Question

What is meant by the concentrated alkali and dilute alkali?

What are the general methods of preparation of bases?

Answer 1

Part1- Concentrated solution

A Concentrated solution contains a relatively large amount of solute and a dilute solution contains a relatively small amount of dissolved solute.

Part 2- Definition of concentrated alkali and dilute alkali

Concentrated alkali - in a concentrated alkali solution, the alkali solutes are relatively large in amount than the water.

Dilute alkali-

1. In a dilute alkali solution, the alkali solute is relatively lesser than the amount of water.
2. It is prepared by taking a small portion of concentrated alkali with a large amount of water.

Part 3- The general method of preparation of bases

(A) The direct union of a metal with oxygen form an oxide, which further dissolves with water and form hydroxide bases. $$\begin{gathered} \left(1\right)4\mathrm{Na}\left(\mathrm{s}\right)+{\mathrm{O}}_2\left(\mathrm{g}\right)\to 2{\mathrm{Na}}_2\mathrm{O}\left(\mathrm{s}\right) \\ (\mathrm{Sodium}\mathrm{metal})\left(\mathrm{Oxygen}\right)(\mathrm{Sodium}\mathrm{oxide}) \\ \mathrm{Hydrolysis} \\ {\mathrm{Na}}_2\mathrm{O}\left(\mathrm{s}\right)+{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)\to 2\mathrm{NaOH}\left(\mathrm{aq}\right)\left(\mathrm{Base}\right) \\ \left(\mathrm{oxide}\right)(\mathrm{Sodium}\mathrm{hydroxide}) \\ \left(2\right)4\mathrm{K}\left(\mathrm{s}\right)+{\mathrm{O}}_2\left(\mathrm{g}\right)\to 2{\mathrm{K}}_2\mathrm{O}\left(\mathrm{s}\right)\left(\mathrm{oxide}\right) \\ (\mathrm{Potassium}\mathrm{metal})\left(\mathrm{Oxygen}\right)(\mathrm{Potassium}\mathrm{oxide}) \\ \mathrm{Hydrolysis} \\ {\mathrm{K}}_2\mathrm{O}\left(\mathrm{s}\right)+{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)\to 2\mathrm{KOH}\left(\mathrm{aq}\right)\left(\mathrm{Base}\right) \\ (\mathrm{Potassium}\mathrm{oxide})(\mathrm{Potassium}\mathrm{hydroxide}) \end{gathered}$$

(B) By direct hydrolysis of active metal with cold water

$$\begin{gathered} 2\mathrm{Na}\left(\mathrm{s}\right)+2{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)\to 2\mathrm{NaOH}\left(\mathrm{aq}\right)+{\mathrm{H}}_2\left(\mathrm{g}\right) \\ (\mathrm{Active}\mathrm{metal})\left(\mathrm{cold}\right)\left(\mathrm{Base}\right)\left(\mathrm{Hydrogen}\right) \\ 2\mathrm{K}\left(\mathrm{s}\right)+2{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)\to 2\mathrm{KOH}\left(\mathrm{aq}\right)+{\mathrm{H}}_2\left(\mathrm{g}\right) \\ (\mathrm{Active}\mathrm{metal})\left(\mathrm{cold}\right)\left(\mathrm{Base}\right)\left(\mathrm{Hydrogen}\right) \end{gathered}$$