Experiment 12- Copper Reactions PDF

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Experiment 12: Copper Reactions Required reading: Ebbing, 11th Edition Chapters 3 and 4. -Limiting reactant, percent yield -Types of reactions Learning Goals:  Observing different types of chemical reactions, classifying them and writing balanced equations.  Calculating % yield.  Writing molecular, complete and net ionic equations.  Using common lab techniques: vacuum filtration, quantitative transfer, separation, decantation, organizing data, recording observations of physical and chemical changes. Background information and theory: Copper is an element that can be found in nature in a variety of different compounds. The most common natural ore is the sulfide, known as chalcocite, Cu 2S. This mineral is an important source of copper metal because it is about 80% copper by weight. Copper has many important uses due to its chemical and physical properties. Copper is a good conductor of both heat and electricity; hence it can be found in electrical lines or on cooking pots. It is also used in brass and bronze as an alloying agent. Copper oxides are bluish-green in color, making it a common material used for statues, roofs and patina metal siding on houses. Some colorful aqueous copper (II) complexes will be observed in today’s experiment. Chemists use sequences of chemical reactions to obtain a desired product that cannot be prepared in a single step. In a sequence of reactions, the product of an initial reaction is used as a reactant in a second reaction. This process can be repeated until the desired product is obtained. Just as chemists classify matter based on properties, they also classify reactions based on how they proceed. Different reaction classifications are described in Table 1. A given reaction may belong to more than one category. For example, in the present reaction, copper ions will be transformed into copper metal using zinc metal. This reaction can be classified as a single displacement reaction, but it is also a redox reaction since the copper is gaining electrons from the zinc atoms to produce the copper atoms and zinc ions in solution. Table 1: Reaction Classifications Reaction Type Single displacement Double Displacement Decomposition Combustion Neutralization Oxidation/Reduction

Description One element replaces a second in a compound Cations and anions of two different molecules swap partners One substance breaks down into two or more simpler substances Reaction between oxygen and another substance, often evolving heat. combination of an acid and a base Reaction in which electrons are transferred between two or

(redox) Precipitation

more substances Reaction in which two soluble substances combine to form one or more insoluble substances.

SDS: (safety concerns) Nitric acid and sulfuric acid are corrosive and irritant. Skin contact may cause burns. Avoid contact with these substances. Due to the hazards related to these chemicals, this lab requires that you wear long pants and shoes that completely cover your skin. Aprons must be used in this lab to avoid contact of the chemicals with your clothes and always use special (thick) gloves when manipulating these substances. All the work must be done in the hood. Lab Reports:  A separate formal lab report will be assigned by your instructor for this experiment. You must complete the data pages and post lab questions as part of your formal report. Follow the guidelines at the end of this experiment. General Directions: During this experiment copper metal will be transformed into several copper-containing species until solid copper is recovered (Scheme 1). Scheme 1: The series of copper transformation reactions. Cu (s) + 4 HNO3 (aq)  Cu(NO3)2 (aq) +2NO2 (g) +2H2O (l) (Rxn 1) HNO3 (aq) + NaOH (aq)  H2O (l) + NaNO3 (aq) Cu(NO3)2 (aq) +2NaOH (aq)  Cu(OH)2 (s, blue) + 2NaNO3 (aq)

(Rxn 2a) (Rxn 2b)

Cu(OH)2 (s, blue) + heat  CuO (s, black) + H2O (g)

(Rxn 3)

CuO (s, black) + HCl (aq)  CuCl2 (aq, green) + H2O (l)

(Rxn 4)

CuCl2 (aq, green) +Zn (s)  Cu (s) + Zn2Cl (aq) HCl (aq) + Zn (s)  H2 (g) + Zn2Cl (aq)

(Rxn 5a) (Rxn 5b)

Copper metal will be dissolved in a redox reaction with nitric acid forming a light blue solution containing aqueous copper (II) ions ( Rxn 1). Once all the copper is dissolved, the excess nitric acid is neutralized using sodium hydroxide ( Rxn 2a). An excess of hydroxide is added, converting the aqueous copper (II) ions into solid Cu(OH) 2 through a precipitation reaction ( Rxn 2b). Heating of the precipitate in water decomposes the Cu(OH)2 into CuO, a black solid ( Rxn 3). Hydrochloric acid is then added to dissolve the copper oxide, forming a light blue solution of Cu(II) ions ( Rxn 4). Finally, zinc metal participates in a redox reaction with both the copper ions ( Rxn 5a ) and the excess hydrochloric acid ( Rxn 5b) to form solid copper metal and evolve hydrogen gas. Using the initial mass copper and the mass of recovered copper after Rxn 5 is complete, the percent recovered from this cycle of copper reactions can be calculated using the equation:

% Recovered = (Final Mass of Copper/Initial Mass of Copper)x100

Procedure: 1)Watch the following video: https://www.youtube.com/watch?v=tyrne4AFOvY 2)Complete the data pages as you watch the video. 3) Your instructor may ask you for a formal report. Specific guidelines for this report are at the end of this manuscript. Don’t forget to also submit your data pages and the postlab questions.

Name: ______Judy Pham______ Copper Reactions Data Collect the following information from the video and complete the calculations indicated below. 1) In the following table organize the experimental data from the video. Include two decimals for the volumes used. Data table Initial mass of copper (g)

0.49g

Volume of HNO3 (6M) (mL)

10ml

Volume of water (mL)

10ml

Volume of NaOH (6M) (mL)

20ml

Volume of HCl (3M) (mL)

20ml

Mass od Zn (g)

1g

Final mass of copper (recovered) (g)

0.46g

2) What was the brown gas observed in the video when HNO 3 was added to the initial copper sample? 

The brown gas is NO2.

3) According to the video, what color is the Cu(NO 3)2 in solution? 

Blue

4) In the video, after NaOH was added to the solution containing Cu(NO 3)2, red litmus paper turned blue. What does this indicate? 

That indicates that the solution is a base.

5) According to the video, what color is the Cu(OH) 2? 

Dark blue

6) According to the video, what color was the CuO formed after heating up the copper (II) hydroxide? 

Black

7) When Zinc powder was added to the solution: a) What was observed? 

There was immediate bubbling. b) Write the chemical reaction.



CuCl2 + Zn = ZnCl2 +Cu c) What type of reaction is this?



Single replacement

Name: __Judy Pham___ Copper Reactions Postlab questions: Your instructor may ask you to answer these in your lab notebook, or to answer directly on this page and turn it in, or to include these answers in a formal lab report. Follow your instructor’s directions. 1.

Write the molecular balanced equation for the dissolution of copper. 

2.

3Cu + 8HNO3  3Cu(NO3)2 + 2NO + 4H2O Write the complete ionic balanced equation for the dissolution of copper.

 3.

Cu + 4HNO3  Cu(NO3)2 + 2NO2 + 2H2O Write the net ionic balanced equation for the dissolution of copper.

 4.

Cu + 4H+ + 2NO3-  Cu2+ + 2NO2 + 2H2O What type of reaction is this?



Oxidation/reduction

5. Write the molecular balanced equation for the preparation of copper(II) hydroxide.  6.

CuSO4 + 2NaOH  Cu(OH2) + Na2SO4 Write the complete ionic balanced equation for the preparation of copper(II) hydroxide.

 7.

Cu2+ + SO24- + 2Na+ + 2OH-  Cu(OH2) + 2Na+ + SO24Write the net ionic balanced equation for the preparation of copper(II) hydroxide.

 8.

Cu2+ + 2OH-  Cu(OH2) What type of reaction is this?

 9.

Double replacement Write the molecular balanced equation for the conversion of copper(II) hydroxide to copper (II) oxide.



Cu(OH2)  CuO + H2O

10. Write the complete ionic balanced equation for the conversion of copper(II) hydroxide to copper (II) oxide. 

Cu(OH2)  CuO + H2O

11. Write the net ionic balanced equation for the conversion of copper(II) hydroxide to copper (II) oxide. 

Cu(OH2)  CuO + H2O

12. What type of reaction is this? 

Decomposition

13. Write the molecular balanced equation for the conversion of copper (II) oxide to copper (II) chloride. 

CuO + 2HCl  CuCl2 + H2O

14. Write the complete ionic balanced equation for the conversion of copper (II) oxide to copper (II) chloride. 

CuO + 2H+ + 2Cl-  Cu2+ + 2Cl- + H2O

15. Write the net ionic balanced equation for the conversion of copper (II) oxide to copper (II) chloride. 

CuO + 2H+  Cu2+ + H2O

16. What type of reaction is this? 

Double replacement

17. Write the molecular balanced equation for the recovering of copper metal.



CuCl2 + Zn  ZnCl2 +Cu

18. Write the complete ionic balanced equation for the recovering of copper metal.  Cu2+ + 2Cl- + Zn  Zn2+ + 2Cl- + Cu 19. Write the net ionic balanced equation for the recovering of copper metal. 

Cu2+ + Zn  Zn2+ + Cu

20. What type of reaction is this?



Single displacement



Calculate the % recovery of copper. Show your calculation. 0.46/0.49 = 93.88%

21.

Experiment 12; Copper reactions Final Lab Report Your last formal lab report in CHEM 1411 is a report which pulls together all the data from your Coper reactions lab in order to understand different reactions that copper can undergo. Follow the directions below for a formal lab report. The directions for this formal lab report include both “general directions” for formal lab reports and SPECIFIC directions for the Copper reactions experiment. Lab Report Format

For the Lab Report, use steps 1 through 10 below. EACH STEP IS A SEPARATE ITEM. EACH step should have its own section (with labels at the beginning of each section and spaces between each section.) The lab report is always written in the past, third person, passive. (i.e. “The sample was dried overnight.” “The mass was measured on a top-loading balance.” “Part 3 was repeated two days later.”)

STEP 1. The Stuff in the Front (including...)

 The title of the experiment. The title says what you did. It should be brief (aim for ten words or less) and describe the main point of the experiment. An example of a title would be: "Rate of Crystal Growth: Naphthalene". If you can, begin your title using a keyword rather than an article like 'The' or 'A'.  Your name and the names of any lab partners (if any).  Course (CHEM 1411 …) / Your instructor's name.  The date(s) the lab was done.

STEP 2. Introduction and Purpose

 The introduction explains the objectives or purpose of the lab. [In this case – to observe different reaction that copper can undergo].  An introduction should contain background information. [In this case, briefly explain about the types of reactions, physical and chemical changes].  In one sentence, summarize how the experiment was performed. [In this case – briefly describe the experimental setup shown in the video].  Next discuss the technique(s) used. [In this case, the video shows the use of different techniques; briefly describe the theory of each technique in the order you will present them in your report.]  In your introduction, state the findings of the experiment (one sentence), and list the (brief) conclusions of the lab (one sentence). [In this case, how the copper changes from reaction to reaction]. You might want to add a list of reactions performed in the introduction.  Do NOT plagiarize!!

STEP 3. Materials STEP 4.

This section is required for this report. List all the materials that were used according to the video. This section is required for this report. You should write it based on

Procedure

STEP 5. Data

STEP 6. Results

the steps shown in the video. Do not write this as a paragraph, instead, use bullets. Write it in such a way that someone can repeat the same experiment following your instructions. Do not copy the procedure from this lab manual, write your own. You don’t need to use past tense or third person for this section. This is the data you actually collected. You must add your handwritten data pages at the end of the report, that is the raw data. In this section you must rewrite important data from the experiment in a clean way. Tabular format works great. These are facts. Leave interpretation for another section. PICTURES can be added here or in the results section. [In this case, you collected different sets of data: how much of each reagent was used, what did you see?. Give the data tables names and numbers. Make sure you label the data tables (at the tops and sides). Make sure your numbers all have units and the correct number of sig. figs. Qualitative observations should be included as well as measured values.]

Description of what the data means. Were there problems? Include calculations here. Include well-labeled graphs here. [In this case, draw a diagram indicating the changes in copper. Be specific. What type of reaction occur on each step; what products were observed? What are the substances responsible for each color? You can add pictures here. Make sure you label your pictures and refer to them in the results or discussion session. STEP 7. The Data section contains numbers. The Results section contains Discussion any calculations you made based on those numbers. The Discussion and section can also include calculations, or interpretation of the data. Analysis This is also where you would discuss any mistakes you might have observed in the video while doing the lab. Are there improvements to the procedure that should be in the lab? Errors to be determined? STEP 8. This sums up what happened in the experiment. What does it all Conclusions mean? What did you learn? This is important, because it shows me if you understood the point of the experiment. STEP 9. This is a section in a formal lab report. But it is NOT required for this References report unless your instructor says otherwise. STEP 10. Include your answers for the postlab. You don’t need to type them Answers to again, just add a copy of your postlab paper at the end of your report. questions...