Please help me, I really need it, God Bless you <3

What is the [oh-] in a solution with a poh of 3.90

Kc = 0.040 for the system below at 450oc. if a reaction is initiated with 0.40 mole of cl2 and 0.40 mole of pcl3 in a 2.0 liter container, what is the equilibrium concentration of cl2 in the same system? pcl5(g) ⇄ pcl3(g) + cl2(g)

When you mate two plants together the terms is called? answer it fast as possible plz! i have a test tomorrow!