class 7 acid and bases

An acid is a substance that donates hydrogen ions (H⁺) and has a sour taste.

The word 'acid' comes from the Latin word 'acere' meaning sour.

Substances that contain acids are known as acidic substances.

Organic acids are acids that are naturally obtained from plants and animal sources.

Mineral acids, also known as inorganic acids, are acids derived from inorganic material or sources.

Examples of mineral acids include nitric acid, hydrochloric acid, and sulfuric acid.

Concentrated acids contain only a small quantity of water.

Dilute acids contain more water than concentrated acids.

Dilute acids can be obtained by adding water to a concentrated acid.

Acids are sour to taste, turn blue litmus red, turn methyl orange red, turn phenolphthalein colorless, can corrode metals, are soluble in water, react with metals to form salt and hydrogen gas, react with bases to form salt and water, and react with carbonates to form salt and carbon dioxide gas.

Acids react with metals to form a salt and hydrogen gas.

Acids react with bases to form a salt and water.

Acids react with carbonates to form a salt and carbon dioxide gas.

Examples of strong acids include hydrochloric acid, sulfuric acid, nitric acid, and phosphoric acid.

Examples of weak acids include citric acid, lactic acid, acetic acid, and carbonic acid.

Hydrochloric acid is present in the stomach and helps in the digestion of food.

A base is a chemical substance that is bitter in taste and soapy to touch.

Substances that contain bases are known as basic substances.

An alkali is a base that is soluble in water.

Examples of strong bases include sodium hydroxide and potassium hydroxide.

Examples of weak bases include ammonium hydroxide and calcium hydroxide.

Bases are bitter to taste, turn red litmus blue, feel soapy to touch, react with acids to form salt and water, and are soluble in water.

Blue litmus turns red in an acid.

Red litmus turns blue in a base.

Neutralization is the reaction between an acid and a base to produce salt and water.

An example of a neutralization reaction is hydrochloric acid (HCl) reacting with sodium hydroxide (NaOH) to form sodium chloride (NaCl) and water (H₂O).

The pH scale measures how acidic or basic a substance is, ranging from 0 to 14.

The pH range for acids is less than 7.

The pH range for bases is greater than 7.

The neutral pH value is 7.

Litmus paper is an indicator used to test whether a substance is acidic or basic.

Phenolphthalein is an indicator that turns colorless in acid and pink in base.

Methyl orange is an indicator that turns red in acid and yellow in base.

Acids are used in the industry and are present in products like vinegar (acetic acid) and citrus fruits (citric acid).

Baking soda is a common household substance with sodium bicarbonate (NaHCO₃) as its main base.

Antacids are substances used to neutralize excess stomach acid.

Bases in cleaning products neutralize acids and break down grease.

Neutralization is the reaction between an acid and a base to produce salt and water.

An example is hydrochloric acid (HCl) reacting with sodium hydroxide (NaOH) to form sodium chloride (NaCl) and water (H₂O).

HCl + NaOH → NaCl + H₂O

The pH value of a neutral solution is 7.

Neutralization is important in various everyday applications, such as in antacids to relieve indigestion and in agriculture to neutralize acidic soils.

Neutralization with lime (calcium oxide) helps to reduce the acidity of soils, making them more suitable for farming.

Bases generally do not react with metals like acids do.

An indicator is a substance that changes color to indicate whether a solution is acidic or basic.

Indicators help to determine the pH of a solution by changing color in acidic or basic environments.

Litmus, obtained from lichens, is an example of a natural indicator.

Phenolphthalein turns pink in a basic solution.

Phenolphthalein remains colorless in an acidic solution.

Methyl orange turns yellow in a basic solution.

Methyl orange turns red in an acidic solution.

Acids are used in industries for manufacturing fertilizers, dyes, and explosives.

Bases are used in industries for making soap, paper, and textiles.

An antacid is a substance used to neutralize excess stomach acid, providing relief from indigestion.

Baking soda (sodium bicarbonate) acts as a base by neutralizing acids and is commonly used in cooking and cleaning.

Acids in food contribute to its sour taste and act as preservatives.

Bases help in cleaning products by neutralizing acids and breaking down grease.

A common base found in household cleaning products is ammonia (ammonium hydroxide).

The pH of lemon juice, which contains citric acid, is around 2-3.

The pH of soap, which is basic, is around 9-10.

Acids and bases can be corrosive and cause burns or other injuries, so it is important to handle them with care and use appropriate safety measures.