Acids, Bases & Salts

Question 1

Acids

• Definition
• Reactions with bases, metals, and carbonates
• Effect on litmus paper, methyl orange and thymolphthalein

Answer 1

Definition: Acids Are Proton Donors (H+)

Reactions:
With Bases:
Acid + Base → Salt + H₂O

With Metals:
Acid + Metal → Salt + H₂

With Carbonates:
Acid + Carbonate → Salt + H₂O + CO₂

Effect on Indicators:
Litmus Paper: blue turns red
Methyl Orange: red to red
Thymolphthalein: colorless to pink

Question 2

Bases

• Bases Vs Alkali
• Definition
• Reactions with Acids & Ammonium salts
• Effect on litmus paper, methyl orange and thymolphthalein

Answer 2

Bases are oxides or hydroxides of metals and alkalis are soluble bases

Bases are proton acceptors (OH-)

Base + Acid -> Salt + H2O
Base + Ammonium Salt -> Salt + Ammonia gas + H2O

Effect on:
Litmus: red litmus turns blue
Methyl Orange: red to yellow
Thymolphthalein: colorless to blue

Question 3

Strong Acid Vs Weak Acid + Examples

Answer 3

A strong acid is an acid that is completely dissociated in aqueous solution.
Hydrochloric acid is a strong acid:
HCl(aq) → H+ (aq) + Cl –(aq)

A Weak acid is an acid that is partially dissociated in aqueous solution.
Ethanoic acid is a weak acid :
CH3COOH(aq) ⇌ H+ (aq) + CH3COO– (aq)

Question 4

Comparing Hydrogen Ion Concentration, Neutrality, Relative Acidity, and Relative Alkalinity with Universal Indicator Paper

Answer 4

• Color:
  Universal indicator paper changes color based on the pH of the solution.
• Neutrality:
  A pH of 7 shows green on universal indicator paper, indicating neutrality.
• Relative Acidity:
  pH values below 7 show colors ranging from red to yellow on universal indicator paper, indicating acidity. Lower pH values indicate stronger acidity.
• Relative Alkalinity:
  pH values above 7 show colors ranging from green to blue on universal indicator paper, indicating alkalinity. Higher pH values indicate stronger alkalinity.

Question 5

Neutralization reaction

Answer 5

Acid and alkali produce water:
H+ (aq) + OH– (aq) → H2O (l)

Question 6

Acidic Oxides

Answer 6

• Typically formed by non-metals.
• React with water to form acidic solutions.
• Examples include SO2 and CO2, which form sulfurous acid and carbonic acid when dissolved in water, respectively.

Question 7

Basic Oxides

Answer 7

• Typically formed by metals.
• React with water to form basic solutions.
• Examples include CuO and CaO, which form copper(II) hydroxide and calcium hydroxide when dissolved in water, respectively.

Question 8

Amphoteric Oxides

Answer 8

Amphoteric oxides exhibit both acidic and basic properties. They can react with both acids and bases to form salts and water.

In acidic conditions, they act as bases, while in basic conditions, they act as acids.

Examples of amphoteric oxides include aluminum oxide (Al₂O₃) and zinc oxide (ZnO).

Question 9

Preparation of salt by:
1. With an Alkali by Titration

2. With Excess Metal
3. With Excess Insoluble Base
4. With Excess Insoluble Carbonate

Answer 9

1. With an Alkali by Titration:
   - Acid is titrated with an alkali until neutralization, forming soluble salt and water.
   - Excess alkali is avoided to prevent contamination.
   - The solution is then evaporated to dryness to obtain pure salt crystals.
2. With Excess Metal:
   - Acid reacts with excess metal to form soluble salt and hydrogen gas.
   - Insoluble impurities are removed by filtration.
   - The solution is then evaporated to dryness to obtain pure salt crystals.
3. With Excess Insoluble Base:
   - Acid is reacted with excess insoluble base, forming soluble salt and water.
   - Insoluble impurities are removed by filtration.
   - The solution is then evaporated to dryness to obtain pure salt crystals.
4. With Excess Insoluble Carbonate:
   - Acid reacts with excess insoluble carbonate, forming soluble salt, carbon dioxide gas, and water.
   - Insoluble impurities are removed by filtration.
   - The solution is then evaporated to dryness to obtain pure salt crystals.

Question 10

General Solubility Rules for Salts

-Sodium, Potassium & Ammonium Salts

• Nitrate Salts
• Chloride Salts
• Sulfate Salts
• Carbonate Salts
• Hydroxide Salts

Answer 10

(a) Sodium, potassium, and ammonium salts are soluble.

(b) Nitrates are soluble.

(c) Chlorides are soluble, except lead and silver.

(d) Sulfates are soluble, except barium, calcium, and lead.

(e) Carbonates are insoluble, except sodium, potassium, and ammonium.

(f) Hydroxides are insoluble, except sodium, potassium, ammonium, and partially calcium.

Question 11

Preparation of Insoluble Salts

Answer 11

The preparation of insoluble salts by precipitation involves:

Mixing solutions of two soluble salts, resulting in the formation of an insoluble salt precipitate.

This precipitate is then filtered and washed to remove impurities, followed by drying to obtain the pure insoluble salt.