Chemistry and Zinc

Topics: Chemistry, Titration, Concentration Pages: 4 (933 words) Published: April 28, 2014

Pre Lab Experiment 8
DETERMINATION OF % COMPOSITION OF PENNIES USING REDOX AND DOUBLE DISPLACEMENT (PRECIPITATION) REACTIONS

Objectives:
1. Learn how to determinate the percent composition
2. Learn how to get the percent using oxidation reduction and double reactions 3. To become more familiar with the use titration techniques 4. To learn how to get the salt out of an quimical
Background:
To develop and utilize procedures to determine the percent composition, of ZnCI2. As well titrating with NaOH solution. After all the experiment we got hta salt witch we weighted and we got our results. Experiment reactions:

.33w of Zn(OH)2 x moles Zn(OH)2/m. moles Zn(OH2) x 1molZnCI2/1 mol Zn(OH)2 x g molZnCI2/1 mol of ZnCL2 = .4531 grams of ZnCI2 .4531g of ZnCl2 x 1 moles ZnCI2/m. moles ZnCI2 x 1molZn/1 mol of ZnCI2 x 65.39 of Zn/1 mol Zn = .2174g Zn Materials needed:

Scale
Burette
Beaker
Spatula
Erlenmeyer flask
Prenolpthen (color indicator)
ZnCL2
NaOH
Tube
Vacuum
Paper filters
Rubber base

Questions:
1. What is the weight of a post 1982 penny?
2.5 grams
2. What is the percent copper and zinc in a post 1982 penny? 97.5% of zinc and 2.5% of copper
3. How many grams of copper and zinc are in a post 1982 penny? 2.44grams of copper and 0.0625gramss of zinc
4. How many moles of copper and zinc are in post 1982 pennies? 0.0383moles of cooper and 0.000955moles of zinc
5. Write a balanced reaction of zinc with HCl.
Zn (s) + 2 HCl(aq) ====> Zn+2(aq) + 2 Cl-(aq) + H2(g)
Reaction:
Zn(s) + 2 H+(aq) ====> Zn+2(aq) + H2(g)
6. How many moles of HCl are needed to react completely with all of the zinc in a post 1982 penny?
7.46 x 10-2 mol HCl
7. In a procedure developed to determine the percent zinc in post 1982 pennies, 50 ml of an HCl solution was used to react (dissolve) all of the zinc in the penny. To ensure complete reaction, the solution contains twice as many moles of HCl that is actually needed. What...
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