|
Reaction of Acids and Bases with Metals
|
- When metal reacts with the acids it forms a compound called a salt and hydrogen gas.
Acid + Metal → Salt + Hydrogen gas
2NaOH (aq) + Zn (s) → Na2ZnO2(s) + H2(g)
(Sodium zincate)
- Reactions of metal with the bases are not possible.
|
|
Acids and Base: Metal Carbonates and Hydrogen Carbonates Reactions
|
- All metal carbonates and hydrogen carbonates react with acids to give a corresponding salt, carbon dioxide and water. This interaction underscores the chemical interplay between acids and bases in producing specific compounds.
- Metal carbonate/Metal hydrogen carbonate + Acid → Salt + Carbon dioxide + Water
- Example:
- Na2CO3(s) + 2HCl(aq) → 2NaCl(aq) + H2O (l) + CO2(g)
- NaHCO3(s) + HCl(aq) → NaCl(aq) + H2O (l) + CO2(g)
- On passing the carbon dioxide gas evolved through lime water,
Ca(OH)2(aq) + CO2(g) → CaCO2(s) + H2O(l)
(Lime water) (White precipitate)
- On passing excess carbon dioxide
CaCO3(s) + H2O(l) + CO2(g) → Ca(HCO3)2 (aq)
- Limestone, chalk and marble are different forms of calcium carbonate.
|
|
Acids and Base: Metallic Oxides and Acid Reactions
|
- The general reaction between a metal oxide and an acid can be written as;
Metal oxide + Acid → Salt + Water
CuO(s) + 2HCl(l) → CuCl2(l) + H2O(l)
- Since metallic oxides react with acids to give salts and water, similar to the reaction of a base with an acid, metallic oxides are said to be basic oxides. This draws a parallel between the reactions of acids and bases, highlighting the basic nature of metallic oxides.
|
|
Acids and Base: Reaction of a Non-metallic Oxide with Base
|
- The general reaction between a non-metallic oxide and a base can be written as
Nonmetallic oxide + base → Salt + Water
- Example: Calcium hydroxide, which is a base, reacts with carbon dioxide to produce salt and water. This chemical interaction exemplifies the dynamic nature of acids and bases in producing various compounds.
Ca(OH)2(aq) + CO2(g) → CaCO3(s) + H2O(l)
- Since this is similar to the reaction between a base and an acid, it can be concluded that non-metallic oxides are acidic in nature.
|
|
Acids and Bases in a Water Solution
|
- The separation of H+ ion from HCl molecules cannot occur in the absence of water.
HCl + H2O → H3O+ + Cl–
- Hydrogen ions cannot exist alone, but they exist after combining with water molecules.
- Thus hydrogen ions must always be shown as H+(aq) or hydronium ion (H3O+).
H+ + H3O → H3O+
- Bases dissolved in water generate hydroxide (OH–) ions. For example,
NaOH (s) → Na+ (aq) + OH – (aq)
KOH(s) → K+ (aq) + OH – (aq)
Mg(OH)2(s) → Mg2 + (aq) + 2OH – (aq)
- The process of dissolving an acid or a base in water is a highly exothermic one.
- Mixing an acid or base with water results in a decrease in the concentration of ions (H3O+/OH–) per unit volume.
- Such a process is called dilution and the acid or the base is said to be diluted.
|