Equilibrium constant calculations.

Question

A chemistry student dropped 100 g of pure zinc into 2.0L of a 1.00M solution of Cu ions.
Zn(s) + Cu(aq)-----Cu(s)+Zn(aq)
at equilibrium the chemist found that 75.0 g of pure solid copper had been formed. calculate the equilibrium constant.( K )

thankyou.

Answer 1

Equilibrium constant is a ration of concentrations of products over concentration of reagents. Solid parts of the reaction are not taken into consideration, since they are not a part of the solution per se. So, in your case the expression would be:

 

K=[Zn²⁺]/[Cu²⁺]

 

By knowing how much copper was precipitated out of the solution, you can calculate how much is left.

Since the reaction has 1-to-1 stoichiometry, you can now calculate how much zinc you have in the solution.

Finally, put the resulting concentrations into equilibrium constant expression.