Reactions of Copper Lab Report

Reactions of Copper

Objectives:

  • The purpose of this experiment is to demonstrate a cycle of reactions involving copper.
  • A specific quantity of copper will be transformed through a series of reactions and then recovered as solid copper.
  • A percent recovery will be calculated and sources of loss (or gain) will be identified.

Introduction:

In this experiment you will carry out several reactions starting with solid copper wire, you will transform the copper into soluble and insoluble copper salts and the back again to solid copper metal.

The cycle of copper is summarized in the following equation:

Cu (s) → Cu(NO3)2 (aq) → Cu(OH)2 (s) → CuCl2 (aq) → Cu(s)

Part A: Copper (II) nitrate from copper

The nitrate ion oxidizes the copper metal to Cu (II) ions while itself being transformed to NO2 gas in the process. This is an example of a reaction called an oxidation reduction reaction, in these types of reactions one reactant is oxidized by losing one or more electrons and one reactant is reduced by gaining electrons. The physical change you should observe is the copper-colored metal vanishing as the solution turns blue and an orange gas evolving from the reaction mixture.

3Cu (s) + 8HNO3 (aq) → 3Cu(NO3)2 (aq) + 2 NO2 (g) + 4H2O (Reaction 1)

Part B: Copper (II) hydroxide is formed from copper (II) nitrate

In this step 2 reactions are occurring, copper (II) nitrate reacts with sodium hydroxide to produce copper (II) hydroxide, an insoluble blue solid. This reaction is called a precipitation reaction. A precipitation reaction occurs when a solution containing a specific cation is mixed with a solution that contains a specific type of anion (at a concentration above a specific threshold) that produces an insoluble solid. For example, in this reaction Cu2+ ions combine with OH ions to produce insoluble Cu(OH)2 .

Cu(NO3)2 (aq) + 2NaOH (NaOH) → Cu(OH)2 (s)+ 2 NaNO3 (aq) (Reaction 2)

The second reaction that is occurring is the neutralization of the excess nitric acid used in part A, the nitric acid reacts with sodium hydroxide to produce soluble sodium nitrate and water.

HNO3 (aq) + NaOH (aq) → NaNO3 (aq) + H2O (l) (Reaction 3)

Part C: Copper (II) chloride is formed from copper (II) hydroxide

The reaction between copper hydroxide and hydrochloric acid is another neutralization reaction the copper (II) hydroxide acts as a base and the hydrochloric acid functions as the acid, the products of this reaction are a salt (CuCl2) and water.

Cu(OH)2(s) + 2HCl(aq) → CuCl2(aq) + 2H2O (l) (Reaction 4)

Part D

There are 2 reactions occurring in this step of the reaction sequence. The reaction of the copper II ion from copper (II) chloride reacting with zinc is another example of an oxidation reduction reaction. You will observe the blue copper (II) ion solution gradually become a colorless solution as the zinc II ions replace the blue copper II ions in solution and the solid copper forms. The zinc metal is giving up two electrons to the copper II ions. The zinc is being oxidized and the copper II is being reduced.

CuCl2 (aq)+ Zn (s) → Cu (s) + ZnCl2(aq) (Reaction 5)

The second reaction is the reaction of the excess hydrochloric acid reacting with zinc to form hydrogen gas and zinc chloride. This is also an oxidation reduction reaction.

Zn (s) + HCl (aq) → H2(g) + ZnCl2 (aq) (Reaction 6)

Safety:

Wear safety goggles at all times. Wear gloves when handling chemicals during this experiment. Do not touch hot glassware with your hands use tongs or a silicone mitt. Nitric acid or Hydrochloric acid: cover spills with sodium carbonate to neutralize the acid, then transfer to a container and carefully dilute with water followed by pouring down the drain with more water.

Equipment/Supplies:

  • Copper wire (~0.35 g)
  • Concentrated nitric acid (3 mL)
  • 6 M sodium hydroxide (~20 mL)
  • 6 M Hydrochloric (~10 mL)
  • Sandpaper
  • Funnel
  • Filter paper
  • Hot plate
  • Red litmus paper
  • 500 mL Erlenmeyer filter flasks
  • Evaporating dish
  • Glass stirring rod
  • Funnel stand
  • 250 mL Erlenmeyer flask
  • Buchner Funnel
  • Neoprene adapter
  • Vacuum tubing
  • 250 mL Beaker (2)

Procedure:

Part A: Copper (II) nitrate from copper

  1. Clean a ~0.5 cm piece of copper wire with sandpaper, cut the wire so that it has a mass between 0.3- 0.4 grams.
  2. Tare a 250 mL beaker using a top loading balance.
  3. Place the copper wire into the 250 mL beaker, record the mass of the copper wire to 3 decimal places.
  4. Transport the beaker with the copper wire to the fume hood.
  5. Caution: Concentrated nitric acid is very corrosive and toxic. Wear gloves when handling the nitric acid. In the fume hood add 3 mL of concentrated nitric acid to the copper wire. Observe the color of the gas formed, gently swirl the beaker.
  6. If gas evolution has completed and some copper wire remains add 2-3 drops of nitric acid to the mixture.
  7. Once gas evolution has completed and the solid copper has reacted completely return to the lab bench with your reaction mixture.
  8. Slowly add 10 mL of distilled water to the reaction mixture.

Part B: Copper (II) hydroxide is formed from copper (II) nitrate

  1. Add 6 M sodium hydroxide (NaOH) dropwise to the reaction mixture in the 250 mL beaker, constantly stirring with a glass stirring rod as you add the sodium hydroxide.
  2. Obtain a piece of red litmus paper. Touch the piece of red litmus paper with the glass stir rod used to stir the reaction mixture, if the red litmus paper remains red, continue adding 6 M sodium hydroxide to the reaction mixture dropwise until the solution is basic and turns the red litmus paper blue
  3. Add approximately 25 mL of distilled water to the reaction mixture
  4. Filter the blue precipitate by gravity filtration following these steps:
    1. Fold an 11 cm piece of filter paper in half twice as shown below.

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    1. Assemble the apparatus for gravity filtration: Clamp an iron ring to a ring stand, set a wire triangle on top of the iron ring, insert a funnel into the funnel stand, insert the filter paper into the funnel. Place a 250 mL Erlenmeyer flask under the funnel.

Gravity Filtration apparatus

word image 186

    1. Wet the filter paper with distilled water from your water wash bottle. Carefully pour the reaction mixture into the funnel using a stir rod as a guide.
    2. Rinse the blue solid with distilled water with the wash bottle

Clean up: Transfer the filtrate collected in the Erlenmeyer filter flask to the hazardous “Discarded Filtrates” waste jar located in the fume hood. DO NOT POUR THIS DOWN THE DRAIN!

Part C: Copper (II) chloride is formed from copper (II) hydroxide

  1. Place a clean 250 mL beaker under the funnel containing your solid reaction residue.
  2. Measure 10 mL of 6 M hydrochloric acid. Using a pipette rinse the blue solid in the funnel with approximately 10 mL of 6 M Hydrochloric acid. If all the copper (II) hydroxide did not dissolve, then repeat this step with more HCl until there is no more blue residue on the filter paper.
  3. Rinse the filter paper with distilled water to remove the last traces of the copper II chloride solution from the filter paper

Clean up: Transfer the used filter paper to the “Filter paper waste bucket” located in the fume hood

Part D: Zinc reduces copper (II) ions to copper

  1. Weigh approximately 2 g of zinc powder, Zinc Shot, or (~ 1 g of Magnesium into a weigh boat.
  2. Add the zinc or magnesium to the reaction mixture. Observe the brown copper solid form and gas evolution.
  3. If any blue color remains after the zinc (or magnesium) has completed reacting (bubbling has stopped, or all of the zinc or magnesium has dissolved) add a rice size portion of zinc (or magnesium) to the mixture.
  4. Label a crystallizing dish with your name and “copper”. Weigh the crystallizing dish and a (40 mm ??) piece of filter paper together. Record the mass on your datasheet.
  5. Once the reaction mixture is completely colorless, and all the zinc (or magnesium) has been consumed, assemble the apparatus for vacuum filtration as shown below.

Vacuum filtration apparatus

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  1. Insert the pre-weighed piece of filter paper into the Buchner funnel, turn on the water then wet the filter paper with distilled water.
  2. Pour your reaction mixture into the Buchner funnel, rinse the beaker with the wash bottle to remove any traces of coper from the beaker.
  3. Rinse the solid copper with distilled water.
  4. Carefully transfer the copper and filter paper to an evaporating dish.
  5. Transfer the filtrate to the hazardous waste container.
  6. Transfer the crystallizing dish and copper to a drying oven and allow the copper to dry. Once the copper is dry remove the crystallizing dish from the oven and set it to cool on a ring stand or a tile and allow to cool to room temperature.
    1. (Alternatively, your instructor may ask you to allow your copper to dry until the next lab meeting in the fume hood, place your labeled crystallizing dish in the bin in the fume hood labeled with your course and section)
  7. Measure the mass of the copper, filter paper, and crystallizing dish, record the mass on your datasheet.

Clean up- discard the copper into the hazardous waste container designated for recovered copper waste.

Name: _____________________________________ Date: ______________

Post-Lab:

  1. The atomic mass of Cu is 63.54 g/mol, calculate the moles of copper of copper in 0.350 grams of copper wire.
  2. This problem refers to Reaction 1.
    1. The nitric acid you used has a concentration of 16 moles per liter, If you added 3.0 mL of this acid to your beaker, calculate the moles HNO3 in 3.0 mL of 16 M HNO3.
    2. How much HNO3 (in moles) reacted with your wire?
    3. How much HNO3 (moles) remains unreacted with Cu(s)?
    4. Theoretically, how much Cu(NO3)2 is produced from the reaction?
  3. This question refers to part B
    1. . How much NaOH (in moles) is needed to neutralize the excess nitric acid?
    2. How many moles of NaOH is needed to convert copper (II) nitrate to copper (II) hydroxide in Reaction 3?
    3. The NaOH solution contains 6 moles per liter (6.0 M NaOH). What volume is needed to provide the total quantity calculated of NaOH needed in part B?
    4. Suppose you add just enough NaOH so that all the Cu(NO3)2 is converted to solid Cu(OH)2 by Reaction 3 and all the remaining HNO3 is neutralized in Reaction 4. How much Cu(OH)2 is produced?
  4. The questions refer to part C
    1. How much HCl (in moles) is needed to dissolve all the solid Cu(OH)2 in part C?
    2. The HCl solution concentration is 6.0 moles per liter (6.0 M HCl). What volume is required to convert copper (II) hydroxide to copper (II) chloride?
    3. Theoretically how much ( in moles) of CuCl2 is produced?
  5. These questions are related to part D
    1. Suppose that you weighed out 2.0 grams of zinc metal (65.4 g/mol). Calculate the moles of Zinc
    2. If the zinc is in excess, how much copper metal (in moles) is produced?
    3. What is theoretical mass in grams of Cu metal that can be produced?
  6. What is the formula for percent yield? Calculate the percent yield of copper produced from your reaction.
  7. List 2 sources of error that could have resulted in higher than expected yields of copper.
  8. List 2 sources of error that could have resulted in lower than expected yields of copper.

Name: __________________________________ Date: _____________

Data Sheet:

Part A. Copper to copper nitrate

mass copper wire ___________________________ g

Reaction observations:

Part D. Copper sulfate to copper

mass of crystallizing dish and filter paper ___________________________ g

mass of recovered copper ___________________________ g

Percent of copper recovered ___________________________ %

Show percent copper recovered calculations:

Name: _______________________________________ Date: _____________

Pre-Lab:

  1. For each of the following reactions write the complete ionic, and net ionic reaction for the following reactions:
      1. 3Cu (s) + 8HNO3 (aq) → 3Cu(NO3)2 (aq) + 2NO (g) + 4H2O (l)

Reaction classification _________________________

Complete ionic

Net ionic

      1. Cu(NO3)2 (aq) + 2 NaOH (aq) → Cu(OH)2 (s) + 2 NaNO3 (aq)

Complete ionic

Net ionic

      1. HNO3 (aq) + NaOH (aq) → NaNO3 (aq) + H2O

Complete ionic

Net ionic

      1. Cu(OH)2 (s) + 2HCl (aq) → CuCl2 (aq) + 2H2O (l)

Complete ionic

Net ionic

      1. CuCl2 (aq) + Zn (s) → Cu (s) + ZnCl2 (aq)

Complete ionic

Net ionic

      1. Zn (s) + 2HCl (aq) → H2 (g) + ZnCl2 (aq)

Complete ionic

Net ionic

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