Reactions of Copper Lab Report Sheet

Objectives:

1. To observe the reactions of copper and its compounds

2. To calculate the percent recovery of copper undergoing a series of reactions

CHEM 1411 Alternate Reactions of Copper Lab

CHEM 1411 Reactions of Copper Lab

Materials:

Dallas College CHEM 1411 Alternate Reactions of Copper Lab p. 2 May 2021

· Graduated cylinders

· Beakers

· Cu wire

· Zn metal

· Concentrated HNO3

· Acetone

· 3 M NaOH

· 6 M H2SO4

· Deionized water

· Hot plate

Introduction:

In general, there are five types of chemical reactions:

1. Combustion

2. Combination

3. Decomposition

4. Single displacement

5. Double displacement (or exchange, metathesis)

This lab will illustrate decomposition, single displacement and double displacement reactions by taking copper through a series of reactions which will ultimately regenerate solid copper metal.

Let’s learn a bit about these reaction types so that we can understand what happens to our copper during the course of this experiment.

Single displacement reactions are also examples of oxidation-reduction or Redox reactions. In redox reactions, electrons are transferred from one reactant (reducing agent) to another reactant (oxidizing agent). The reducing agent loses electrons and is oxidized. The oxidizing agent gains electrons and is reduced.

The reaction of metallic zinc with silver ion is an example of a single displacement redox reaction. Below shows the net ionic equation:

Zn (s) + 2Ag+(aq) → Zn2+(aq) + 2Ag(s)

Zinc metal (Zn) loses electrons so it is oxidized, and is the reducing agent. Silver ion (Ag+) gains electrons so it is reduced, and is the oxidizing agent.

Metals can also react with acids to produce a salt and hydrogen gas. This reaction is also a single displacement and redox reaction.

Molecular Equation: Zn (s) + 2HCl (aq) → ZnCl2 (aq) + H2 (g)

Complete Ionic Equation: Zn (s) + 2H+ (aq) + 2Cl − (aq) → Zn2+ (aq) + 2Cl − (aq) + H2 (g)

Net Ionic Equation: Zn (s) + 2H+ (aq) → Zn2+ (aq) + H2 (g)

Not all metals react with acids as in the reaction with zinc. In the reaction with zinc shown above, we see that zinc is replacing the hydrogen ion of hydrochloric acid. This means that Zn is more reactive than H+ since it replaces H+ in the compound. We can see this from the activity series. Below is the activity series with Li being the most reactive.

Li>K>Ba>Ca>Na>Mg>Al>Mn>Zn>Cr>Fe>Co>Ni>Sn>Pb>H2>Cu>Ag>Hg>Pt>Au

Copper, silver, mercury, platinum, and gold show no reaction with hydrochloric acid. These metals are less reactive than H+ and are not oxidized by the H+ in the compound. Copper shows no reaction with hydrochloric or sulfuric acid.

However, it does react with nitric acid, HNO3. Copper and nitric acid produce a caustic poisonous brownish NO2 gas. This is not the same simple single displacement reactions as in with zinc. When Cu reacts with nitric acid, the oxidizing agent is the nitrate ion and not the hydrogen ion. Remember that copper shows no reaction with the hydrogen ion since it is less reactive according to the activity series. The reaction below shows the oxidation of copper by concentrated nitric acid to produce the copper(II) ion:

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

brownish

The Cu(NO3)2 product then reacts with NaOH to give insoluble Cu(OH)2. This is a double displacement reaction:

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

Upon heating, the Cu(OH)2 is dehydrated to produce solid CuO. This is an example of a decomposition reaction:

Cu(OH)2 (s) + heat → CuO (s) + H2O (g) Reaction 3

black

When black CuO is allowed to react with sulfuric acid in an exchange reaction (or double displacement), copper(II) sulfate is produced:

CuO (s) + 2H2SO4 (aq) → CuSO4 (aq) + H2O (l) Reaction 4

black blue

Finally, copper metal can be recovered in this “loop” of reactions by reacting copper(II) sulfate with zinc metal in a single displacement redox reaction.

CuSO4 (aq) + Zn(s) → ZnSO4 (aq) + Cu(s) Reaction 5

Recall that any metal element will replace another metal in a compound if the metal element is more reactive in the activity series. Note that zinc is more reactive than copper on the activity series and therefore, will replace copper in the compound.

In this experiment, you will carry out five successive reactions starting with copper wire and ending up with solid copper. In each reaction, copper (or one of its compounds) will react with various reagents. You will calculate the percent recovery of copper by comparing how much copper you start and end with.

You will also be asked to record your observations of the chemical reactions that occur. Evidence of chemical reactions include changes in phase, temperature and color. Please be succinct and complete. Do not say “it turned red.” Say rather, “the solution turned red from clear” or “a red solid appeared and the solution remained clear.” Note any temperature change that may occur. If you heat the solution you will not be able to say anything about temperature change during a reaction since the heat supplied will mask any temperature change. However, if you add reactants together and the solution feels hot, make a note of it.

Procedure:

Part I: Copper to Cupric Nitrate (Reaction 1)

1. Weigh approximately 0.500 g Cu wire to three decimal places.

2. Bend the copper wire so it lays flat on the bottom of a 250 mL beaker.

3. In the HOOD add 5 mL concentrated HNO3 using a 10 mL graduated cylinder.

4. Record observations

Part II: Cupric Nitrate to Cupric Hydroxide (Reaction 2)

1. Add 100 mL deionized water to the 250 mL beaker from Part I.

2. Add 30 mL of 3.0 M NaOH solution.

3. Swirl to mix thoroughly.

Video 🡪

4. Record observations.

5. List the reaction type of the reaction equation.

Part III: Cupric Hydroxide to Cupric Oxide (Reaction 3)

1. Add two or three boiling glass beads to the 250 mL beaker from Parts I and II.

2. Set up the hot plate at your desk.

3. Heat on your hot plate while stirring constantly with your stirring rod.

Lab Technique Tip: Stir constantly. Do not let the solution boil vigorously or it may “bump,” that is, spatter out of the beaker violently. Yet you must heat thoroughly until reaction occurs. Look for the end of the reaction by a change in color of the reactants.

Video 🡪

4. When reaction is complete, remove the beaker from the hot plate using hot hands.

5. Begin heating about 250 mL of deionized water to boiling on the hotplate.

6. Allow the reaction solution to cool, about 10 minutes. Do not stir or disturb the solution during this time as you want the solid to settle to the bottom.

7. Record observations and list reaction type.

8. When the solution is cool, decant the liquid away from the solid into your largest beaker or flask.

Lab Technique Tip : Be careful not to decant any of the black “flocculent” solid at the bottom of the beaker. The solid is easily stirred up. Use a steady hand!

9. “Wash” the remaining black CuO product by performing the following steps:

· Add 200 mL of hot distilled water.

· Stir the contents with the glass stirring rod.

· Let the contents settle.

· Decant water into the largest beaker or flask. Again, be careful not to decant any of the black solid.

Part IV: Cupric Oxide to Cupric Sulfate (Reaction 4)

1. Add 15 mL of 6M H2SO4 to the solid CuO in the beaker.

Swirl to mix thoroughly.

2. Observe carefully to monitor any reaction. video

3. Stir the contents from time to time until you see no more evidence of reaction.

4. Record observations and list reaction type.

Part V: Cupric Sulfate to Copper (Reaction 5)

1. Weigh about 2 g of zinc metal and record its appearance.

2. In the HOOD add zinc metal to the solution in the beaker. video

Caution: Do not have any open flames near this reaction, the gas evolved here is flammable.

3. Stir until the mixture becomes colorless. video

4. Monitor the reaction and record observations.

5. List reaction type.

Zn will react with the CuSO4 and will have a side reaction with the H2SO4 present in the solution from the previous step. In the space provided in the Report Sheet, write down both of these reactions. Identify the gaseous, solid and aqueous products that are produced from these two reactions.

6. When there is no more evidence of reaction (no more gas evolution and color is stable), decant liquid into the special waste container.

7. Transfer the contents to a pre-weighed evaporating dish.

8. Wash the solid product with deionized water following these steps:

· Add 10 mL of water and gently stir.

· Let solid settle at bottom.

· Decant water into waste container.

· Repeat a few times.

9. Wash the copper with 5 mL of acetone instead of water by repeating the above steps.

10. Decant acetone into waste container.

11. In HOOD, allow the moist product in the evaporating dish to rest on a slightly warm hot plate until dry.

Caution: You are evaporating acetone here so do not have the heat too high. Remember that acetone is volatile and flammable. No flames anywhere in the lab during this step.

12. Remove glass beads and return them to the cart.

13. Weigh the dry product and evaporating dish and record the mass.

14. Record your observations of your final solid product.

WASTE DISPOSAL: Dispose of the solid product into the waste container for solid copper. Dispose of the liquid from Part III down the sink with excess water. Dispose of the liquid from Part V in the special waste container, NOT down the sink.

Calculations:

% recovery

Mass of copper recovered = mass of evaporating dish and copper – mass of dish

% recovery = x 100%

Sample Problem:

In an experiment, a student starts with 0.580 g of copper. At the end of the experiment, 0.400 g of Cu was recovered. Calculate the percent recovery.

% recovery = x 100%

= 69.0% recovery

We began this lab using copper metal and reacted it with nitric acid to form Cu(NO3)2 . However, we could have started with a Cu(NO3)2 solution instead. To find the starting g of copper from a copper (II) nitrate solution, we will need to use dimensional analysis with the molar mass and subscript conversion factors to determine the mass of copper from the mass of Cu(NO3)2.

Sample Problem:

In an experiment, a student starts with 1.71 g of Cu(NO3)2. At the end of the experiment, 0.43 g of Cu was recovered. What is the starting amount of copper?

To determine the g of Cu we are starting with

Cu = 0.579 g

Reactions of Copper Lab Report Sheet

Name	Date	Conclusion	/ 20
		Report	/ 80
		Total	/ 100

Mass of Cu wire	0.487 g
Mass of evaporating dish	49.362 g
Mass of evaporating dish + recovered Cu	49.815 g
Mass of recovered Cu	g
% Recovery (show calculations)	%

Procedure	Observations	Reaction Type
Part I (Rxn 1)		N/A
Part II (Rxn 2)
Part III (Rxn 3)
Part IV (Rxn 4)
Part V (Rxn 5)

Reactions of Zinc in Part V:

1. Zn (s) + CuSO4 (aq) →

2. Zn (s) + H2SO4 (aq) →

Gas: __________________

Solid: __________________

Aqueous compound: __________________

Conclusion:

Questions:

1. What is the oxidation number of S in each of the following substances?

· H2S

· H2SO4

· HS‒

· SO3 2‒

· SO3

· SO2

· Na2S2O3

· K2S

2. Using the activity series, which of the following reactions will occur? Write yes or no by each reaction to indicate if the reaction will occur or not.

· Au (s) + NaBr (aq) →

· Mg (s) + CuSO4 (aq) →

· KBr (aq) + Zn (s) →

· AgNO3 (aq) + Cu (s) →

· Zn (s) + Al2(SO4)3 (aq) →

3. Indicate the reaction type for each of the following reactions.

Equation	Reaction Type
2C + O2 → 2CO
Cl2 + 2NaBr → 2NaCl + Br2
2N2O5 → 2N2O4 + O2
LiOH + HNO3 → LiNO3 + H2O
2H2O → 2H2 + O2
2Mg + TiCl4 → Ti + 2MgCl2
BaCl2 + (NH4)2CO3 → BaCO3 + 2NH4Cl

4. Write the following balanced equations.

· Solid iron(III) sulfide reacts with gaseous hydrogen chloride.

· Magnesium combines with nitrogen.

· Zinc reacts with silver chloride.