric acid it is nitrate.

 

For example: Consider the reaction when Sulphuric acid and sodium hydroxide react to form salt and water.

 

H2SO4 + 2NaOH → Na2SO4 + 2H2O

 

The products formed are sodium sulphate and water. In the above example the metal in the base is sodium and the acid is sulphuric acid and hence the name sodium sulphate.

 

For example: Sodium hydroxide and hydrochloric acid react to form salt and water.

 

HCl + NaOH →  NaCl + H2O

 

The salt formed is Sodium chloride.

 

For example: Nitric acid reacts with sodium hydroxide to form salt and water.

 

HNO3 + NaOH → NaNO3 +  H2O

 

The salt formed is Sodium nitrate.

 

  • You can find out whether the solution is acidic or alkaline using a litmus paper test. There are red and blue litmus papers that are used to test the presence of acids and bases.

Litmus paper turns purple in neutral solutions. When you dip blue litmus paper in an acidic solution it turns red. When you dip a red litmus paper in an alkaline solution it turns blue.

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