Answer the following questions regarding the synthesis and analysis of a Nickel

Question

Answer the following questions regarding the synthesis and analysis of a Nickel coordination compound (10 points) 2- a. Why is it necessary to wash the filtered Ni(NH3)nC12 crystals with concentrated NH3? b. What method is used to determine the amount of NH3 in the coordination compound? c. What method is used to determine the amount of Ni2+ in the coordination compound? d. Calculate the absorbance of a sample with a %T of 3.98. e. What is the concentration of Ni2+ in an unknown sample whose absorbance is 0.45 if a standard solution of 2M Ni2+ had an absorbance of 0.3?

Explanation / Answer

2- Peparation of nickel coordinate complex

a. The crystals Ni(NH3)nCl2 are washed with concentrated NH3 to ensume no unreacted Ni(OH)2 is left in the solution and all of them is converted into the coordinate complex.

b. To determine the amount of NH3 in the complex, the complex is treated with HCl, all of NH3 from complex forms NH4Cl. So the moles of HCl reacted would be equal to the moles of NH3 present in the complex and in turn amount of NH3 in the sample.

c. To determine amount of Ni2+ in the complex, the complex is redissolved and reprecipitated with say dimethylglyoximate (DMG). the mole of Ni2+ reacts with 2 moles of DMG. So the amount of DMG consumed would give us the amount of Ni2+ in the complex.

d. absorbance = 2 - log(%T)

with, %T = 3.98

Absorbance = 2 - log(3.98) = 1.4

e. Standard solution concentration = 2 M, with absorbance = 0.3

Let x be the concentration of Ni2+ in unknown solution, then,

x/2 = 0.45/0.3

concentration of Ni2+ in the sample = x = 0.45 x 2/0.3 = 3 M

Related Questions

Navigate

• Browse (All)
• Browse A
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.