Call

The trick here is to make sure that you do not include the concentrations of the two solids, nickel(II) oxide and nickel metal, in the expression of the equilibrium constant, $K_c$.

In this regard, the expression of the equilibrium constant will depend exclusively on the concentrations of carbon monoxide, $"CO"$, and of carbon dioxide, $"CO"_2$.

$K_c = (["CO"_2])/(["CO"])$

Now, you know that you're starting with $"0.10 M"$ of carbon monoxide and an unknown quantity of nickel(II) oxide. Notice that the reaction produces $1$ mole of carbon dioxide for every mole of carbon monoxide that takes part in the reaction.

If you take $x$ to be the concentration of carbon dioxide formed by the reaction, i.e. the concentration of carbon dioxide at equilibrium, you can say that

$["CO"_2] = x$

$["CO"] = 0.10 - x$

Plug this into the expression of $K_c$ and solve for $x$

$4.0 * 10^3 = x/(0.10 - x)$

This gets you

$x = 4 * 10^3 * (0.10 - x)$

$x = 4 * 10^2 - 4 * 10^3x$

$x * (4 * 10^3 + 1) = 4 * 10^2$

$x = (4 * 10^2)/(4 * 10^3 + 1) = 0.099975$

Notice that the answer must be rounded to two , since that is how many sig figs you have for the concentration of carbon monoxide, so

$["CO"_2] = color(green)(bar(ul(|color(white)(a/a)color(black)("0.10 M")color(white)(a/a)|)))$

Keep in mind that you have

$["CO"] = "0.10 M" - "0.10 M" ~~ "0.00 M"$

because

$["CO"] = "0.10 M" - "0.099975 M" = "0.000025 M"$

and

$"0.000025 M" = "0.00 M" " ->$ rounded to two decimal places

Talk Doctor Online in Bissoy App