III. Mass Percent of Ni2+in Ni(NH 3 ) nCl 2

a. molar mass of NiSO 4 ⋅6 H 2 O = 262.88 g ⋅ mol–1

b. mass of NiSO 4 ⋅6 H 2 O = 0.3000 g

c. mass of Ni(NH 3 )nCl 2 = 0.3500 g

d. initial color of NiSO 4 solution = blue-green

e. initial color of Ni(NH 3 ) nCl 2 solution = bluish-purple

f. final color of NiSO 4 after NH 3 added = bluish-purple

g. final color of Ni(NH 3 ) nCl 2 after NH 3 added = bluish-purple

IV. %T for the standard [Ni(NH 3 )n]2+

Wavelength (nm) %T of the standard

[Ni(NH 3 )n]2+sol’n

540 36.4

560 15.5

580 7.5

600 5.2

620 8.1

640 16.3

Approximate λmaxof [Ni(NH 3 )n]2+ion (nm) = 600 nm

%T of the standard [Ni(NH 3 )n]2+solution at 600 nm = 5.2

%T of the unknown [Ni(NH 3 )n]2+= 22.4

V. Analysis

Mass Percent of NH 3 in Ni(NH 3 )nCl 2

Recap: Excess HCl was added to the synthesized Ni(NH 3 )nCl 2 to form NH 4 +. The

solution was then titrated with NaOH to reach an endpoint of 5.1.

1. Determine the number of moles of HCl originally.
   ..
   '.

mL HCl

mL

L

L sol n

mol HCl moles HCl

1

25 0

1000

1

1

##0 250 =0 00625

2. Determine the number of moles of NaOH added.
   ..
   '.

mL NaOH

mL

L

L sol n

mol NaOH moles NaOH

1

29 6

1000

1

1

##0 100 =0 00296

3. Determine the number of moles of HCl that remained after the NH 3 was neutralized.
   ..
   '

mL NaOH

mL

L

L sol n

mol NaOH

mol NaOH

mol HCl

1

29 6

1000

1

1

0 100

1

###^1 = 0.00296 mol HCl

4. Determine the number of moles of NH 3 in the Ni(NH 3 )nCl 2 sample.
   = 0.00625 mol HCl – 0.00296 mol NaOH = 0.00329 mol HCl used to react with
   the NH 3
   .
   .

mol HCl

mol HCl

mol NH mol NH

1

0 00329

1

(^13) 0 00329

= (^3299)

Laboratory Experiments