Explanation:

A. 2.00 mL of 0.00250 M 
Moles of ferric nitrate = n
Volume of ferric nitrate = 2.00 ml = 0.002 L ( 1 mL=0.001 L)
Molarity of ferric nitrate = 0.00250 M

B. 5.00 mL of 0.00250 M 
Moles of KSCN = n'
Volume of KSCN = 5.00 ml = 0.005 L ( 1 mL=0.001 L)
Molarity of KSCN = 0.00250 M

C. 3.00 mL of 0.050 M 
Moles of nitric acid = n''
Volume of nitric acid = 3.00 ml = 0.003 L ( 1 mL=0.001 L)
Molarity of nitric acid = 0.050 M

After mixing A, B and C together and their respective initial concentration before reaction.
After mixing A, B and C together the volume of the solution becomes = V
V = 0.002 L=0.005 L+0.003 L= 0.010 L
Concentration of ferric nitrate :
![[Fe(NO_3)_3]=\frac{0.000005 mol}{0.010 L}=0.0005 M](https://tex.z-dn.net/?f=%5BFe%28NO_3%29_3%5D%3D%5Cfrac%7B0.000005%20mol%7D%7B0.010%20L%7D%3D0.0005%20M)
Concentration of ferric ions :
![[Fe^{3+}]=1\times [Fe(NO_3)_3]=0.0005 M](https://tex.z-dn.net/?f=%5BFe%5E%7B3%2B%7D%5D%3D1%5Ctimes%20%5BFe%28NO_3%29_3%5D%3D0.0005%20M)
Concentration of nitrate ions from ferric nitrate:
![[NO_3^{-}]=3\times [Fe(NO_3)_3]=0.0015 M](https://tex.z-dn.net/?f=%5BNO_3%5E%7B-%7D%5D%3D3%5Ctimes%20%5BFe%28NO_3%29_3%5D%3D0.0015%20M)
Concentration of KSCN :
![[KSCN]=\frac{0.0000125 mol}{0.010 L}=0.00125 M](https://tex.z-dn.net/?f=%5BKSCN%5D%3D%5Cfrac%7B0.0000125%20mol%7D%7B0.010%20L%7D%3D0.00125%20M)
Concentration of
ions:
![[SCN^-]=1\times [KSCN]=0.00125 M](https://tex.z-dn.net/?f=%5BSCN%5E-%5D%3D1%5Ctimes%20%5BKSCN%5D%3D0.00125%20M)
Concentration of potassium ions:
![[K^+]=1\times [KSCN]=0.00125 M](https://tex.z-dn.net/?f=%5BK%5E%2B%5D%3D1%5Ctimes%20%5BKSCN%5D%3D0.00125%20M)
Concentration of nitric acid :
![[HNO_3]=\frac{0.00015 mol}{0.010 L}=0.015 M](https://tex.z-dn.net/?f=%5BHNO_3%5D%3D%5Cfrac%7B0.00015%20mol%7D%7B0.010%20L%7D%3D0.015%20M)
Concentration of hydrogen ion :
![[H^+]=1\times [HNO_3]=0.015 M](https://tex.z-dn.net/?f=%5BH%5E%2B%5D%3D1%5Ctimes%20%5BHNO_3%5D%3D0.015%20M)
Concentration of nitrate ions from nitric acid :
![[NO_3^{-}]=1\times [HNO_3]=0.0015 M](https://tex.z-dn.net/?f=%5BNO_3%5E%7B-%7D%5D%3D1%5Ctimes%20%5BHNO_3%5D%3D0.0015%20M)
Concentration of nitrate ion in mixture = 0.0015 M + 0.0015 M = 0.0030 M

given concentration of
at equilbrium = 
initially :
0.0005 M 0.00125 M 0
At equilibrium
(0.0005-0.000036) M (0.00125-0.000036) M 0.000036 M
0.000464 M 0.001214 M 0.000036 M
The expression of an equilibrium constant will be given as;
![K_c=\frac{[Fe(NCS)^{2+}]}{[Fe^{3+}][SCN^{-}]}](https://tex.z-dn.net/?f=K_c%3D%5Cfrac%7B%5BFe%28NCS%29%5E%7B2%2B%7D%5D%7D%7B%5BFe%5E%7B3%2B%7D%5D%5BSCN%5E%7B-%7D%5D%7D)

The value for the equilibrium constant is 63.91.