Originally Posted by
TheMasterMind This is a very simple problem, knowing the value of 14 on the pH scale is the value you need.
$\displaystyle pH + pOH = 14$
$\displaystyle pOH = 14 - pH$
$\displaystyle = 14 - 6.4$
$\displaystyle = 7.6$
$\displaystyle \therefore $The pOH is 7.6