Acids, bases and salts

Introduction

Almost every substance that we use in our day to day life could be acidic or alkaline. This depends upon the pH level, taste, colour, nature and the way a particular substance interact with other substance. Why do substances vary in their taste, colour, and nature? Tamarind and lemon taste similar whereas salt tastes different, why? This is because of variation in the percentage of acids, bases, and salts in their chemical composition. In our daily life, many consumer products such as milk, juices, soaps, and snacks contain these substances making them taste as they are. In the past, acid, base, salt were defined based on their taste but the experimental definitions have been developed recently to define them based on their chemical nature and the taste.

 

Table Of Contents

1. Introduction

2. Definitions

3. Some naturally occurring acids and bases

4. Differences between acids and bases

 

Definitions

1. “An acid is defined as a substance whose water solution tastes sour and when blue litmus is dipped, it will turn into red”.  

2. “A base or an alkali is characterized by its aqueous solution tastes bitter and turns red litmus into blue or it has an ability to neutralize acids to give salt and water”.

3. “A salt is a neutral substance whose aqueous solution does not affect the litmus”.

 

Some naturally occurring acids and bases

1. Acetic acid (CH3CO2H); is produced through bacterial fermentation used in the production of vinegar and also as a solvent.

2. The citric acid (C6H8O7) is a part of citrus fruit used in food preservation and flavouring.

3. Formic acid (HCOOH) can be found in the stings of ants and bees. It is used for a variety of purposes such as esterification and as a preservative.

4. Lactic acid (C3H6O3): It is released by muscles during exercise and also it’s a part of certain milk products such as yoghurt and cheeses.

5. Ammonia (NH3): Certain organisms produce ammonia from atmospheric nitrogen. It is useful as household cleaners, and also as part of many fertilizers.

6. Potassium hydroxide (KOH): Leaching of certain wood ashes was known historically to produce potash. This can be used to produce soap as well as fertilizer.

7. Sodium bicarbonate NaHCO3: It is produced naturally from a mineral known as nahcolite. It is useful for various pest control purposes and antacids. It helps the dough or batter to expand.

 

Differences between acids and bases

Acids

Bases

Acids taste sour

Bases are bitter in taste

An acid turns blue litmus into red color.

A base turns red litmus into blue color.

An ideal example of an acid is Hydrochloric acid HCl.

The most commonly found base is  Sodium hydroxide NaOH.

The strength of an acid Relies on the concentration of the hydrogen ions.

The strength of the base depends upon the concentration of the hydroxide ions.

The characteristics of an acid depending upon the temperature. They might look solid, liquid or in the form of gas.

These may feel slippery and solid in nature with an exception being ammonia as it is gaseous.

When it comes to dissociation, Acids would release hydrogen ions (h+) when mixed with water.

The dissociation in the base is characterized by the release of hydroxide ions(OH-) when mixed with water.

pH of acid is less than 7

pH of a base is more than 7

Acids when dissolved in water doesn’t cause any change in the color of water

When bases are dissolved in water, the water turns pink.

Common examples:  Hydrochloric acid (HCl), Sulphuric acid (H2SO4), Nitric acid (HNO3), Carbonic acid (H2CO3).       

Examples: Ammonium hydroxide (NH4OH), Calcium hydroxide (Ca(OH)2), Sodium hydroxide (NaOH).

 

 

Acid-Base Indicator:

Acid-Base indicators are also known as pH indicators.  Acid-base indicators are weak acids or bases, which when dissolved in water dissociate slightly to form ions.

Name of the Indicator

If you mix acid

If you mix base

Blue litmus solution

Turns to red

No change

Red litmus solution

No change

Turns to blue

Turmeric

No change

Turns to red

Methyl orange

Turns to red

Turns to yellow

Phenolphthalein (colourless)

No change

Turns to pink

 

Salts

Salts are neutral in nature. A salt is formed when acids and bases combine together. A salt contains cations(+) and anions(-) in an equal proportion. In its natural form, salt can be crystalline or amorphous. Salts contain two groups of ions with a positively charged  (H+) and negatively charged (OH-). In our day to day life, there are a lot of items that we use as salts. The chemical formula of common salt is NaCl ( Sodium Chloride). The pH of salt is neutral -7, that is neither acidic nor basic.





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