Astandard solution of fescn2+ is prepared by combining 9.0 ml of 0.20 m fe(no3)3 with 1.0 ml of 0.0020 m kscn . the standard solution had an absorbance of 0.480 . fe3+(aq)+scn−(aq)↽−−⇀fescn2+(aq) a trial solution was made in a similar manner, but with a more dilute fe(no3)3 reagent. the initial scn− concentration, immediately after mixing, was 0.00050 m . this trial solution had absorbance of 0.220 . what is the equilibrium concentration of scn− in the trial solution?

Answer : The equilibrium concentration of in the trial solution is

Explanation :

First we have to calculate the initial moles of and .

and,

The given balanced chemical reaction is,

Since 1 mole of reacts with 1 mole of to give 1 mole of

The limiting reagent is,

So, the number of moles of = 0.0020 mmole

Now we have to calculate the concentration of .

Using Beer-Lambert's law :

where,

A = absorbance of solution

C = concentration of solution

l = path length

= molar absorptivity coefficient

and l are same for stock solution and dilute solution. So,

For trial solution:

The equilibrium concentration of is,

= 0.00050 M

Now calculate the .

Now calculate the concentration of .

Therefore, the equilibrium concentration of in the trial solution is