what is equilibrium constant in this reaction?

Question

3.1 MOLES OF FeCL3 AND 3.2 MOLES OF NH2SCN ARE ADDED TO ONE LITRE OF WATER. AT EQUILIBRIUM 3 MOLES OF FESCN+2 ARE FORMED. THE EQUILIBRIUM CONSTANT FOR THIS RECTION fe+3 + scn- gives fescn+2?

Answer 1

Hi Bhavna,

The first thing we need to do is realize that there is 1 mole of Fe³⁺ for every 1 mole of FeCl₃, and the same for NH₂SCN and SCN^-. Next, since everything is in the same container, we can use moles as an equivalent to molarity.

So, let's make an ICE diagram (initial, change, and equilibrium concentrations).

 

     Fe³⁺   +   SCN^-  -->  FeSCN²⁺

I    3.1           3.2               0

C    -3             -3              +3

E    0.1          0.2               3

 

Note I figured out the C line AFTER I plugged in 3 for the E line for the product. This then let me figure out the E line for the products.

 

Now we need to use the equation K=[products]/[reactants] to solve for the equilibrium constant, K.

K=3/(0.1*0.2)K=150