If the concentration of barium hydride solution is 0.398 molar, calculate its pOH. Barium hydride represents a strong base. Remember, strong bases completely ionize into ions. So, here we form one barium ion plus two hydride ions. The concentration of the strong base is 0.398 molar. Because we produce two hydride ions it'd be 2 times 0.398 molar to get its real concentration. When we do that we get 0.796 molar as the concentration of our hydride ion.

Now, remember that the concentration of hydride ion is equal to the concentration of hydroxide ion. This is important because now that we know the concentration of hydroxide ion, we can find the pOH. pOH itself equals negative log of OH− concentration. So, plug in 0.796, and when we do that, we're gonna get 0.0991 as the pOH of our barium hydride solution.