ACIDS, BASES AND SALTS

Acids – Acids are the substances which are sour in taste and change blue litmus to red.

Bases – Bases are the substances which are bitter in taste and change red litmus to blue.

Neutralization – The reaction of acids with base to form salt and water is termed as neutralization. In this process acid is neutralized by base and vice versa.

Indicators – Indicators are the substances that change their color or odour when added to acid or base and indicate the presence of acid or base.

Natural Indicators – These are the indicators found in nature in plants. Eg. Red cabbage, turmeric.

Synthetic Indicators – These indicators are synthesized in the laboratory or industry. Eg. Methyl orange, phenolphthalein

Olfactory Indicators – The substances whose odour changes in acidic or basic solution are called as Olfactory Indicators. Eg. Vanilla extract, Onion

Universal Indicators – This is the mixture of several indicators.

pH Scale (Potenz Scale) – This is the scale used to measure the concentration of Hydrogen ions in the solution.

Brine solution – Aqueous solution of Sodium Chloride is called Brine solution.

Chlor-Alkali Process – Passing of electric current through aqueous solution of sodium chloride (brine) to form chlorine and alkali is called Chlor-Alkali process.

Water of crystallization – Crystals of some compounds appears to be dry but contains some water molecules attached to them. These water molecules are called as “Water of crystallization”

Antacid – Medicines used to reduce the effect of acid are called as Antacids (Eg. Milk of Magnesia)

Acid Rain – If pH of the rain water is less than 5.6 then it is called as Acid Rain.

Change of color of Indicators in Acids and Bases

	ACIDS	BASES
Taste	Sour	Bitter
Litmus	Blue to Red	Red to Blue
Phenolphthalein	Colourless	Pink
Methyl Orange	Red	Yellow
Examples	HCl, H2SO4	NaOH, KOH

 Give reasons

 1)    Lime water turns milky when CO₂ is passed through it

When CO₂ is passed through lime water, While precipitate of calcium carbonate is formed. This turns the lime water milky.

 

2)    Water should not be added to concentrated acid

If water is added to concentrated acid, large amount of heat is generated. This reaction is highly exothermic. The solution may splash out causing burns to the person nearby.

 

3)    Antacid is given to the person suffering from acidity

Stomach produces more acid sometimes. This leads to the problem called acidity. Antacids which are basic in nature helps to neutralize the acid in stomach.

 

4)    Tooth paste are basic in nature

If the food particles remain in mouth, bacteria start degrading it and acid is produced in this process. If the pH level goes below 5.5, decay of tooth enamel begins. Toothpaste which is basic in nature helps to neutralize the acid and prevents tooth decay.

 

5)    Baking soda is applied on the area affected by bee or ant sting

When insect like honey bee or ant bite, they inject methanoic acid. This is bit painful. To neutralize the effect of acid baking soda which is basic in nature is applied on affected area.

 

6)    Electrolysis of Brine is called as Chlor-Alkali process

In this the products formed are Chlorine and alkali (Sodium hydroxide). So it is called as Chlor-alkali process.

 

7)    Baking powder makes the bread and cake spongy

Baking soda is the major ingredient of Baking powder. Baking soda when heated produces CO₂. This make the bread and cake spongy.

  

Source	Acid
Curd	Lactic Acid
Lemon	Citric Acid
Tamarind	Tartaric Acid
Tomato	Oxalic Acid
Ant sting	Methanoic Acid
Vinegar	Acetic Acid