calculation of hydroxide ion concentration

[Guest locket]

I am really struggling with an assignment. To most it may seem simple (so HELP!!!!) but as a maths major I cannot for the life of me remember my high school chemistry.

Q: At 25degC. 0.212g of barium hydroxide is dissolved completely in sufficient water to make 0.25 litre of final solution. What is the hydroxide ion concentration and the hyrogen ion concentration (in mol-1 litre) in this solution?

Please can someone help. I really do not want to flunk any of my assignments and am really struggling with this one.

[wolfson]

Molar mass of Ba(OH)2 --- 137.3 + (17 x 2) =171.3

 

Number of moles of Ba(OH)2 in 0.212g =0.0012 moles

 

Molarity = Number of mole (n) / volume of solution

 

M = 0.0012 / 0.25 = 0.0048 Molarity

 

[OH-] = 1.0e-14 (e=x10) / 0.0048 = 2.08e-12 mol dm^3

 

(1e-14 is the water constant Kw).

 

In basic solns, the [H+] < [OH-] \ [H+] < 1 X 10-7 M

[Guest locket]

Thank a lot. I actually did the first part correctly but really screwed up the last part. I actually used to love chemistry but now cannot remember a thing.

[wolfson]

your welcome anytime you need help math or chem just ask