What do we use ammonia for in chemistry?

Chemistry Homework Question: How do you calculate the pH of a mixture of two solutions?  In this case, distilled water and an ammonia solution.

• I do not know any chemistry at all, but I am quite fluent in mathematics.  Could you explain how to do this calculation when I don't know what the concentration of the ammonia solution I am using?

• Answer:

  pH of a solution can be calculated by measuring the [math]H+[/math] or the [math]OH-[/math] ion concentration and using the formula: [math]pH=log(H+)[/math] or [math]pH=14+log(OH-)[/math] Both logs in base 10. Ammonia deprotonates the water molecule in an aqueous solution. The reaction for it is: [math]NH3+H2O=NH4+OH[/math] The base ionization constant for ammonia, Kb is 1.8e-5 So, [math]1.8e-5=(NH4+)(OH-)/(NH3)[/math] and [math](NH4+)=(OH-)[/math] [math](OH-)^2=1.8e-5*(NH3)[/math] If you know the initial concentration of the ammonia solution you mixed with the distilled water, you can calculate the OH- ion concentration in the final solution. Using that, you can calculate the pH of the final solution.