Question #659e1
1 Answer
Explanation:
Magnesium carbonate is considered insoluble in water, which implies that when you dissolve this salt in water, a dynamic equilibrium exists between the undissolved solid and the dissolved ions.
#"MgCO"_ (3(s)) rightleftharpoons "Mg"_ ((aq))^(2+) + "CO"_ (3(aq))^(2-)" "color(darkorange)((!))#
Some of the solid will dissolve to produce ions, but most of the salt will remain undissolved, i.e. this equilibrium lies to the left.
By definition, the solubility product constant,
#K_(sp) = ["Mg"^(2+)] * ["CO"_3^(2-)]#
The expression for
In your solution, you know that
#["CO"_3^(2-)] = "0.25 M"#
You also know that
#K_(sp) = 6.82 * 10^(-6)#
Your goal here is to determine the concentration of magnesium cations that will satisfy equation
Rearrange the equation to solve for
#["Mg"^(2+)] = K_(ps)/(["CO"_3^(2-)])#
Plug in your values to find
#["Mg"^(2+)] = (6.82 * 10^(-6))/(0.25) = color(darkgreen)(ul(color(black)(2.7 * 10^(-5)color(white)(.)"M")))#