In: Chemistry
Assuming complete dissociation, what is the pH of a 4.21 mg/L Ba(OH)2 solution?
pH=
Molar mass of Ba(OH)2 = 171.34 g/mol
Lets assume 1 L of solution.
Mass = 4.21 mg = 4.21*10^-3 g
Number of moles =mass/ molar mass
= (4.21*10^-3)/ 171.34
= 2.457*10^-5 mol
[Ba(OH)2] = number of moles / volume
= 2.457*10^-5 / 1
= 2.457*10^-5 M
Ba(OH)2 ----> Ba2+ + 2 OH-
So,
[OH-]= 2*[Ba(OH)2] = 2*2.457*10^-5= 4.91*10^-5 M
pOH = - log [OH=]
= -log (4.91*10^-5)
= 4.31
pH= 14- pOH
= 14- 4.31
=9.69
Answer: 9.69