Question #9ad66

1 Answer
Jan 1, 2018

K_c = 5.0 * 10^(-4)Kc=5.0104

Explanation:

For the sake of simplicity, I will use the following notation

  • "CCl"_3"CH"("OH")_2 -> "reactant"CCl3CH(OH)2reactant
  • "CCl"_3"CHO" -> "product"CCl3CHOproduct

The balanced chemical equation that describes this equilibrium will be--keep in mind that you have a 1:11:1 mole ratio between chloral hydrate and chloral!

"reactant"_ ((sol)) rightleftharpoons "product"_ ((sol)) + "H"_ 2"O"_ ((sol))reactant(sol)product(sol)+H2O(sol)

I used ("sol")(sol) to denote the fact that the compounds are dissolved in a solution that does not have water as the solvent.

Now, you know that for every 11 mole of chloral hydrate that dissociates, you get 11 mole of chloral and 11 mole of water.

The initial concentration of chloral hydrate is

["reactant"]_ 0 = "0.010 moles"/"1 L" = "0.010 M"[reactant]0=0.010 moles1 L=0.010 M

The problem tells you that the equilibrium concentration of water is equal to "0.0020 M"0.0020 M. This means that in order for the reaction to produce "0.0020 M"0.0020 M of water, it must also produce "0.0020 M"0.0020 M of chloral and consume "0.0020 M"0.0020 M of chloral hydrate.

So the equilibrium concentration of chloral will be

["product"] = ["H"_ 2"O"] = "0.0020 M"[product]=[H2O]=0.0020 M

and the equilibrium concentration of chloral hydrate will be

["reactant"] = ["reactant"]_ 0 - "0.0020 M"[reactant]=[reactant]00.0020 M

["reactant"] = "0.00080 M"[reactant]=0.00080 M

By definition, the equilibrium constant will be equal to

K_c = (["product"] * ["H"_2"O"])/(["reactant"])Kc=[product][H2O][reactant]

Keep in mind that water is a solute here, so its concentration must be included in the expression of the equilibrium constant.

Plug in your values to find--I'll leave the answer without added units.

color(darkgreen)(ul(color(black)(K_c))) = (0.0020 * 0.0020)/(0.0080) = color(darkgreen)(ul(color(black)(5.0 * 10^(-4))))

The answer is rounded to two sig figs.