Properties of Acids and Bases

Properties of Acids and Bases

Some Properties of Acids:

  • Their taste is sour like, lemon, orange.
  • Their solubility in water is high.
  • Their water solutions conduct electric current.
  • Compounds including CO3-2and HCO3- produce CO2 gas;


CaCO3 + 2HNO3 → Ca(NO3)2 + CO2(g) + H2O

NaHCO3 + HCl → NaCl + CO2(g) + H2O

  • They react with active metals and produce salt and H2 gas.


Zn + H2SO4(sol) → ZnSO4(sol) + H2(g)

Mg + 2HCl → MgCl2 + H2

2Al + 3H2SO4 → Al2(SO4)3 +3H2

Some of the metals like Au, Pt, Ag, Cu and Hg are  exceptions of this property. They are called noble metals. They do not form H2 gas in reactions with acids. However, some of noble metals react with HNO3 and H2SO4 and do not produce H2.


Cu + HCl → No reaction occurrs

Cu + 2H2SO4 → CuSO4 + SO2 + 2H2O

3Cu + 8HNO3 → 3Cu(NO3)2 + 2NO + 4H2O

  • Acids turn blue litmus to red.
  • Acids react with bases and form salt and water. This reaction type is called neutralization reaction .

H2SO4 + 2NaOH → Na2SO4 + 2H2O

2HCl + Ba(OH)2 → BaCl2 + 2H2O

HCl + NaOH → NaCl +H2O

Some Properties of Bases:

  • Their taste is bitter like shampoo.
  • Their solutions with water conduct electric current.
  • When we touch basic matter, we feel them slippery.
  • Their solubility in water is low with respect to acids.
  • Bases turn red litmus to blue.
  • They do not react with metals. However, some of the metals like Zn and Al react with bases and form H2 gas and salt. These metals are called amphoteric metals. They behave like acid for base and base for acid.


2Al + 6NaOH → 2Na3AlO3+ 3H2

Zn + 2NaOH → Na2ZnO2 + H2

  • They react with acids and form salt and water. (Neutralization reactions)


Compounds of any element with water are called oxides . We examine them under four titles; acidic and basic oxides, neutral oxides, amphoteric oxides and peroxides;

1) Acidic Oxides: They are oxides which combine with bases and form salt. SO2, SO3, CO2, N2O5 are example of acid oxides.

SO3 +   2 NaOH  →  Na2SO4 +  H2O

Acid Oxide Base           Salt           Water

CO2 + 2 NaOH →  Na2CO3 +   H2O

Acid Oxide   Base           Salt           Water

Acid oxides combine with water and form acids.

SO2 + H2O → H2SO3

SO3 + H2O → H2SO4

CO2 + H2O → H2CO3

2) Basic Oxides: They combine with acids and form salt. Metal oxides show this property like; Na2O, CaO.

Na2O       +   2HCl → 2NaCl + H2O

Basic Oxide   Acid      Salt    Water

CaO     +    2HCl → CaCl2 + H2O

Basic Oxide   Acid    Salt    Water

Basic oxides combine with water and form bases.

Na2O + H2O → 2NaOH

BaO + H2O → Ba(OH)2

3) Neutral Oxides: They are do not react with acids and bases. Neutral oxides do not react with water and form acid or base. NO, N2O and CO are some examples of neutral oxides.

4) Amphoteric Oxides: These oxides react with acids and bases and form salt. ZnO and Al2O3 are examples of amphoteric oxides. Examples of these reactions are given below;

ZnO + 2HCl → ZnCl2 + H2O

ZnO + 2NaOH → Na2ZnO2 + H2O

Al2O3 + 6HCl → 2AlCl3 + 3H2O

Al2O3 + 6NaOH → 2Na3AlO3 + 3H2O

5) Peroxides: Compounds including (O2)-2 in their structure are called peroxides. Examples of peroxides are given below;

H2O2: Hydrogen Peroxide

Na2O2: Sodium Peroxide

Example: Which ones of the following statements are true for water solution of sulfuric acid H2SO4?

I. It turns color of litmus to red.

II. It conducts electric current.

III. When it reacts with Mg, H2 gas is formed.

IV. It does neutralization reaction with water solution of NH3.


Since it is acid, it turns blue litmus to red I is true.

All of the acidic water solutions conduct electric current so II is true.

Some of the metals react with acids and H2 gas is formed, Mg is one of that metals III is also true.

NH3 is base and H2SO4 is acid, when they combine neutralization reaction occurs. IV is also true.

Acids and Bases Exams and Problem Solutions