Question

How do you write the chemical equation and ${K_b}$ expression for the ionization of ammonia in water? How is it safe for a window cleaner to use a solution of ammonia, which is basic?

Answer 1

The base dissociation constant is represented as ${K_b}$ . In the presence of water, it measures how the base dissociates into its components. If the value of ${K_b}$ is high, then it’s a strong base as the dissociation constant is also high or else it will be a weak base.

Complete answer:
The chemical equation of ammonia with water is:
$N{H_3} + {H_2}0 \rightleftharpoons NH_4^ + + {}^ - OH$ $$
The value of ${K_b}$ is calculated as:
{K_b} = \dfrac{{\left[ {{H_4}{N^ + }} \right]\left[ {{}^ - OH} \right]}}{{\left[ {N{H_3}} \right]}} \\\ {K_b} = {10^{ - 4.75}} \\\
Hence, the value of ${K_b}$ is ${10^{ - 4.75}}$ .
Ammonia is widely used as a liquid for cleaning products. In window cleaners the percentage of Ammonia is approximately five to ten percent. It is a colourless gas and it evaporates quickly. Due to this rapid evaporation, there are no streaks left behind. It doesn’t allow dirt and dust to stick on to the glass.

Note:
If we use ammonia based glass cleaners to clean the glass in direct sunlight, then we will notice streaks on the glass. This is because the liquid dries up before the evaporation process is instantiated. It is also not preferable to use ammonia cleaners to clean tinted glass as it discolours the glass and makes it hazy.