Acid Base PH, POH

Question

Determine the pH of a 5.6 ×10^−4 M solution of Ca(OH)2.

Answer 1

In order to answer this question, you have to know the relationships between the concentration of OH- and pH. Ca(OH)₂ dissociates into Ca²⁺ and OH^-. Since it is a strong base (all Group 1 and Group 2 hydroxides are strong bases), it will dissociate completely. You can use the concentration they provide to then find the concentration of OH^- ions in solution (remember it will be 2 OH^- ions for every calcium hydroxide molecule). Once you have found the concentration of OH^- ions, you can use the formula for pOH

pOH= -log[OH^-]

Once you found the pOH, you have to convert into pH. That's the easy part.

pH + pOH=14

Let me know if you have any questions or if you would like to review Acid/Base chemistry