Haryana State Board HBSE 10th Class Science Notes Chapter 2 Acids, Bases and Salts Notes.
Haryana Board 10th Class Science Notes Chapter 2 Acids, Bases and Salts
Understanding chemical Properties of Acids and Bases:
- In present times, 114 elements are known to us. These elements combine in several ways and give rise to a very large number of compounds.
- On the basis of their chemical properties all the compounds is can be divided into three groups. They are:
Acids: An acid is a compound having hydrogen which when dissolved in water releases i.e. dissociates hydrogen ions (H+) to be specific (H3O+ ions). For example, hydrochloric acid (HCl), sulphuric acid (H2SO4), etc.
Bases: A base is a metal hydroxide substance which when dissolved in water release hydroxide (OH–) ions. For example, sodium hydroxide (NaOH), calcium hydroxide (Ca(OH)2), etc.
Salts: A salt is an ionic compound which is formed from the neutralization reaction of an acid and a base.
Olfactory Indicators: Olfactory means ‘relating to the sense of smell’. Those substances whose smell changes in acidic or basic solutions are called olfactory indicators.
Outcomes of certain important types of reactions:
Reaction of acid with metal:
When acid reacts with metal, metallic salt of that metal and hydrogen gas are produced.
Reaction of base with metal:
When a strong base reacts with certain metals, it produces salt and hydrogen gas.
Reaction of acid with metal carbonate or metal hydrogen carbonate:
When acids react with metal carbonate or metal hydrogen carbonate, most acids produce salt, water and carbon dioxide gas.
Reaction of acid with base:
When acid reacts with base, salt and water are produced. Since base neutralizes the effect of acid, this reaction is called neutralization reaction.
Reaction of acid with metal oxide:
When acid reacts with metal oxide, salt and water are produced.
Reaction of nonmetallic oxide with base:
When a non-metallic oxide reacts with base, the reaction gives out salt and water.
How Strong are Acid or Base Solutions?
An acid which gets completely ionized completely in water or say which completely dissociates in water and produce a large amount of hydrogen [H+] ions (or say hydronium [H2O+] ions) is called a strong acid.
An acid which does not ionize completely (i.e. does not dissociate completely in water) and thus produce a small amount of hydrogen [H+] ions (or say H2O+ ions) is called a weak acid.
A base, which completely ionizes in water and thus produces a large amount of hydroxide (OH–) ions, is called a strong base or a strong alkali.
A base, which does not ionize completely in water and thus produces a small amount of hydroxide (OH–) ions, is called a weak base or a weak alkali.
The methods of measuring the strength of an acid or a base:
- Through universal indicator and
- Through pH scale
- The pH scale measures concentration of hydrogen [H+] ions in the solution.
- The scale points range from O to 14. 0 means very acidic and 14 means very alkaline. Scale point 7 means neutral solution.
Importance of pH in everyday life:
- Importance of pH in existence of living beings,
- Importance of pH in soil,
- Importance of pH in digestion of food,
- Importance of pH in stopping tooth decay,
- Self-defence by animals and plats through Chemical warfare:
More About Salts
- A salt is an ionic compound which is formed by the neutralization reaction of an acid and a base. Thus, we get salt when we react an acid with a base. When we dissolve a salt in water it will get ionized and release cation (i.e. the positive +ve ion) and anion (i.e. the negative – ve ion).
- In general, salts having same type of cations (+ve ions) or anions (-ve) belong to the same family.
Some Important Salts: