[ghostanime2001]

This is from a worksheet in Grade 12 Chemistry. This is question 11.f) I know how to do all the other compounds except this one:

When the following substances are introduced into water do the resulting equilibria favour products or reactants?
 c)MgO

I know that when I introduce a metal oxide in water, the product will be a metal hydroxide so:

MgO + H₂O  Mg(OH)₂

I don't know what to do next or how to calculate the equilibrium constant for magnesium oxide, I know the K_a of the reactant acid is H₂O but I do not know the Ka of the product acid because it is a base.  So what should I do next ? I have uploaded the worksheet I was given in Grade 12 Chemistry. Thanks so much for anyone's help !!

{MOD Edit: Remove attachments}

[Arkcon]

Please only ask one question.  You reproduced 4 pages of a textbook, that is getting close to a copyright violation.  Those pages had dozens of questions, none of which matched the one you asked  11.F)  And we'd like to see a little work, that includes typing in the problem into this forum when possible.  If you feel the need to repost the scanned question, then zoom in on the image to ask just the question at hand.

[Borek]

He meant A-11, point f.

[Arkcon]

Ah.  OK.  ghostanime2001:, lets try and have the question again.  Sorry.

[ghostanime2001]

I have included the original two pages from last time and another 2 pages incase other information need be required to solve.

[Borek]

As far as I can tell there is no way to answer the question using methods and information from this chapter.

[ghostanime2001]

Should I upload page 3 ? lol I did not feel the need to upload page 3 because the information on that page deviates from the method on page 4 and page 5. Also, if anyone knows from what textbook this information comes from, that would really help I could search for the book. My Chemistry teacher told me this is from the 1970's or 80's :S

[Xilaim]

Determine the equilibrium constant is not necessary:
MgO concentration (solid) = 1
The concentration of H₂O (water surplus) = 1
The concentration of Mg(OH)₂ (solid) = 1

answer: equilibria favour products.

[Borek]

Determine the equilibrium constant is not necessary:
MgO concentration (solid) = 1
The concentration of H₂O (water surplus) = 1
The concentration of Mg(OH)₂ (solid) = 1

answer: equilibria favour products.

Following this logic Al₂O₃ should react with water producing Al(OH)₃. It doesn't.

[Xilaim]

  Ok Ok
Here's the formula for the solution to the Gibbs energy: lgK = ΔG₂₉₈/(-2.3*R*T)
R = const = 0.0083
T = 298K

[Borek]

Ok Ok
Here's the formula for the solution to the Gibbs energy: lgK = ΔG₂₉₈/(-2.3*R*T)
R = const = 0.0083
T = 298K

Yes. And area of the circle is [itex]\pi r^2[/itex]. Neither equation helps answer the question.

[Xilaim]

Wrong equation?

[Borek]

Show how you are going to use it to solve the problem. Note that you are not given ΔG, and the chapter is on acid/base equilibrium, so all data you have at hand are K_a values.

[ghostanime2001]

would knowing the base dissociation constant for O^-2 help ? by the way, what is the K_b value for the oxygen anion ?

[Xilaim]

Show how you are going to use it to solve the problem. Note that you are not given ΔG, and the chapter is on acid/base equilibrium, so all data you have at hand are K_a values.

ΔG - reference have chemistry.

MgO + H₂O  Mg(OH)₂

Excess water will shift the equilibrium in the reaction products.
The solubility product = [Mg²⁺] [OH^-]² = 6.0 x 10 ^ -10
K = [OH-]/Kw
Kw = 1e-14