2. How many moles of FeSCN2+were in the mixture at equilibrium?

Total volume of sol’n = 5.0 mL + 5.0 mL = 10.0 mL

+

'

. .'.
L sol n

13 10 moles FeSCN L sol n moles FeSCN

1

0 0100

13 10

#^4262

##=

-+ -

3. How many moles of Fe3+and SCN–were used up in making the FeSCN2+?

The balanced equation at equilibrium is:

Fe++SCN FeSCN

aq aq aq

(^32) + - E
]]]ggg
The ratio of Fe3+to SCN–is 1:1 and the ratio of Fe3+and SCN–to FeSCN2+is 1:1
Therefore, 1.3 × 10 –6moles of Fe3+and 1.3 × 10 –6moles of SCN–were used in making the
FeSCN2+.

4. How many moles of Fe3+and SCN–remain in the solution at equilibrium?

initial # of moles −# of moles used up in making FeSCN2+

= 1.0 × 10 –5moles Fe3+−1.3 × 10 –6moles Fe3+= 8.7 × 10 –6moles Fe3+

= 1.0 × 10 –5moles SCN–−1.3 × 10 –6moles SCN–= 8.7 × 10 –6moles SCN–

5. What are the concentrations of Fe3+, SCN–, and FeSCN2+at equilibrium?

4 +

.'

Fe..

L sol n

moles Fe MFe

001

3 + ==87 10# -+^63 87 10# - 3

7A

6

.'

SCN..

L sol n

moles SCN M SCN

001

• ==87 10# --87 10# - 4 -
  7A

[FeSCN2+] = 1.3 x 10–4M FeSCN2+

6. Determine Kcfor the reaction.

Fe++SCN FeSCN

()aq ()aq ()aq

(^32) + - E
.
K..
Fe SCN
FeSCN
M
M M
87 10
13 10 17 10
c 3
2
4 2 2
(^421)

== =# #
+-

(^77) _i
7
AA
A
Laboratory Experiments