# Question #c3b18

##### 1 Answer

#### Explanation:

All you have to do here is to write the expression for the equilibrium constant that describes this equilibrium.

The equilibrium constant tells you the **ratio** that exists between the **product** of the concentrations of the *products* raised to the power of their respective stoichiometric coefficients and **product** of the concentrations of the *reactants* raised to the power of their respective stoichiometric coefficients.

So

#K_c = "product of concentrations for products"/"product of concentrations for reactants"#

In your case, you have a single product and

#K_c = (["CH"_2"O"])/(["H"_2] * ["CO"])#

Now, you know that

#K_c = 1#

This tells you that, at equilibrium, you have

#["CH"_2"O"] = ["CO"] * ["H"_2]#

Plug in your values to find

#["CH"_2"O"] = "0.200 M" * "0.100 M"#

#["CH"_2"O"] = color(darkgreen)(ul(color(black)("0.0200 M")))#