Acids

DEFINITION:-

Substances that ionize (break off) in an aqueous solution to produce hydrogen (H+) ions are known as Acids and the substances that ionize in an aqueous solution to produce hydroxide (OH-) ions are known as Bases.

Salts:-

Salts in chemistry is a substance produced by the neutralization reaction of an acid with a base. A salt is a compound composed of two ions, a positively charged ion and a negatively charged ion. The attraction between the two ions forms strong ionic bonds, giving salts a hard and brittle crystalline structure.

The process where acids and bases neutralize each other to form salt and water is known as neutralization.

GENERAL PROPERTIES:-

ACIDS:-

• Acid is a compound which yields hydrogen ion (H+), when dissolved in water.
  HCl + H₂O → H⁺+ Cl⁻
• Acid is sour to the taste and it is corrosive in nature. The pH of acids is less than 7.
• All acids react with metal to release hydrogen gas. For example, zinc metal reacts with hydrochloric acid to form zinc chloride and hydrogen gas.
  Zn + 2HCl → ZnCl₂ + H₂
• When acids react with limestone (CaCO₃), it produces carbon dioxide. For example, HCl reacts with limestone to produce carbonic acid and calcium chloride.
  CaCO₃+2HCl→CaCl₂+CO₂+H₂O
• Acids are classified into organic and inorganic acids. The best example of organic acid is acetic acid (CH₃COOH), and inorganic acids are those which are produced from minerals; for example, sulphuric acid (H₂SO₄), and hydrochloric acid. Etc.
• Acid usually converts blue litmus paper to red litmus paper.

• Acids have a tendency to quickly corrode the metal surfaces.
• Some Acids are highly corrosive in nature.
• In Acidic solution Methyl orange gives Red colour.
• Acids turn the pink colour of Phenolphthalein to colourless.

Examples:- Lemons, oranges, vinegar, sulfuric acid, hydrochloric acid.

Uses:- Benzoic acid (salt used to preserve food),

Carbonic acid- Used to make carbonated drinks. 

Ethanoic acid- Used to clean metals before electroplating/processing leather/household cleaning/ maintenance of swimming pools.

Sulphuric acid- To make fertilizers, polymer, and detergent

Strong acids: These acids get completely (100%) ionized in the aqueous solutions. Thus, at equilibrium, the concentration of acid molecules becomes very less and concentration of hydrogen ion reaches to the maximum; for example, HCL, HNO₃, HClO₄

Weak acids: These acids are only partially ionized in solution at equilibrium state. At equilibrium state, molecules of acid are present in a considerable amount and the concentration of hydrogen ion is less, for example, HF, CH₃COOH

BASES:-

• Bases are compounds which yields hydroxide ion (OH⁻), when it is dissolved in water.
• Bases are bitter in taste and are corrosive in nature. They usually feel slippery and very soapy.
• Bases are good conductor of electricity and usually shows a pH value of more than 7.
• Bases react with oils and grease to form molecules of soap.
• Bases convert red litmus paper to blue litmus paper.

• In Basic solution Methyl orange gives Yellow colour
• Phenolphthalein solution turns pink in the presence of a base

Examples:- Soap, toothpaste, bleach, cleaning agents, lime water, ammonia water, sodium hydroxide.

Uses:-

Ammonia- Used in the production of fertilizers, used in manufacturing of nitric acid, to prevent clotting in natural and synthetic latex.

Aluminium hydroxide- Often used to make gastric medicine-antacid.,

Calcium hydroxide- Used to make cement, lime water, help with application of sewage treatment, and neutralize soil's acidity.

Strong bases: These are the bases which are completely ionized in water to produce hydroxide ions, e.g., sodium hydroxide.

NaOH_(s) ⇌ Na⁺_(aq) + OH⁻_(aq)

Weak bases: These are the bases which are partially ionized and the equilibrium lies mostly towards the reactants side, e.g., ammonia in water.

NH_3(aq) + H₂O_(l) ⇌ NH4⁺_(aq) + OH⁻_(aq)

SALTS:-

• Salts are ionic in nature due to the presence of ions.
• They are brittle, hard and crystalline solids.
• Salt is white, odourless and it has a salty taste.
• All potassium (K), ammonium (NH₄⁺) and sodium (Na) salts are soluble in water (H₂O).
• Sodium Chloride(NaCl) generally known as ‘Common salt’ or ‘Table salt’ is used in our day to day life.

Examples:- Copper Sulfate, Sodium Bisulfate, Calcium Chloride, Potassium Dichromate, Sodium Chloride