When you add ammonia to a solution it is important to remember that you change the concentration of the hydroxide ions present because of the reaction: nh4 (aq) + oh (aq) nh3(ac) + h2o0 remembering this will you with at least two of the steps in this exercise. in many metal-containing solutions, the addition of ammonia causes a hydroxide precipitate to form. select the statement below which best describes this observation. select one: a. the addition of nh3 causes the ph to increase thus increasing the [oh]. x b. the addition of nh3 causes the ph to decrease thus increasing the [oh]. c. the addition of nh3 results in a reaction between ammonia and oh, causing the ph to increase. d. the addition of nh3 results in a reaction between ammonia and water, causing [oh] to increase.