Acids, Bases and Alkali

Question 1

What is an acid?

Answer 1

A substance that releases hydrogen ions (H⁺) when dissolved in water.

Examples: HCl, H₂SO₄, HNO₃. pH: Less than 7.

Question 2

What is a base?

Answer 2

A substance that can neutralize an acid to form a salt and water.

Examples: Metal oxides (e.g., CuO), metal hydroxides (e.g., NaOH), and ammonia (NH₃).

Question 3

What is an alkali?

Answer 3

A base that dissolves in water to release hydroxide ions (OH⁻).

Examples: NaOH, KOH, NH₃ (aqueous). pH: Greater than 7.

Question 4

What is a salt?

Answer 4

A compound formed when the hydrogen ion of an acid is replaced by a metal ion or ammonium ion (NH₄⁺).

Examples: NaCl (sodium chloride), CuSO₄ (copper(II) sulfate).

Question 5

What are the properties of acids?

Answer 5

Sour taste, turn blue litmus red, react with metals, bases, and carbonates to form salts.

Question 6

What is the reaction of an acid with a metal?

Answer 6

Acid + Metal → Salt + Hydrogen.

Example: 2HCl + Mg → MgCl₂ + H₂.

Question 7

What is the reaction of an acid with a base?

Answer 7

Acid + Base → Salt + Water (Neutralization).

Example: H₂SO₄ + 2NaOH → Na₂SO₄ + 2H₂O.

Question 8

What is the reaction of an acid with a carbonate?

Answer 8

Acid + Carbonate → Salt + Water + Carbon Dioxide.

Example: 2HCl + CaCO₃ → CaCl₂ + H₂O + CO₂.

Question 9

What is the reaction of an acid with ammonia?

Answer 9

Acid + Ammonia → Ammonium Salt.

Example: HCl + NH₃ → NH₄Cl.

Question 10

What are the properties of bases/alkalis?

Answer 10

Bases neutralize acids, alkalis are soluble bases, turn red litmus blue, have a slippery feel.

Question 11

What is the reaction of an alkali with an acid?

Answer 11

Alkali + Acid → Salt + Water (Neutralization).

Example: NaOH + HNO₃ → NaNO₃ + H₂O.

Question 12

What is the reaction of an alkali with an ammonium salt?

Answer 12

Alkali + Ammonium Salt → Salt + Ammonia + Water.

Example: NaOH + NH₄Cl → NaCl + NH₃ + H₂O.

Question 13

What is the reaction of an alkali with a metal ion solution?

Answer 13

Alkali + Metal Ion Solution → Precipitate.

Example: CuSO₄ + 2NaOH → Cu(OH)₂↓ + Na₂SO₄.

Question 14

What is neutralization?

Answer 14

Combining H⁺ ions from the acid with OH⁻ ions from the alkali to form water.

Example: H⁺ + OH⁻ → H₂O.

Question 15

What does the pH scale indicate?

Answer 15

pH < 7: Acidic, pH = 7: Neutral, pH > 7: Alkaline.

Question 16

What is the litmus indicator?

Answer 16

Red in acid, blue in alkali.

Question 17

What is the methyl orange indicator?

Answer 17

Red in acid, yellow in alkali.

Question 18

What is the phenolphthalein indicator?

Answer 18

Colorless in acid, pink in alkali.

Question 19

What is the universal indicator?

Answer 19

A range of colors showing different pH levels.

Question 20

How are salts prepared?

Answer 20

By reacting an acid with metals, insoluble bases, carbonates, or alkalis.

Question 21

What is the method of salt preparation using a metal?

Answer 21

Add excess metal to acid until bubbling stops, filter, and evaporate the solution.

Example: Zn + 2HCl → ZnCl₂ + H₂.

Question 22

What is the method of salt preparation using an insoluble base?

Answer 22

Warm the acid, add excess base, filter, and evaporate water.

Example: CuO + H₂SO₄ → CuSO₄ + H₂O.

Question 23

What is the method of salt preparation using a carbonate?

Answer 23

Add carbonate to acid until no more fizzing occurs, filter, and crystallize the salt.

Example: CaCO₃ + 2HCl → CaCl₂ + H₂O + CO₂.

Question 24

What is the titration method for salt preparation?

Answer 24

Use a pipette to measure alkali, add acid from a burette, and crystallize the salt.

Example: HCl + NaOH → NaCl + H₂O.

Question 25

What are the solubility rules for salts?

Answer 25

Soluble: Sodium, potassium, ammonium salts, all nitrates, chlorides (except AgCl, PbCl₂), sulfates (except BaSO₄, PbSO₄, CaSO₄). Insoluble: Carbonates (except Na⁺, K⁺, NH₄⁺), hydroxides (except Na⁺, K⁺, NH₄⁺).

Question 26

What are precipitation reactions?

Answer 26

Used to prepare insoluble salts by mixing two soluble salts.

Example: React barium chloride with sodium sulfate to form barium sulfate precipitate.