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GOAL/PURPOSE:
    to reinforce understanding of the role of limiting  reagent in a chemical reaction and to allow  students to master laboratory skills

NEEDED PRIOR CONCEPTS

• balanced chemical reaction
• stoichiometry
• mole ratio
• limiting reagent

• reduction/oxidation
• single replacement reaction
• activity series of metals
• transition metal chemistry
• chemical and physical properties of atoms vs ions
• variable oxidation states
• qualitative analysis
• solubility product
• thermodynamics and spontaneity
• heterogeneous reactions
• galvanic vs electrolytic cells

• use of an analytical balance
• transfer of liquid
• pipetting
• decanting

Beginning students can perform this experiment after going through a unit on stoichiometry and limiting reagent and use this to reinforce the theoretical concepts with concrete examples   Advanced students can prepare for this experiment by completing a series of questions that tie in various concepts:

• reduction potentials of Cu and Ag+
• prediction of the possible oxidation states of  copper ion
• determination of electrochemical potential of  the reaction between Cu and Ag+
• prediction of the products for the reaction
• calculation of the Gibbs free energy for the reaction
• definition of a heterogeneous reaction and the role of surface area in the reaction rate
• determination of oxidizing/reducing agents

• Nature: aging, spoiling, photosynthesis, vision,  rusting
• Industry: purification of metals, photography, metal plating

• warn students about AgN0₃ staining clothes and body --use gloves and wear appropriate clothing for the  experiment
• remind students not to dump waste down the drain --use waste container
• acetone is a highly volatile liquid   -- be sure to air dry first

 Step #2: show video on rolling Cu wire
         #4: show video on use of analytical balance
         #7: show video on use of pipette and pipette pump
         #8: caution students not to shake to the tube frequently--allow silver to grow on the copper wire to obtain
                larger precipitate
         #9: cross-out the words "pre-weighed" & show video on decanting
         #14: warn students to air dry first before placing it  in sand bath

DIRECTIONS:
        PLACE THE LETTER OF THE ANSWER THAT BEST COMPLETES EACH STATEMENT IN THE BLANK TO THE LEFT.

Use the data below for questions 1 -5.
 

1. The mass of AgNO3 reacted is __________.

  a.  1.640 grams               c.  0.300 grams
  b.  87.173 grams            d.  1.020 grams

2. The moles of AgNO3 (170 grams/mole) reacted is ____________.

  a.  0.0941 mole              c.  0.0018 mole
  b.  0.513 mole               d.  0.00965 mole

3. The mass of copper reacted is ___________.

  a.  l.600 grams               c.  0.300 grams
  b.  87.170 grams           d.  1 .200 grams

4. The moles of copper (atomic mass 63.5 grams/mole) reacted is ________.

  a.  0.0285 moles Cu       c.  0.00472 moles Cu
  b. 1.373 moles Cu          d.  0.0161 moles Cu

5.  Based on your answers to questions 1 through 4 and the remaining data, the balanced equation should be _______________________________.

   a.  AgNO₃ + Cu  ¾®  Ag + CuNO₃
   b.  AgNO₃ + 2Cu ¾®  Ag + Cu₂NO₃
   c.  2AgNO₃ + 2Cu ¾®  2Ag + 2CuNO₃
   d.  2AgNO₃ + Cu  ¾® 2Ag + Cu(NO₃)₂

 (Group work after lab is turned in to teacher)

1. Explain why acetone is used as the final rinse for both the Cu wire  and the Ag crystals.
 
 
 

2. What is the color of the copper nitrate solution ?    ____________________________
  Observe the tubes of the soluble copper compounds on the counter, CuCl₂ & CuSO₄.
  State a hypothesis about the color of soluble copper compounds
 
 
 

 3. You would not have seen a dielectric effect with the silver crystals and glass beaker unless you used rubber gloves.  Why?
 
 
 
 

 4. Look up the definition of the dielectric effect in a general science dictionary or physical chemistry book.  Please write the definition.
 
 

 5. Review your chapter on stoichiometry including Dalton's and Proust's laws.  Now explain why your answers are NO in questions # 3 & 4 in the LAB WRITEUP.
 
 
 

 6. If you wanted to conduct a theoretically complete reaction with the 10 cm of Cu wire, how much silver nitrate would you actually need?  (show balanced formula and dimensional analysis calculations)
 
 
 
 
 

 7. In the real world of both life and work why is it essential to calculate problems concerning limited reagents?
 
 
 
 

 8. If 80 grams of ammonium phosphide are added to 80 grams of sodium oxalate determine:

 a.  The balanced equation: __________________________________________________________________

 b.  The limiting reactant ___________________________________________________________________________

 c.  The moles of sodium phosphide produced __________________________________________________________

 d.  The grams of sodium phosphide produced __________________________________________________________

 e.  The moles of ammonium oxalate produced _________________________________________________________

 f.  The grams of ammonium oxalate produced _________________________________________________________

 g. Analyzing your data, what is your definition of a limiting reactant?  _________________________________________

  _____________________________________________________________________________________________

 _____________________________________________________________________________________________

  h. Calculate the moles and then the mass of the excess reactant.
 
 
 
 

 9. Name and describe the four major types of chemical stoichiometry you have or will be covering this quarter.