# 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?

NH_3(aq) + H_2O(l) rightleftharpoonsNH_4^(+) + ""^(-)OH
K_b=([H_4N^(+)][""^(-)OH])/([NH_3(aq)]) $=$ ${10}^{- 4.75}$
The concentration of $\left[H {O}^{-}\right]$ in such solutions is low.
As for the use of ammonia in window cleaner, I suspect the percentage of ammonia in such a product is approx. 5-10%(w/w). With normal use (with gloves), the solution is probably formulated so that it is not too hard on your hands. Ammonia solutions are known to give so-called $\text{streak free}$ finishes on glass and metal surfaces.