Download Experiment: Cycle of Copper Reactions and more Lab Reports Chemistry in PDF only on Docsity!
RREEAACCTTIIOONNSS^ OOFF^ CCOOPPPPEERR
Copper will undergo many types of reactions. In this experiment you will observe a sequence of copper reactions. The sequence begins with copper metal and ends with copper metal, so it is called a cycle of copper reactions. Observations will be made for each reaction. Since no copper is added or removed between the initial and final reaction steps, copper can be quantitatively recovered. In other words to recover the same amount of copper metal that you started with, this will require careful work. The success of the copper metal recovery will be shown by calculating the percent yield. The diagram below shows (in an abbreviated form) the cycle of copper reactions.
The following are the completed but unbalanced equations. Each equation is numbered to match each step of the cycle:
I. HNO 3 (aq) + Cu(s) Cu(NO 3 ) 2 (aq) + H 2 O(l) + NO 2 (g) (oxidation-
reduction reaction)
II Cu(NO 3 ) 2 (aq) + NaOH(aq) Cu(OH) 2 (s) + NaNO 3 (aq)
III. Cu(OH) 2 (s) CuO(s) + H 2 O(l)
IV. CuO(s) + H 2 SO 4 (aq) CuSO 4 (aq) + H 2 O(l)
V. CuSO 4 (aq) + Al(s) Al 2 (SO 4 ) 3 (aq) + Cu(s)
It is useful to classify reactions into different types, because products of reactions can then be predicted. No one classification scheme can accommodate all known reactions but you will classify the reactions in your experiment based on ideas of double exchange, combination, decomposition, and replacement.
Throughout the experiment careful observations and recordings must be made. Determine the colors of the solids as well as the color of ions in solution. In order to have a good percent yield, it is important to prevent loss by avoiding spattering while boiling, leaving product on sides of beakers, and spilling of product. Purify precipitates by washing efficiently and then drying completely before weighing.
- Safety goggles must be worn at all times
- Concentrated nitric acid, HNO 3 , is hazardous. It produces severe burns on the skin and the vapor is a lung irritant. Any acid spilled on the skin or splashed into your eyes must be rinsed with a large volume of water for 15 minutes. While handling nitric acid you must wear gloves. Rinse your hands with tap water after handling HNO (^) 3.
- NaOH solutions are corrosive to the skin.
- Dissolution of the copper wire with concentrated HNO 3 should be carried out in the fume hood. The brown NO 2 gas that is evolved is very irritating to the lungs.
- Dilute hydrochloric acid (HCl) and sulfuric acid (H 2 SO 4 ) can harm eyes, skin, and clothing. Handle with care. Any acid spilled on the skin or splashed into your eyes must be rinsed with a large volume of water.
PPRROOCCEEDDUURREE
Day 1
Remember: [DO NOT PUT ANY EXCESS REAGENTS BACK INTO THE REAGENT
BOTTLES!]
Step I
- Weigh a clean and dry evaporating dish to the nearest .1 mg. Record the mass on the data sheet (Page 5)
- Obtain a piece of copper. Weigh the copper plus an evaporating dish to the nearest 0. milligram, recording the mass on the data sheet (page 5)
- Place the copper into a 250 mL beaker; and place it under the fume hood. Your instructor will
put on a pair of rubber gloves and will carefully add 4.0 ml of 16M nitric acid, HNO 3 concentrated.
- Record your observations on the report sheet, page5. After the copper has dissolved swirl the solution to remove the brown NO 2 gas (What is in the solution when the reaction is complete?).
- After the copper has dissolved, carefully (slowly!) add approximately 100 ml distilled water to your copper solution.
- Make and record your observations on page 5
Step II (Conducted at your lab bench)
- While stirring the solution with a glass rod, slowly add 15 mL of Dil (6 M) NaOH to precipitate Cu(OH) 2. It is important to add the NaOH slowly, because you are adding a base to an acid. (This
type of reaction generates a lot of heat). If your mixture warms up too much, you will skip step II and form the CuO directly-Step III.)
- Start to preheat hot plates
- The solution should be alkaline (basic) after the addition. A drop of solution touched to red litmus paper turns it blue. If the solution is not basic, add an additional 5 mLs of NaOH. Wait until the precipitate settles slightly and look at the clear top part of the mixture. There should be no blue color left in the top clear liquid, the solution). (What ion gives the blue color?)
- Record your observations -2-
Step III
- Heat the Cu(OH) 2 solution just barely to the boiling point using a hot-plates , while stirring continuously gently with a glass rod to prevent "bumping" (a phenomenon caused by the formation of a large steam bubble in a locally overheated area of the beaker)
- Continue to heat gently while stirring to better coagulate the CuO.
Report Sheet Name____________
Last First
Instructor’s initial_________
Experiment: Reactions of Copper
DATA AND CALCULATIONS
- Mass of the empty evaporating dish ______________________
- Initial mass of copper wire plus the evaporating dish _____________________
Data approval_____________
- Calculate initial mass of Copper wire
Setup:
____________________
- Final mass of recovered copper
Mass of evaporating dish plus dry copper #1 ______________________
#2 ______________________
#3 ______________________
Data approval_____________
- Mass of recovered copper ______________________ Setup:
6 Percentage recovery (show calculations) Setup:
___________________
EQUATIONS AND OBSERVATIONS
For each step of the cycle, write the products of the reaction, balance the chemical equations, and write physical states. Classify each reaction. Also, record your observations of what happens at each step and answer the questions posed earlier in the Experimental Procedure.
STEP I
Cu + HNO 3
What ions are in the solution after the reaction is complete? __________________
Observations:
Data approval_____________
STEP V
Al + CuSO 4
Reaction type ______________________
Al + H 2 SO 4
Reaction type ______________________
Al + HCl
Reaction type ______________________
Observations:
What gas is produced in the reaction?_______________
What ions are removed by the washing and decantation near the end of STEP V?
____________________________________
What is the color of recovered copper?______________
Data approval_____________
QUESTIONS:
- Give possible reasons why the percentage recovery might be low.
a.
b.
c.
- Give possible reasons why the percentage recovery might be over 100%.
a.
b.
c.
- How many milliliters of 3.0 M NaOH are required to react with 4.0 mL of 16.0 M HNO 3?
Equation:
Answer__________________
- How many milliliters of 3.0 M NaOH are required to react with 0.50 g of Cu2+^ to form Cu(OH) 2?
Equation:
Answer__________________
- What is the theoretical percentage copper in Cu(OH) 2?
Setup:
Answer__________________
- What theoretical weight of CuO can be obtained from 2.00 g of Cu?
Setup:
Answer__________________
- Iron is obtained from iron ore according to the following reaction:
Fe 2 O 3 + 3 CO 2 Fe + 3 CO 2 (unbalanced) a. Assuming the blast furnace is 90.0 % efficient in recovering the iron, what is the actual mass of iron obtainable from a ton of ore?
1 ton = 2000.0 lb 1 lb = 453.6 g
Answer_____________
-8-
Problem #7 continued
b. What is theoretical yield of iron if 200.0 g of Fe 2 O 3 reacts with 100.0 g of CO?
