Acid, base and salt

 Acids

Definition: Substances containing an acid (from Latin "acere" meaning sour)

Types: Mineral acids and organic acids

Mineral Acids

Examples: 

Hydrochloric acid (HCI),

sulphuric acid (H2SO4), and nitric acid (HNO3)

Uses: Laboratory, industrial applications

Properties: Strong, corrosive, and highly reactive towards metals

Organic Acids

Examples: Tartaric acid (grapes), acetic

acid (vinegar), formic acid (sting of ants and bees), malic acid (apples), citric acid (lemons and oranges), lactic acid (milk)

Properties: Weak, naturally occurring in animal and plant materials

Strong and Weak Acids

Strong acids: Highly corrosive, mineral

acids (e.g., hydrochloric acid, sulphuric acid, and nitric acid)

Weak acids: Less destructive, mostly organic acids (e.g., acetic acid)

Properties of Acids

Sour taste

Corrosive nature

Soluble in water

Can be dilute or concentrated

Uses of Acids

Hydrochloric acid (HCI):

Used in industries for heating applications

Cleaning sinks and sanitary ware

Sulphuric acid (H2SO4):

Used in car batteries

Manufacture of paints, drugs, dyes, and fertilizers

Nitric acid (HNO3):

Used by goldsmiths for cleaning gold and silver ornaments

Production of fertilizers

Acetic acid (CH3COOH):

Main ingredient of vinegar

Enhances flavor of food and acts as a preservative in pickles

Used as a cleansing agent

Acidic Environment and Microorganisms

Most microorganisms cannot live in an acidic environment.

Acidic environment can slow down or kill microorganisms.

This is why vinegar is used in many packaged food items like pickles, sauce, and ketchups.

Acid Rain

Acid rain is a major effect of air pollution.

Pollutants like sulphur dioxide and oxides of nitrogen react with atmospheric water and oxygen to form sulphuric acid and nitric acid.

Acid rain can damage plant and animal life, buildings, and monuments.

True or False Statements

1. Acids can be stored in metal containers: False (Acids are corrosive and can react with metals.)

2. Mineral acids are present in animal and plant materials: False (Mineral acids are produced from chemical substances, whereas organic acids are present in animal and plant materials.)

3. A dilute acid has more amount of water than a concentrated acid: True

4. Sulphuric acid is used for cleaning sinks and sanitary ware: False (Hydrochloric acid is used for cleaning sinks and sanitary ware.)

5. Nitric acid is used by goldsmiths for cleaning gold and silver ornaments: True

6. Hydrochloric acid is used to enhance the flavor of food and as a preservative in pickles: False (Acetic acid is used to enhance the flavor of food and as a preservative in pickles.)

Fill in the Blanks

1. Acids are sour to taste.

2. Apples contain malic acid, whereas spinach has oxalic acid.

3. Strong acids are highly corrosive.

4. Organic acids are weak acids.

5. Carbonic acid is present in fizzy drinks and soda water.

Bases

Definition: Substances containing a base are called basic substances.

Examples: Sodium hydroxide (NaOH), calcium hydroxide (Ca(OH)2)

Properties: Bitter taste, slippery feel, may or may not be soluble in water

Strong and Weak Bases

Strong bases: Highly corrosive, can burn skin (e.g., sodium hydroxide, potassium hydroxide)

Weak bases: Less corrosive (e.g., copper hydroxide, zinc hydroxide, ammonium hydroxide)

Uses of Bases

Calcium hydroxide (slaked lime):

Neutralizes acidity in soils

Used in whitewash and mortar

Used in Bordeaux mixture for protecting crops

Magnesium hydroxide (milk of magnesia):

Used as an antacid or laxative

Corrects excess acidity in the stomach

Sodium hydroxide (caustic soda):

Used in manufacture of paper and textiles

Used to unblock drains

Used in manufacture of soaps and detergents

Indicators

Definition: Substances that show a

change in color when brought in contact with acids and bases.

Examples: Litmus, phenolphthalein,

methyl orange

Types: Natural indicators (e.g., turmeric, red cabbage), universal indicators (e.g pH paper)

pH and Universal Indicators

pH: A measure of the strength of an acid or base, ranging from 1 to 14.

Universal indicator: A mixture of indicators that gives a different color for different pH values.

pH paper: A paper soaked in universal indicator solution.

A. Fill in the blanks

1. Strong acids are highly corrosive and can cause severe burns.

2. Bases are slippery to touch.

3. Sulphuric acid is used in the manufacture of paints, dyes, and drugs.

4. Sodium hydroxide is used to unblock drains.

5. Blue litmus changes to red in acids.

B. Choose the correct option

1. d. Sulphuric acid is called the "King of chemicals".

2. c. Acetic acid is present in vinegar.

3. a. Carbonic acid is a weak mineral acid.

4. b. Calamine lotion is used to neutralize bee stings.

5. c. Sugar cannot be used as an indicator.

6. d. Both Potash alum and Silver nitrate are salts.

7. b. Hydrochloric acid is used to remove deposits from the inside of boilers.

8. c. KOH is a strong base.

9. d. pH = 13 represents a strong alkali.

10. a. High melting point is a characteristic property of most salts.

Matching

1. CH3COOH - c. Acetic acid

2. AgNO3 a. Silver nitrate

3. NH4NO3 d. Ammonium nitrate

4. Ca(OH)2 - e. Calcium hydroxide

5. CaCO3 b. Calcium carbonate

Very Short Answer Type Questions

1. Alkalis

2. Indicator

3. pH paper

4. Neutral salt

5. Hydrated salts

Short Answer Type Questions

1. Properties of acids: Sour taste, corrosive nature

Properties of bases:

 Bitter taste, slippery feel

2. Acids or bases are added to soil to adjust its pH for optimal plant growth.

3. Neutralization reaction: A reaction between an acid and a base to form a salt and water. Example: HCI + NaOH NaCl + H2O

4. A hydrated salt can be converted into an anhydrous salt by heating it to remove the water of crystallization. Example: CuSO4.5H20 CuSO4 + 5H2O ←

Long Answer Type Questions

1. Natural indicators can be prepared from plant materials like flowers, roots, stems, and leaves. 

Examples:

Flower: Rose petals

Root: Beetroot

Stem: Turmeric

Leaf: Red cabbage

Red cabbage juice shows different colors in acidic, neutral, and basic mediums: deep red in acidic, purple in neutral, and green/yellow in basic.

2. a. Vinegar is used in packaged food items as a preservative.

b. Slaked lime is added to factory waste to neutralize acidic substances.

c. Magnesium hydroxide is used as an antacid to neutralize excess acid in the stomach.

d. Strong acids and bases should be handled carefully because they can cause severe burns and damage.

3. Water of crystallization: Water molecules present in the crystal structure of a salt. Example: CuSO4-5H2O (copper sulfate pentahydrate

Let's Observe

1. a. Food items: Not specified

b. Process: Not specified

c. Chemical used: Not specified

2. Acidic solution: Turns blue litmus

paper red

Basic solution: Turns red litmus paper blue

Let's Apply

1. Pickles and sauces are not packaged in metal containers because the preservative used (acidic substance) can react with the metal.

2. Hydrochloric acid in the stomach does not corrode the stomach lining because it is highly concentrated and the stomach lining has a protective mechanism.)

Let's Analyse and Evaluate

1. The sanitary ware cleaner likely contained an acidic substance that reacted with the marble flooring, causing discoloration.

2. The cleaner does not spoil sinks and sanitary ware because they are made of materials that can withstand acidic substances, but marble is more sensitive to acidic reactions.