Acid, Base, and Salt

Acid: An acid is a chemical species that donates protons or hydrogen ions and/or accepts electrons. ... The word acid comes from the Latin words acidus or acere, which mean "sour," since one of the characteristics of acids in water is a sour taste e.g., vinegar or lemon juice.

Examples: - Hydrochloric acid (HCl), sulphuric acid (H2 SO4), nitric acid (HNO3), carbonic acid ( H2CO3 ) HCl H+   + Cl-

Properties of acids

1. Aqueous solutions of acids are electrolytes, meaning that they conduct electrical currents. Some acids are strong electrolytes because they ionize completely in water, yielding a great many ions. Other acids are weak electrolytes that exist primarily in a non-ionized form when dissolved in water.
2. Acids have a sour taste. Lemons, vinegar, and sour candies all contain acids.
3. Acids change the color of certain acid-base indicates. Two common indicators are litmus and phenolphthalein. Blue litmus turns red in the presence of an acid, while phenolphthalein turns colorless.
4. Acids react with active metals to yield hydrogen gas. Recall that an activity series is a list of metals in descending order of reactivity. Metals that are above hydrogen in the activity series will replace the hydrogen from acid in a single-replacement reaction, shown as Zn(s)+H2SO4(aq)→ZnSO4(aq)+H2(g)
5. Acids react with bases to produce a salt compound and water. When equal moles of an acid and a base are combined, the acid is neutralized by the base. The products of this reaction are an ionic compound, which is labeled as salt, and water.

Uses

1. Carbonic acid is used in soft drinks.
2. Sulphuric acid is used in fertilizers
3. Hydrochloric acid is used for bleaching purposes.
4. Carbolic acid is used as a germ killer.

Base:

In chemistry, a base is a chemical species that donates electrons, accepts protons, or releases hydroxide (OH-) ions in an aqueous solution. Types of bases include Arrhenius base, Bronsted-Lowry base, and Lewis base. Examples of bases include alkali metal hydroxides, alkaline earth metal hydroxides, and soap.

Properties of base

1. Bases change the color of litmus from red to blue.
2. They are bitter in taste.
3. Bases lose their basicity when mixed with acids.
4. Bases react with acids to form salt and water. This process is called Neutralisation Reaction(Read).
5. They can conduct electricity.
6. Bases feel slippery or soapy.
7. Some bases are great conductors of electricity.
8. Bases like sodium hydroxide, potassium hydroxide, etc are used as electrolytes.
9. Alkalis are water-soluble bases. They give hydroxyl ions when dissolved in water. For E.g.: NaOH, KOH and Ca(OH)2.
10. The pH value of bases ranges from 8-14.

Salt:

Salt, in chemistry, the substance produced by the reaction of an acid with a base. A salt consists of the positive ion (cation) of a base and the negative ion (anion) of an acid. The term salt is also used to refer specifically to common table salt, or sodium chloride. They are neutral compounds, which are formed by the reaction between acid and base. Example: NaCl, CaCL2 etc.

Normal salt: The salt formed by the complete displacement of hydrogen atoms by a metal or electropositive radicals. They are neutral in nature. For e.g.: NaCl, KNO3, etc

Strong salt: The salt formed by strong acids and a weak base. E.g. CuSO4

Basic salt: The salt formed by weak acid and strong base. E.g.Ca (HCO3)2

Methods of preparation of salts

They are as follows:

Neutralization of acid and base

NaOH + HCl → NaCl + H2O

Reaction of acid on metallic oxides
FeO + 2HCl → FeCl2 + H2O

Action of acids on metal
Zn + H2SO4 → ZnSO4 + H2

The characteristics of salt are:

1. Common salt (NaCl) is an essential constituent of our diet.
2. Most salts are insoluble in water but few are soluble in water.
3. The solution during the formation of salt the radical derives from acid is called acid radical and the radical obtained from a base is called basic radical. For E.g.: NaOH + H2SO4 → Na2SO4 + H2O

In the salt Na2SO4, sodium radical (Na+) is obtained from the base (NaOH) and SO4--radical is obtained from the acid H2SO4. So Na+ and SO4—are called basic radical and acid radical respectively.

Indicators are the chemical substance used to identify acidic or basic nature of the substance.

Indicator	Acids	Bases
1. Red litmus	remains red	turns blue
2. Blue litmus	turns red	remains blue
3. Phenolphthalein	colourless	pink
4. Methyl orange	red	yellow

A universal indicator is a special kind of indicator which is used to measure the strength of acidity or alkalinity. It is prepared by several organic indicators of different colours. It is found in green-blue solution or in the form of yellow litmus paper.

pH Scale is the scale which shows the number of hydrogen ions in acid or base.
If the concentration of hydrogen ion is less than 7, then it shows acidity of the substance and if the concentration is more than 7 then it shows the basicity of the substance.

When we add alkali on acid, the pH value of the acid goes from its acidic value to value 7 where it acts as a neutral compound as the pH value of neutral compound is 7.