Lab5c i need pre lab and post lab from document 5, now send me pre lab, when i get the data you do post lab. Identification of an Unknown Salt by Determina

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Identification of an Unknown Salt by Determination of the Percentage Copper

Introduction to Percent Composition:

1) Percent composition is defined as the mass percentages of each element in a compound.

2) The mass percentage of element A in a compound is equal to the parts of A per hundred parts of the total, by mass.

a. The equation is as follows: Mass % A = (Mass of A in the compound / Mass of the entire compound) X 100%.

3) An example calculation for nitrobenzene, C6H5NO2

a. Step 1: Determine the molar mass of nitrobenzene.

i. Molar mass = (6 x 12.011 g/mol) + (5 x 1.0079 g/mol) + (1 x 14.0067 g/mol) + (2 x 15.9994 g/mol) = 123.11 g/mol

b. Step 2: Calculate the percent composition for each element.

i. C: (72.066 g/mol / 123.11 g/mol) x 100% = 58.54%

ii. H: (5.0395 g/mol / 123.11 g/mol) x 100% = 4.09%

iii. N: (14.0067 g/mol / 123.11 g/mol) x 100% = 11.38%

iv. O: (31.9988 g/mol / 123.11 g/mol) x 100% = 25.99%

Introduction to the Reactivity Series:

1) A single displacement (single replacement) reaction occurs when an element reacts with a compound to displace an element from that compound.

a. Example #1: Zn(s) + 2AgNO3(aq) ( Zn(NO3)2(aq) + 2Ag(s)

b. Example #2: 2Al(s) + 6HCl(aq) ( 2AlCl3(aq) + 3H2(g)

2) Whether a reaction takes place depends on the relative reactivity of the elemental metal to the displaced element.

a. If the elemental metal is more reactive than the displaced element, then a reaction will take place.

b. If the elemental metal is less reactive than the displaced element, then a reaction will NOT take place.

3) The reactivity series provides a list of the common metals in order of decreasing reactivity (from the most reactive to the least.)

a. The reactivity series is as follows: Li, K, Ba, Ca, Na, Mg, Al, Zn, Cr, Fe, Cd, Co, Ni, Sn, Pb, H2, Cu, Hg, Ag, Au

4) The reactivity series also reveals which elements react with water and/or acids to produce hydrogen gas.

a. Metals lithium to sodium (Li–Na) react violently with liquid water (and acid) to produce hydrogen gas.

b. Metals magnesium to cadmium (Mg–Cd) react slowly with liquid water but considerably with acids to produce hydrogen gas.

c. Metals cobalt to lead (Co–Pb) do NOT react with liquid water but considerably with acids to produce hydrogen gas.

d. Metals copper to gold (Cu–Au) react neither with liquid water nor acids.

The Copper Salts*:

1) Cu3(PO4)2 • 3H2O

2) CuCl2 • 2H2O

3) CuSO4 • 5H2O

4) Cu(ClO4)2 • 6H2O

5) CuSeO4 • 5H2O

6) Cu(CH3CO2)2 • H2O

Substances to include in the Table of Chemical and Physical Properties:

Prepare this table and all the compounds used in the experiment and complete the data table “Percent Copper in the Reactants”.

Procedure:

1) On an analytical balance, weigh out 1.0 grams of the unknown copper salt in a weigh boat or on a piece of weigh paper.

a. Record the unknown number/letter and the color of the salt in your lab notebook.

b. Record the mass in your lab notebook.

2) Transfer the unknown copper salt into a 100 mL beaker.

a. Ensure all powder is in the beaker; avoid spilling.

b. If material clings to weigh boat, transfer into the beaker using the deionized water in the next step.

3) Using a 100 mL graduated cylinder, obtain 30.0 mL of deionized water and add to the beaker containing the unknown copper salt.

4) Place beaker onto a hot plate.

5) Gently heat the solution to dissolve salt.

a. Stir with a glass stir rod until dissolved.

b. Do NOT allow for a significant boil.

6) Weigh out 1.0 grams of mossy zinc and cautiously add to the solution.

a. Do NOT allow any of the liquid material to splash out.

7) Continue heating the solution using a stirring rod to mix thoroughly.

a. Do NOT allow for a significant boil.

b. Do NOT remove the stirring rod from the beaker; some of the copper solution will cling to the glass.

8) Continue stirring the heated solution until the solution color completely fades.

a. Add an additional 0.3 g of mossy zinc if all zinc reacts and the color remains.

9) Once the solution is completely colorless, discontinue heating and allow to cool for a few minutes.

10) Obtain 5.0 mL of 6.0 M sulfuric acid.

11) After cooling for a few minutes, slowly add the sulfuric acid to the solution 0.5 mL at a time.

a. This addition step should take at least 5 minutes.

b. This step is to remove unreacted zinc.

12) A few minutes after this addition, remove all chunks of unreacted zinc with forceps.

a. Be careful to rinse off all bits of zinc with deionized water before removing from the solution.

13) Obtain a piece of filter paper and a watch glass and record the mass on an analytical balance.

14) Create a cone with the filter paper by folding it in half twice to form a quarter of a circle and then separating one side from the other three.

15) Place filter paper into a glass filter and then place filter onto a 500 mL or smaller Erlenmeyer flask.

16) Wet the filter with a small amount of deionized water.

a. Ensure that you remove the bubbles between the filter paper and funnel.

17) Once the filter paper is secure, transfer the contents of the beaker into the filter paper.

a. The water should pass through the filter leaving behind the copper.

b. Do not allow the liquid volume to exceed the height of the filter paper.

c. Ensure all copper is collected in the filter.

18) Use the glass rod to assist the transfer into the filter paper.

19) Add 1.5 mL of 6M sulfuric acid to approximately 15.0 mL of deionized water and rinse collected copper.

a. This step is necessary to ensure zinc has been eliminated.

20) Following the addition of the acid rinse, wash thoroughly with copious amounts of deionized water.

a. If some acid remains, the filter paper will burn in the oven.

b. Ensure the filter paper is free from acid.

21) After the filter paper has drained from the last rinse, transfer filter paper with contents onto the pre–weighed watch glass.

22) Place sample into a steam bath (boil 30 mL of water in a 100 mL beaker using hot plate).

a. Allow at least 20 minutes to ensure dryness.

23) Once dry, carefully remove from the oven and allow to cool to room temperature.

24) Once cool, obtain the mass of the sample.

Clean – Up:

25) Rinse all filtrates down the sink with plenty of water.

26) All copper and unreacted zinc should be placed in the appropriate waste containers.

Sample Data Table for Percent Copper in Reactants:

No.

Formula of Copper Salt

IUPAC Name

Molar Mass

(g/mol)

Percent Copper

1

Cu3(PO4)2 • 3H2O

2

CuCl2 • 2H2O

3

CuSO4 • 5H2O

4

Cu(ClO4)2 • 6H2O

5

CuSeO4 • 5H2O

6

Cu(CH3CO2)2 • H2O

Sample Data Table:

a) Unknown number/letter of copper salt: ________

b) Mass of unknown copper salt in grams: ________

c) Mass of mossy zinc in grams: ________

d) Mass of watch glass + filter paper in grams: ________

e) Mass of watch glass + filter paper + copper in grams: ________

f) Mass of copper in grams (e – d): ________

g) Experimental percent copper in salt (f/b X 100%): __________

h) Identity of copper salt based on percent copper: ________

i) Balanced equation for the reaction: _____________________________

j) Balanced equation for zinc elimination: __________________________

Banerjee

General Chemistry-I Lab

*Notice all solid copper salts are available as hydrates. When dissolved in water, they are no longer hydrates.

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