Lab Report: Determination of an Equivalent Mass by Electrolysis 2020/2021 AP Chem PDF

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Stability: The product is stable. Reactive with oxidizing agents, combustible materials, metals, acids. Incompatible with strong acids, selenium, sulfur, wood and other combustibles, nickel nitrate, aluminum, aluminum trichloride, hydrogen, methanol, non-metals, oxidants, sulfur compounds, aniline, ...

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Lab 2 - Determination of an Equivalent Mass by Electrolysis https://media.pearsoncmg.com/bc/bc_0media_chem/chem_sim/html5/Electro/ Electro.php Purpose: The purpose of this lab is to determine the equivalent mass of a metal by electrolysis. MSDS: Nickel (Ni): Stability: The product is stable. Reactive with oxidizing agents, combustible materials, metals, acids. Incompatible with strong acids, selenium, sulfur, wood and other combustibles, nickel nitrate, aluminum, aluminum trichloride, hydrogen, methanol, non-metals, oxidants, sulfur compounds, aniline, hydrogen sulfide, flammable solvents, hydrazine, and metal powders. Toxicology: Hazardous in case of inhalation. Slightly hazardous in case of skin contact (irritant, sensitizer), of ingestion. Nickel dust and fume can irritate eyes. Inhalation of dust or fume may cause respiratory tract irritation with non-productive cough, hoarseness, sore throat, headache, vertigo, weakness, chest pain, followed by delayed effects, including tachypnea, dyspnea, and ARDS Personal protection: Wear appropriate protective eyeglasses, gloves and clothing to prevent skin exposure. http://dept.harpercollege.edu/chemistry/msds1/Nickel%20metal%20shot%20ScienceLab.pdf https://fscimage.fishersci.com/msds/16240.htm Zinc (Zn): Stability: Stable under normal conditions. Zinc metal will react with acids and strong alkalis to generate hydrogen gas. A violent, explosive reaction may occur when powdered zinc is heated with sulphur. Contact with acids and alkalis will generate highly flammable hydrogen gas. Incompatible with strong oxidizing agents. Toxicology: If excessive quantities of zinc oxide fume are inhaled, it can result in the condition called metal fume fever. Mild eye irritation, redness. Personal protection: Wear appropriate protective eyeglasses, gloves and clothing to prevent skin exposure. https://www.teck.com/media/Zinc-Metal-SDS.pdf https://fscimage.fishersci.com/msds/25230.htm Zinc Nitrate (Zn(NO3)2): Stability: Hygroscopic. Avoid dust generation, combustible materials, and moist air. Incompatible with strong reducing agents. Toxicology: Causes eye, skin, digestive tract and respiratory tract irritation. May be harmful if absorbed through the skin, inhaled or swallowed.

Personal Protection: Wear appropriate protective eyeglasses and gloves. Wear a chemical apron and protective clothing to prevent skin exposure. https://betastatic.fishersci.com/content/dam/fishersci/en_US/documents/programs/education/regulatorydocuments/sds/chemicals/chemicals-z/S25901.pdf https://www.mccsd.net/cms/lib/NY02208580/Centricity/Shared/Material%20Safety%20Data %20Sheets%20_MSDS_/MSDS%20Sheets_Silver_Nitrate_Solution_1_0M_625_40.pdf Pre-Lab Assignment: In an electrolysis cell similar to the one employed in this experiment, a student observed that his unknown metal anode lost 0.233 g while a total volume of 94.50 mL of H2 was being produced. The temperature in the laboratory was 250 C and the barometric pressure was 740 mm Hg. At 250 C the vapor pressure of water is 23.8 mm Hg. To find the equivalent mass of this metal, he filled in the blanks below. Fills in the blanks as he did. 1. PH2 = Pbar - VPH2O = 2. VH2 = 3. T = 0C + 273 = 4.

5. 1 mol H2 requires passage of 2 Faradays. 6.

= number of faradays passed

7. Loss of mass of metal anode = 0.233 g 8. Number or grams of metal lost per faraday = 9. The student was told that his metal anode was made of copper. MM Cu = 63.546 g. The charge n on the Cu ion is therefore 1.99 MM = EM * n n n =1.99 Procedure:

1. 2. 3. 4. 5. 6. 7.

For the Cathode select the Zinc metal plate For the Anode, select the Nickel metal plate Record the mass of both starting mass of Zinc and Nickel For the solution select the Zn(NO3)2 solution Go to the ammeter and change the current (amps) from 0 to 5 amps Then go to the timer and slide it all the way to the right for the full 40 minutes Turn on the Ammeter for the reaction to start, you are able to see many of the things on the molecular level if you choose the option, too. 8. Once the full 40 minutes are over record the final mass of both the Zinc and Nickel 9. Repeat these steps until there are seven data trials

Data: Trial 1

Trial 2

Trial 3

Trial 4

Trial 5

Trial 6

Trial 7

Initial Mass 10.00 Zn (g)

10.00

10.00

10.00

10.00

10.00

10.00

Initial Mass 10.00 Ni (g)

10.00

10.00

10.00

10.00

10.00

10.00

Current (A) 5.00

5.00

5.00

5.00

5.00

5.00

5.00

Final Mass Zn (g)

5.93 g

5.90

5.89

5.85

5.97

5.94

5.88

Final Mass Ni (g)

14.07 g

14.10

14.11

14.15

14.03

14.06

14.12

Solution - Zn(NO3)2 (aq) Run Time - 40:00 minutes Calculations: Zn(s) + Ni2+(aq) → Zn2+(aq) + Ni(s) Find Coulombs: -

Use Stoichiometry to find moles of Zn and Ni: Find Faradays:

Find mass of Zn lost: (trial 1) Trial

Mass Zn lost (g)

1

4.07

2

4.10

3

4.11

4

4.15

5

4.03

6

4.06

7

4.12

Calculate Equivalent mass for each trial (trial 1)

Stats:

Trial

Equivalent mass (g)

1

32.7

2

33.0

3

33.1

4

33.4

5

32.4

6

32.6

7

33.1

Average: = 32.9 g Standard Deviation:

= 0.321 g Average Deviation:

= 0.286 g Confidence:

= = 3.06

Confidence Interval: 97%

== 32.9 g ± 0.371 g Conclusion: The average equivalent mass was 32.9 g. Sources of Error: Indeterminate: - Ammeter: 0.01 A - balance : 0.01 g - Stop watch: 0.01 s Propagated: - Stoich calculations

DOT (Theories): *Same as Electrochemical Cells Lab 1: Oxidation and Reduction + Reduction potential chart There are many different types of redox reactions, but the one we usually work with is the one that deals with the transfer of electrons, because that is what produces electricity. Redox reactions consist of a reduction reaction and an oxidation reaction. The way to remember what happens in oxidation and reduction is by using the saying, LEO says GER, which means that oxidation involves the loss of electrons, while reduction involves the gain of electrons. In the reaction between CuO + Mg → Cu + MgO, the oxidation reaction has electrons in its products, while the reduction reaction has electrons in its reactants. The reducing agent is the reactant getting oxidized. The oxidizing agent is the reactant getting reduced. This relates to electrochemistry through the reduction potential charts. As shown in the reaction

E0= ERED + EOX, the cell potential of a reaction can be determined

using the reduction potential chart. Essentially, the reduction or oxidation potential of a certain reaction indicates how likely it is that the reaction will reduce or oxidize. If the reaction has a strong reduction potential, it will have a low oxidation potential. From a reduction potential chart, the oxidation potential can be found because the oxidation potential is opposite in sign and of same magnitude of the reduction potential 2: Voltaic and Electrolytic Cells There are two types of cells that can provide electricity through the transfer of electrons, one is electrolytic cells and the other is voltaic cells. The main difference between the cells is that voltaic cells are spontaneous and electrolytic cells are non-spontaneous. Therefore, electrolytic cells require an outside source of power such as a battery. The anode is where oxidation occurs. The cathode will always be the reduction half in both voltaic and electrolytic cells. In a voltaic cell electrons flow from the anode to the cathode. As Zinc oxidizes, it is producing electrons which are transferred to the reduction reaction. The Copper 2+ is able to become Copper (s) as it is using the electrons that came from the oxidation reaction. Finally, the salt bridge prevents the cell from short-circuiting. There is a charge imbalance that is created as electrons are transferred

from the anode to the cathode. As the anode loses electrons, the negative Cl- ions are used to replace them and as the cathode gains electrons, K+ ions flow to the cathode solution. It's important to note that voltaic cells can reach a voltage of zero after time if all reactants and ions in the salt bridge are consumed, which is why the voltmeter/lightbulb is there to indicate the state of the cell. 3: The Nernst Equation The Nernst equation is E Cell= Eº-(RT/nF)lnQ. ECELL is the cell’s new potential after it has been adjusted due to its temperature and Q value. Eº is the cell potential at standard temperature and concentration: 298 K and 1 M concentrations. R is the gas constant. T is the new temperature at which ECELL is measured. n is the number of moles of electrons transferred within the reaction, and it can be used with Faraday’s constant, which is 96,500 C/ 1 mole e-. Finally Q is the new equilibrium value after the temperature has been changed. When Q = K, which is when the reaction is at equilibrium, there is no net transfer of electrons. If there is no net transfer of electrons, the voltage and cell potential will be 0, because electricity and voltage are created due to the movement of electrons. It is seen in the equation that when Q is less than 1, the cell voltage is greater than it would be at standard equations because the lnQ becomes negative. The Q value is only less than one when the reactants have a higher concentration than the products. As the reaction progresses, there will be a point where the reactant and product concentrations are equal. At this point Q = 1, and this is when the standard cell potential is equal to the new temperature potential. However, as more products are formed, Q becomes more than one, causing ECELL to be lower than Eº. DOT(Apps): *Same as Electrochemical Cells Lab Biology/Medicine: Permanent Hair Removal Electrolysis can be used for removing unwanted hair. Using a fine needle as a probe, measured electric currents are applied to the hair follicles through the needle. This process destroys the roots of the hair and hinders any further growth. The oldest method of electrolysis for hair removal is galvanic electrolysis, which uses the electrical current to drive a chemical reaction that destroys the follicle. Much like in a battery, galvanic electrolysis is initiated by a direct electrical current (DC). When the charge is applied, it reacts with the salinity or solution of salt water at the base of the hair follicle, producing sodium hydroxide, or lye, hydrogen gas, and chlorine gas. Lye is a highly corrosive agent that will dissolve the base of the hair follicle, which is called the dermal papilla. After several treatments, the permanent damage to the follicle’s surrounding tissue prevents any regrowth of hair. The actual current is delivered in a needle probe directly connected to the electrolysis machine, where a medical professional can control the amperes of current passed into the dermal papilla. The device is generally held in place for about two minutes after insertion. Industrial: Electroplating Electroplating or electrodeposition is a process that results in a thin layer of metal being

deposited on the surface of a substrate, which can be other metals and alloys like aluminum, copper, magnesium, and steel or plastics, ceramics, and even glass. Electroplating is used to change the physical properties of the substrate, and can be used to give objects wear resistance, corrosion protection, or aesthetic appeal. The four components of the system are the anode, the cathode, the solution, and the power source. The anode (positively charged) in the circuit is the metal that will form the plating, while the cathode (negatively charged) is the substrate that needs to be plated. The electrolytic solution is where the reaction takes place. This solution contains one or more metal salt. Electricity is introduced to the system using a power source that applies a direct current (DC) to the anode. The metal then oxidizes, allowing metal atoms to dissolve in the solution as positive ions. The current causes the metal ions to move to the substrate and deposit in a thin layer. For example, this process is used to plate gold on metal jewelry. The power is supplied to the gold, which dissolved in the solution and adheres to the base metal. Minority Scientist: Lynden Archer Lynden Archer, a African American chemical engineer and professor of chemical engineering at Cornell University worked with a doctoral student Wajdi Al Sadat to generate strategies to reduce carbon emissions and mitigate climate change. In 2016, they released a paper revealing their idea for the development of an oxygen-assisted aluminum/carbon dioxide power cell that uses electrochemistry to sequester carbon dioxide and produce electricity. The electrochemical cell they proposed in their paper would use aluminum as the anode and mixed streams of carbon dioxide and oxygen as ingredients of the cathode. The cell first reduces oxygen at the cathode to form a superoxide. This superoxide reacts with the carbon dioxide and sequesters it in the form of aluminum oxalate (Al2(C2O4)3). This electrochemical cell offers an important strategy that may be used for the net reduction of carbon emissions....