Potassium thiocyanate, kscn, is often used to detect the presence of fe3+ ions in solution through the formation of the red fe(h2o)5scn2+ (or, more simply, fescn2+). what is [fe3+] when 0.700 l each of 0.00150 m fe(no3)3 and 0.200 m kscn are mixed? kf of fescn2+ = 8.9 × 102. enter your answer in scientific notation. report your final answer to two significant figures.

Ferric ions left in the solution at equilibrium is .

Explanation:

Moles of ferric nitrate in 0.700 L = n

Volume of the solution = V = 0.700 L

Molarity of ferric nitrate = M = 0.00150 M

Moles of potassium thiocyanate in 0.700 L = n'

Volume of the potassium thiocyanate solution = V' = 0.700 L

Molarity of potassium thiocyanate = M' = 0.200 M

Molarity of ferric ions after mixing :

1 mol of ferric nitrate gives 1 mol of ferric ions.Then 0.00105 mol ferric nitrate will :

Moles of ferric ions = 0.00105 mol

Molarity of  thiocyanate ions after mixing :

1 mol of potassium thiocyanate gives 1 mol of thiocyanate ions.Then 0.140 mol potassium thiocyanate will give:

Moles of thiocyanate ions = 0.140 mol

Complex equation:

0.00075 M         0.1 M                        0

At equilibrium:

(0.00075 M -x)    (0.1 M-x)                  x

The formation constant of the given complex =

Solving for x:

x = 0.000742 M

Ferric ions left in the solution at equilibrium :

= (0.00075 M -x) = (0.00075 M - 0.000742 M)=

there are two significant figures.