What are the main methods to prepare salts?

The main methods include reaction of acids with metals, metal oxides, carbonates, neutralization with bases, direct combination of elements, and double displacement reactions.

Which gas is released when acids react with carbonates?

Carbon dioxide (CO2) is released when acids react with carbonates.

How can we obtain pure salt crystals?

Evaporate water from a salt solution to obtain pure crystals, a process called crystallization.

Preparation of Salts

Chemists prepare salts by reacting acids with bases, metals, or carbonates. Depending on the reactants, they apply different methods to produce salts effectively. Below, we explain the six main methods, with examples and reactions.Preparation of Salts

1. Reaction of Acids with Metals

Reactive metals such as zinc, magnesium, and iron react directly with dilute acids to produce salts and hydrogen gas. For example, zinc reacts with sulfuric acid to form zinc sulfate and hydrogen. Learn more.

Zn (s) + H₂SO₄ (aq) → ZnSO₄ (aq) + H₂ (g)

2. Reaction of Acids with Metal Oxides

Acids react with basic metal oxides to form salts and water. For instance, copper oxide reacts with sulfuric acid to yield copper sulfate. Reference.

CuO (s) + H₂SO₄ (aq) → CuSO₄ (aq) + H₂O (l)

3. Reaction of Acids with Metal Carbonates

When acids react with metal carbonates, they produce salts, carbon dioxide, and water. This method is common in laboratories for preparing salts. More examples.

CaCO₃ (s) + 2HCl (aq) → CaCl₂ (aq) + CO₂ (g) + H₂O (l)

4. Neutralization Reaction (Acid + Base)

Mixing an acid with a base forms salt and water. For example, hydrochloric acid reacts with sodium hydroxide to produce sodium chloride. Read more.

NaOH (aq) + HCl (aq) → NaCl (aq) + H₂O (l)

5. Direct Combination of Elements

Some salts form by directly combining their elements. For instance, sodium reacts with chlorine to produce sodium chloride.

2Na (s) + Cl₂ (g) → 2NaCl (s)

6. Double Displacement (Precipitation) Reactions

Mix two solutions containing different ions. They produce a soluble and an insoluble salt. The insoluble salt precipitates out. For example, mixing silver nitrate and sodium chloride forms insoluble silver chloride. Learn more.

AgNO₃ (aq) + NaCl (aq) → AgCl (s) + NaNO₃ (aq)

Crystallization of Salts

Evaporate the water from a salt solution to obtain pure crystals. This method ensures highly pure soluble salts, widely used in laboratories.

Table: Methods and Example Salts

Method	Reactants	Example Salt Formed
Acid + Metal	H₂SO₄ + Zn	ZnSO₄
Acid + Base	HCl + NaOH	NaCl
Double Displacement	AgNO₃ + NaCl	AgCl

Quiz: Preparation of Salts

Q1: Which salt forms when hydrochloric acid reacts with sodium hydroxide?
A) NaCl
B) Na₂SO₄
C) KNO₃
D) CaCl₂

Answer: A) NaCl
Explanation: This is a classic neutralization reaction where acid reacts with a base to form salt and water.

Q2: What gas evolves when an acid reacts with a carbonate?
A) Oxygen
B) Hydrogen
C) Carbon Dioxide
D) Chlorine

Answer: C) Carbon Dioxide
Explanation: Carbonates react with acids to produce salts, water, and CO₂ gas.

Q3: Identify the precipitation reaction.
A) HCl + NaOH → NaCl + H₂O
B) AgNO₃ + NaCl → AgCl + NaNO₃
C) Zn + HCl → ZnCl₂ + H₂
D) CaCO₃ + HCl → CaCl₂ + CO₂ + H₂O

Answer: B) AgNO₃ + NaCl → AgCl + NaNO₃
Explanation: AgCl precipitates as it is insoluble in water.