Synthesis and Analysis of a Nickel Complex

Give an experimental section for this laboratory experiment.   BOTH WEEKS

Week 1:

Synthesis of a Nickel complex was determined by adding ethylenediamine and ethanol. After obtaining close to 1.000g of nickel(II) sulfate hexahydrate, with your partner as instructed in step one, we quantitatively transferred it to a 250mL beaker with no more than 3mL of water. After the substance had dissolved we added the assigned amount of en to the substance slowly so it could attach to the nickel around the water, as instructed in step 2. Following step 3 in the lab manual we began to add ethanol slowly while stirring to precipitate out the nickel complex. Once the substance settled to the bottom we weighed a new container with the label, filter paper, and beaker, all included in step 4 of the lab manual. Following directions from steps five and six, we used the Buchner funnel to separate the precipitate from the liquid. Once the liquid was washed thoroughly with ethanol we let it dry and moved it to the previously weighed beaker. After this we set it in our lab drawer for it to dry over next week.

Week 2:

In this part of the experiment we ran the substance from week one through several tests to analyze our results. Using directions from step one and two, we weighed the Ni-en complex from last week. After this, we weighed about 0.30g of the Ni-en for our own calculations. Once I had 0.3g I quantitatively transferred it to a Erlenmeyer flask. Once the substance had dissolved in 50mL of DI, water green indicator was added and, HCl was titrated into the liquid until the substance turned a light yellow color, as indicated by step 3. Following steps 4 through five I added 6mL of NH₄OH and heated the solution near boiling. While this occurred I add 30mL of 1% DMG while stirring. Using steps 6 and 7 in the lab manual, I pre-weighed a 100mL beaker with a filter paper inside. Once the solution had cooled I filtered the precipitate using the Buchner funnel and washed the Precipitate with ethanol. Once dry I put the precipitate in the 100mL and heated it in a drying oven. Once the substance heated for 20 minutes and had cooled I weighed the end results to make my calculations.

2.   Completed Data tables Parts 1 through 4 (from pages 30, 32, 33 and 34). Be sure to include your lab partner’s name during the synthesis steps, and title each table appropriately.

Tables 1+2:      Synthesis Calculations and Results of the Ni-en complex     partner (s): Matthew Dovel

Table 3: Analysis and Calculations of en by HCl Titration

Tables 4+ 5: Analysis and Calculations of Ni by DMG

3.   Completed Results tables Part 6 (from page 35).

Table 6: Analysis and Calculations of Hydrates in Ni-en complex

4.   Show the calculation to determine the moles of HCl that was added during the titration.

31.21mL HCl     1L / 1000mL= 0.00403mol HCl

5.   Show the calculation to determine the moles of ethylenediamine, en, in your Ni-en complex you analyzed. Be sure to include any appropriate chemical reactions that were used in the calculation.

en + 2HCl       H₂en²⁺  + 2Cl^–

0.00403mol HCl      1mol en/ 2mol HCl= 0.00201mol en
6.   Show the calculation to determine the grams of ethylenediamine in your Ni-en complex you analyzed.
0.00156mol en    60.10g en/ 1mol en= 0.121g en

7.   Starting with the mass of Ni(DMG)₂ (that is the red precipitate), show the calculation to obtain the moles of Ni²⁺ that is present in your Ni-en complex you analyzed. Be sure to include any appropriate chemical reactions that were used in the calculation.

Ni²⁺   + 2DMG^–          Ni(DMG)₂

0.231g Ni(DMG)_2­    1mol Ni(DMG)₂    1mol Ni²⁺/ 288.94g Ni(DMG)₂/ 1mol Ni(DMG)₂= 0.000799mol Ni²⁺

8.   Show the calculation to determine the grams of Ni²⁺ in your Ni-en complex you analyzed.

0.000799mol Ni²⁺    58.69g Ni²⁺/ 1mol Ni²⁺= 0.0469g Ni²⁺

9.   Show the calculation to determine the grams of sulfate, SO₄^2–, in your Ni-en complex you analyzed.

1mol Ni²⁺= 1mol SO₄^2-

0.000799mol Ni²⁺ = 0.000799mol SO₄^2-

0.000799mol SO₄^2-     96.06g SO₄^2-/ 1mol SO₄^2-= 0.0768g SO₄^2-

10.   Show the calculation to obtain sum of the en, Ni²⁺, and SO₄^2– masses in your Ni-en complex.

0.0768g SO₄^2- + 0.0469g Ni²⁺ + 0.121g en= 0.245g Ni²⁺, SO₄^2-, en
11.  Show the calculation to obtain the grams of water in your Ni-en complex you analyzed.

0.306g Ni²⁺, en, SO₄^2-, H₂O

-0.245g Ni²⁺, en, SO₄^2-

0.061g H₂O
12.  Show the calculation to determine the moles of water in your Ni-en complex you analyzed.

0.061g H₂O    1mol H₂O/ 18.015g H₂O= 0.0034mol H₂O

13.  Using the moles of each species in your Ni-en complex, show the calculations to determine the empirical formula for your Ni-en complex. Show how you determined ALL ratios and show the formula

0.0034mol H₂O/ 0.000799mol Ni²⁺ = 4.25 approximately=4 H₂O

0.000799mol Ni²⁺/ 0.000799mol Ni²⁺= 1 Ni²⁺

0.00201 en/ 0.000799mol Ni²⁺= 2.51 approximately= 3 en

NiSO₄    6H₂O+Yen        [(Ni)_x(en)_y(H₂O)_z](SO₄)_x+6-ZH₂O

Since ethylenediamine is a bidentate only three molecules are needed to complete each Nickel complex. Therefore, since there are 3 molecules of en then the Nickel complex is complete and the 4 hydrates are connected to the Sulfate.

NiSO₄    6H₂O + 3en             [Nien₃]SO₄    4H₂O +2H₂O

14.   Knowing your Ni-en complex’s empirical formula, write the overall balanced reaction that took place describing your synthesis.

NiSO₄    6H₂O + 3en             [Nien₃]SO₄    4H₂O +2H₂O

15.   Show the theoretical yield calculation for your Ni-en complex you synthesized.

(1.032g NiSO₄    6H_2­O + 3en      1mol NiSO₄    6H_2­­O/ 262.9g NiSO₄       6H_2­O + 3en)     (1mol [Ni(en)₃]SO₄     4H₂O/ 1mol NiSO₄)    407.11g [Ni(en)₃]SO₄    4H₂O/ 1mol [Ni(en)₃]SO₄  4H₂O= 1.598g    [Ni(en)₃]SO₄    4H₂O

16.   Show your percent yield calculation for your Ni-en complex you synthesized.

1.225g Ni-en/1.598g Ni-en     100= 76.66% yield

17.   Answer the following questions. Show all work!

1. Give the correct chemical formulas for the following:

a)  potassium chromate                       b) sulfurous acid                     c) ammonia
K₂CrO₄                                                                        H₂SO₃                                             NH₃

1. Determine the correct chemical names of the following species:
   a)  LiH                                                     b)  FeO                                    c)  MgSO₄

Lithium Hydride                                     Iron (II) Oxide                      magnesium sulfate

1. A lab student analyzed her nickel-en complex for ethylenediamine, en, content. A 0.499 g sample of the synthesized Ni-en complex was dissolved in about 50 mL of water and titrated with 0.175 M HCl (aq). Endpoint required 37.49 mL of the HCl (aq). What is the mass (in grams) of en in the Ni-en complex analyzed?

37.49mL HCl/1000= 0.03749L HCl

0.03749L      0.175M HCl= 0.00656mol HCl

0.00656mol HCl     1mol en/2mol HCl= 0.00328 mol en

0.00328 mol en     60.10g en/ 1mol en= 0.197g en

1. Continuing on with the analysis of the Ni-en complex as found in question #3, 40 mL of dimethylglyoxime, DMG, solution was added to the titrated nickel-en complex solution. The resulting beautiful red complex, Ni(DMG)₂ was collected by filtration and found to weigh 0.469 g. What is the mass (in grams) of Ni in the Ni-en complex analyzed?

0.469g Ni(DMG)₂    1mol Ni(DMG)₂/ 288.94g Ni(DMG)₂    1mol Ni²⁺/ 1mol Ni(DMG)₂= 0.00162mol Ni²⁺

0.00162mol Ni²⁺     58.69g Ni²⁺/ 1mol Ni²⁺=0.0951g Ni²⁺

1. Determine the empirical formula of the complex synthesized in questions #3 and #4 above.
   0.00162mol Ni²⁺= 0.00162mol SO₄

0.00162mol SO₄^2-     96.06g SO₄^2-/1mol SO₄^2-= 0.156g SO₄^2-
0.0951g Ni²⁺ + 0.197g en + 0.156g SO₄^2-=0.448g Ni²⁺,en, SO₄^2-

0.499g Ni-en

-0.448g Ni²⁺, en, SO₄^2-

0.051g H₂O

0.051g H₂O    1mol H_2­O/ 18.015g H₂O=0.0028mol H₂O

0.0028mol H₂O/0.00162mol Ni²=1.7 H₂O

0.00162mol Ni²⁺/0.00162mol Ni²⁺=1Ni²⁺

0.00162mol SO₄/0.00162mol Ni²⁺=1SO₄

0.00328 mol en/0.00162mol Ni²⁺=2.02 en

NiSO₄      6H₂O +2en           [Ni(en)₂(H₂O)₂]SO₄ + 4H₂O