Experiment 20 balanced chemical equations

Unit 8

Purpose: ​The purpose of this lab is to observe and differentiate between chemical

reactions and to learn how to write balanced chemical equations for them.

Procedure:

Experiment 1:

1. Make sure you put on your gloves and goggles before you start.

2. First, take a test tube, the silver nitrate, the copper pieces, and the plastic

tweezers and set them aside.

3. Observe and record the initial appearance of the silver nitrate and the copper.

4. Then, using the plastic tweezers, add two pieces of copper into the test tube.

5. Next, add all the silver nitrate into the test tube and throw out the empty bottle.

6. Observe and record the reaction for up to a minute and then describe the

appearance of all solid, liquid, and gas in the test tube.

7. Let the reactions go on for another 30 minutes, then observe and record the

appearance of the all the solid, liquid, and gas.

8. Write the balanced chemical equation for the redox reaction on a sheet of paper,

including the oxidation numbers and total charge. Take a photo and upload it.

9. Figure out which one of the elements has been reduced and which one is the

spectator ion. Record your observations.

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10. Figure out which element was the oxidizing agent and which was the reducing

agent in the experiment. Record your observations.

11. Clean up the materials used properly.

Experiment 2:

1. First, take the 24 well plate and place it on top of a paper with labels for the well

plate. Label wells A1, A2, B1, B2, C1, and C2.

2. Next, put a piece of copper in both well plate A1 and well plate A2.

3. Then, take the pipet with the lead (II) nitrate and cut off the tip of the pipette. Add

15 drops of the lead (II) nitrate to well A1.

4. Observe and record the chemical reaction in well A1 after a minute.

5. Let the reaction in well A1 continue for 30 more minutes.

6. Meanwhile, cut off the tip of the pipette containing the zinc nitrate. Add 15 drops

of zinc nitrate to well A2.

7. Observe and record the chemical reaction in well A2 after a minute.

8. Take the plastic tweezers to grab two pieces of lead and place it on a piece of

paper towel.

9. Then, take a nail filer and scrape the top of the lead to take off the rust.

10. Put the two pieces of lead, one in each, wells B1 and B2.

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11. Dispose of the paper towel with the lead leftovers on it. Also, throw out the nail

filer.

12. Take your gloves off inside out and throw them away. Wash your hands with

soap and dry them with paper towels, throwing the paper towels out afterwards.

13. Put on a new pair of gloves.

14. Next, take the pipet with the copper (II) sulfate and cut off the tip. Add 15 drops

of the copper (II) sulfate to well B1. Observe and record the reaction after a

minute.

15. Then, add 15 drops of Zn(NO3)2 to well B2. Observe and record the reaction

after a minute.

16. Put one piece of mossy zinc in well C1 and one piece in well C2.

17. Add 15 drops of CuSO4 to well C1. Observe and record the reaction after a

minute.

18. Add 15 drops of Pb(NO)2 to well C2. Observe and record the reaction after a

minute.

19. After 30 minutes, observe and re-record all the reactions so far.

20. Fill in the data tables with the all observations.

21. Write balanced chemical equations for all the reactions that occurred, including

the oxidation numbers and the total charge. Take a picture and upload it.

22. Clean up the materials used properly.

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Observation & Data:

Data Table 1: Redox Reaction of Copper and Silver Nitrate

Initial

Observations

before Beginning

The copper pieces are a bronzish color while the silver nitrate is

clear.

Observations

First, the copper turned white with bubbles and then black. Also,

it kind of fluffed up (like a pill when it dissolves). The liquid is

clear.

Observations

after 30 min

The pieces combined and turned crystallized. It turned a

combination of white, brown, and black in color. The liquid also

turned into a slight light blue green color.

Element that is

Oxidized

Copper

Element that is

Reduced

Silver

Spectator Ion None

Oxidizing Agent Copper

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Reducing Agent Silver

Data Table 2: Redox Reactions of Copper, Lead, and Zinc

Solid Metal

Well ID

Solution

Immediate

Observation

30 Minute

Observation

Cu

A1

Pb(NO​3​)​2

The liquid is clear while

the copper is bronze in

color.

There was no

change.

Cu

A2

Zn(NO​3​)​2

The liquid is clear while

the copper is bronze in

color.

There was no

change.

Pb

B1

CuSO​4

There are a few

bubbles that form

around the lead, which

turns bronze in color.

The lead starts to

rust.

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Pb

B2

Zn(NO​3​)​2

The lead is silver in

color.

There was no

change.

Zn

C1

CuSO​4

The zinc turned reddish

from the top.

The zinc was black

with a little bit of red

on the top.

Zn

C2

Pb(NO​3​)​2

The zinc turns black.

The zinc becomes

dark grey from the

top.

Data Table 3: Potential Redox Reactions and Chemical Equations

Metal and Metallic Solution Reaction Occurred?

Cu + Pb(NO​3​)​2 None

Cu + Zn(NO​3​)​2 None

Pb + CuSO​4 Pb2 (aq) + Cu(SO4)2- (aq) → PbSO4 (s)

Pb + Zn(NO​3​)​2 None

Zn + CuSO​4 Zn + CuSO4 → Cu + ZnSO4

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Zn + Pb(NO​3​)​2 Zn + Pb(NO3)2 → Pb + Zn(NO3)2

Photo Results:

Photo 1: Chemical Equation for Redox of Copper and Silver Nitrate

Photo 2: Chemical Equations and Redox Numbers for Reactions

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Questions:

Exercise 1:

1. Define oxidation, reduction, and oxidation number. Describe how oxidation and

reduction affect the oxidation number of an element.

○ Oxidation is the process of being oxidized. Reduction is when a chemical,

during a reaction, gains electrons. The oxidation number is the number of

electrons that is either gained or lost by the element. The oxidation and

reduction affect the oxidation number of an element is that when an

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element is oxidized or reduced, the reduction number will either increase

or decrease.

2. Define oxidizing agent, reducing agent, and spectator ion.

○ An oxidizing agent gains electrons and then reduces in the chemical

reaction that is going on. The reducing agent is when oxidation occurs

when an element loses electrons during a reaction. A spectator ion is both

a reactant and a product in a chemical reaction.

3. In the reaction of copper and silver nitrate, a new substance appeared in the test

tube. Describe the physical appearance of the substance and identify its

chemical formula.

○ The new substance that appeared in the test tube during the reaction of

copper and silver nitrate was a silverish metallic looking substance. The

chemical formula for the substance would be Cu + 2AgNO3 = Cu(NO3)2 +

2 Ag. (This is if we assume the substance is silver or Ag.)

4. Given an activity series in which the most active metals are at the top of the list

and the least active metals are at the bottom of the list, would copper be listed

above silver or would silver be listed above copper? Support your answer with

data from Data Table 1.

○ Copper would be listed above silver. The copper reacted more than the

silver during the experiment. That is why during the experiment the copper

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was the element that was oxidized was also the oxidizing agent, whereas,

the silver was the element that was reduced and was the reducing agent.

5. Solid copper sulfide and silver nitrate react to form copper (II) nitrate and solid

silver sulfide. Write a balanced chemical equation that describes the reaction.

Identify the oxidation number of each element in the reaction. (You do not need

to include the total contribution of charge.) Is this reaction a redox reaction or a

non-redox reaction? Explain your answer.

○ The chemical equation that describes the reaction is: CuS (s) + 2AgNO3

(aq) --> 2Ag2S (s) + Cu(NO3)2 (aq). The oxidation number of each

element, in order, are: (+2 -2), (+1 +5 -2), (+1 -2), and (+2 +5 -2). This is a

non-redox reaction.

Exercise 2:

1. List each of the metals tested in Exercise 2. Indicate the oxidation number when

each element is pure and the oxidation number when each element is in a

compound.

○ Metals: Cu, Pb, and Zn. Oxidation # - Pure: 0, 0, and 0. Oxidation # -

Compound: +2, +2, and +2.

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2. Which of the metals in Exercise 2 was the strongest oxidizing agent? Was there

an instance when this metal also acted as a reducing agent? Explain your

answer using data from Data Table 3.

○ The metal that was the strongest oxidizing agent was copper. I don't think

copper is the reducing agent because it is more so the oxidizing agent

during the reactions.

3. Which of the metals in Exercise 2 was the strongest reducing agent? Was there

an instance when this metal also acted as an oxidizing agent? Explain your

answer using data from Data Table 3.

○ The strongest reducing agent was zinc. There weren't any instances when

the metal also acted as an oxidizing agent. The oxidization was done

more by the copper.

4. How does ease of oxidation correlate with activity? Do highly active metals tend

to donate electrons or accept electrons from other metals?

○ The ease of oxidation correlates with the activity because the more active,

the easier it is to oxidize. The highly active metals tend to donate electrons

to other metals.

5. Create an activity series for copper, lead, and zinc. Place the most active metal

at the top of the list.

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○ The most active metal at the top of the list would be Zn, the second would

be Pb, and the third Cu.

Conclusion: ​Overall, the experiment showed the difference in chemical reactions

depending on the activity level of the metal being used. Using elements like silver

nitrate, copper, zinc, lead, and more, one can see that the reaction and the reaction

time differs. On one hand, there wasn’t much of a difference when the copper reacted

with the lead (II) nitrate vs. when it reacted with zinc nitrate. Both times there was no

change. Whereas, when the lead reacted with the copper (II) sulfate vs. when it reacted

with the zinc nitrate, there was a difference. The lead reacted more with the copper (II)

sulfate then it did with the zinc nitrate. Like so, it was quite interesting to see the

difference in the reactions depending on which combination of elements and chemicals

are used.