Question

When the first element of the periodic table is treated with dioxygen, it gives a compound whose solid state floats on its liquid state. This compound has an ability to act as an acid as well as a base. What products will be formed when its compound undergoes autoionisation ?

Answer 1

Hi,

Here is your answer,

The first element of the periodic table is hydrogen and its molecular form is dihydrogen (H₂). When H₂ reacts with Oxygen (O₂) water is formed. Water is a liquid at room temperature. When liquid freezes, it expands to form ice.

Density of ice is lower than that of liquid water and hence ice floats over water. Water is amphoteric in nature. It acts as a base in presence of strong acids and as an acid in presence of strong bases.

                          H₂O (l) + H₂S (aq) ----> H₃O⁺(aq) + HS⁻(aq) 
                           Base₁       Acid₂               Acid₁          Base₂

                         H₂O (l) + NH₃ -----> NH₄⁺ (aq) + OH⁻ (aq)
                          Acid₁        Base₂         Acid₂             Base₁

Now, Due to amphoteric character, water undergoes self ionisation.

                      H₂O (l) + H₂O (aq) ------> H₃O⁺ (aq) + OH⁻ (aq)
                       Acid₁       Base ₂                Acid₂          Base₁{Conjugate Base}
                                                            { Conjugate Acid }

 
The self ionisation of water is called auto-protolysis or autoionisation.



Hope it helps you !