ACIDS, BAASES AND SALTS, ACTIVITY 1 AND ACTIVITY 2, PART1 ENGLISH INDICATORS, OLFACTORY INDICATORS.

Acid – The term acid is derived from the Latin word – ‘Acidus,’ which means ‘sour.’ Acids are any substance in an aqueous solution that tastes sour, changes blue litmus paper to red, and liberates protons. Examples of acidic substances are lemon, orange, grapes, tamarind, etc.

Base – The mild bitter-tasting compounds are bases. Their aqueous solution turns red litmus paper to blue and liberates hydroxide ions. Examples of basic substances are soap, household cleaners.
Acids and Bases Definition
An acid is any hydrogen-containing substance that is capable of donating a proton (hydrogen ion) to another substance. A base is a molecule or ion able to accept a hydrogen ion from an acid.

Acidic substances are usually identified by their sour taste. An acid is basically a molecule which can donate an H+ ion and can remain energetically favorable after a loss of H+. Acids are known to turn blue litmus red.

Bases, on the other hand, are characterized by a bitter taste and a slippery texture. A base that can be dissolved in water is referred to as an alkali. When these substances chemically react with acids, they yield salts. Bases are known to turn red litmus blue.

Acid-Base Indicators in Chemistry
Chemically, indicators are weak organic acids with complex structures. Let’s take a general representation of an indicator.

Types of Acid-Base Indicators
Acid-base indicators are of different types:

Natural Indicators
Artificial Indicators
Olfactory Indicators
1. Natural Indicators
The natural indicator is a naturally occurring substance that can determine whether the substance is acidic or basic. Some examples of natural indicators are given below:

1. Litmus – It is a purple dye that is extracted from a type of algal bloom called ‘lichens’. In an acidic medium, blue litmus paper turns red, and red litmus paper turns blue in a basic or alkaline medium.

2. Turmeric – Turmeric is a common spice present in our kitchen that remains yellow in acidic and neutral solution, but turns bright red when comes in contact with basic solution. In this manner, turmeric behaves as an acid-base indicator.

3. Red cabbage – Red cabbage contains the pigment ‘anthocyanin’, which changes colour when they come into contact with an acid or an alkali. In acidic conditions, it turns red, whereas, in alkaline conditions, it turns green to yellow. In neutral conditions, it remains purple.

4. China Rose – China rose is a natural indicator that turns an acidic solution to dark pink or magenta colour and basic solution to green.

2. Artificial Indicators
Acid-base indicators that are artificially synthesised by using chemicals are known as artificial indicators. Some examples of artificial indicators are given below:

PHENOLPHTHALEIN
It is used as a colorless reagent having a pH range of 8.5, which turns pink to deep red by increasing pH above 9.0.

. Methyl Orange – It is one of the most important and very common azo dye or pH indicators used in acid-base titration in chemical laboratories and also in various industries such as paper, printing, textile industry, etc. Methyl orange turns red in acidic medium and yellow in basic medium.

Bromocresol Blue – Bromocresol Blue (BCG) is a triphenylmethane dye used as a pH indicator. In an alkaline medium, it turns blue and yellow in an acidic medium. In a neutral solution, BCG turns green. Thus, it is mostly used in laboratory applications that require measuring substances that would have a relatively neutral pH (nearly 7). It is commonly used for measuring carbonic acid in a solution.

Eriochrome Black – It is a bluish-black indicator used in complexometric titrations. The most common use of Eriochrome Black is to determine the hardness of the water. As it consists of calcium carbonate, when all calcium is dissolved in water during titration, the indicator shows an electric blue colour

3. Olfactory Indicators
The substances whose odour varies in the acidic and basic medium are known as olfactory indicators. Such indicators are very useful for visually impaired students to detect acid and base in chemical laboratories as they cannot see the colour change. Some examples of olfactory indicators are given below:

Vanilla Essence – In an acidic medium, vanilla essence retains its smell but loses it in basic medium. This helps to identify whether a substance is acidic or basic in nature.

2. Onion – In acidic medium onion retains its smell but loses it in basic medium—this helps to identify whether a substance is acidic or basic.

3. Clove oil – It smells as such in an acidic medium, but the smell of clove oil disappears in basic medium.

Видео ACIDS, BAASES AND SALTS, ACTIVITY 1 AND ACTIVITY 2, PART1 ENGLISH INDICATORS, OLFACTORY INDICATORS. канала kushi physics