CHEM 1010H Lecture Notes - Lecture 4: Potassium Iodide, Specific Volume, Hydrogen Peroxide

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limesardine235

28 Jul 2016

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H2o2 (in part 1) of the experiment? (give a detailed explanation of any observations that you made, i. e. , what made the colour change, what reactions happened?) Tube #1 the first tube was composed of hydrogen peroxide and a solution of ki. The reaction occurs when the ions reacts with hydrogen and peroxide ions to form and . The solution went from clear with the ions to yellow-brown when the is formed. Tube #2 in the second tube, starch was added. This caused another reaction between the and the starch forming a purple colour, which indicates that the first reaction between the hydrogen peroxide and ki did indeed take place. Tube #3 in the third tube, sodium thiosulfate was added. This addition caused the that was present in the solution to react with the sodium thiosulfate, which formed ions and also this solution then goes from yellow to clear as the ions are paired up.

Related Questions

Please check my work. I am have to bring my grade up so I need to make sure I get these right this week Here are my notes and answers from lab this week please let me know if I missed any.

NOTES:

Experiment 1: The Effect of Temperature on Catalase Activity

Test tube #1(10ÃÂ°C)

Add 5 mL of 3% hydrogen peroxide

Add 5 mL of water

Add 1 mL of catalase

Observe bubbles: No bubbles observed (or very, very little)

Color changed to red

Test Tube #2 (21.5ÃÂ°C)

Add 5 mL of 3% hydrogen peroxide

Add 5 mL of water

Add 1 mL of catalase

Observe bubbles: Bubbles appeared quickly and constantly for the first 10 seconds then stopped

Color changed to red

Test Tube #3 (40ÃÂ°C)

Add 5 mL of 3% hydrogen peroxide

Add 5 mL of water

Add 1 mL of catalase

Observe bubbles:Bubbles appeared slowly and Sporadically for about 10 seconds then stopped.

Color changed to red

Test Tube #4(60ÃÂ°C)

Add 5 mL of 3% hydrogen peroxide

Add 5 mL of water

Add 1 mL of catalase

Observe bubbles: Bubbles appeared instantly and continued sporadically continued for 10 seconds

color changed to red

Test Tube #5 (80ÃÂ°C)

Add 5 mL of 3% hydrogen peroxide

Add 5 mL of water

Add 1 mL of catalase

Observe bubbles:Bubbles appeared instantly, and sporadically continued for about 10 seconds then stopped.

Color of solution changed to red.

Experiment 2: The Effect of Substrate Concentration on Catalase Activity

Test Tube #1

Add 8mL Water

Add 2mL 3% Hydrogen Peroxide (mL)

Add 0.1 mL of catalase

Time for bubbles to stop forming: .38 seconds

Test Tube #2

Add 5mL Water

Add 5mL 3% Hydrogen Peroxide (mL)

Add 0.1 mL of catalase

Time for bubbles to stop forming: 32 seconds

Test Tube #3

Add 2mL Water

Add 8mL 3% Hydrogen Peroxide (mL)

Add 0.1 mL of catalase

Time for bubbles to stop forming: 28 seconds

Test Tube #4

Add 0mL Water

Add 10mL 3% Hydrogen Peroxide (mL)

Add 0.1 mL of catalase

Time for bubbles to stop forming: No bubbles

Experiment 3: The Effect of pH on Catalase Activity

Test Tube #1 (21.5ÃÂ°C)

Add 5 mL of 3% hydrogen peroxide

Add 5 mL of pH 2 buffer

Add 1 mL of Catalase Solution

Observation: No bubbles

Test Tube #2 (40ÃÂ°C)

Add 5 mL of 3% hydrogen peroxide

Add 5 mL of pH 6 buffer

Add 1 mL of Catalase Solution

Observation: bubbles appear immediately

Test Tube #3 (60ÃÂ°C)

Add 5 mL of 3% hydrogen peroxide

Add 10mL of pH 10 buffer

Add 1 mL of Catalase Solution

Observation: no bubbles.

Experiment 1: The Effect of Temperature on Catalase Activity

Lab Results

At which temperatures did catalase function somewhat, but not optimally?

40 degrees the bubbles appeared slowly and continued sporadically for about 10 seconds before stopping. At 60 & 80 degrees the bubbles appeared immediately but were sporadic as well.

Data Analysis

Why did catalase fail to function at 80 Â°C?

Because the Enzyme catalase denatures

Experiment 2: The Effect of Substrate Concentration on Catalase Activity

Lab Results

Fill in the table below with your results from the substrate concentration experiment.

Substrate Concentration Results
Test Tube	Bubbles Formation (min)
1	00:38 seconds
2	00:32 seconds
3	00:28 seconds
4	No bubbles.

Data Analysis

Before the catalase concentration was saturated with hydrogen peroxide, why did the enzyme function vary with substrate concentration?

The enzymes had varied results before the catalyst concentration was changed due to the differences in temperature. In experiment one all measurements were the same, the variable was the temperature. In experiment two, the concentrations of each material were the variable along with the temperature.

Experiment 3: The Effect of pH on Catalase Activity

Lab Results

What was the pH value at which catalase functioned the best?

pH 6 buffer

Data Analysis

Why did catalase only function in a limited range of pH values?

Conclusions

What are the enzyme, substrate, and product in these experiments?

The enzyme is Catalase

The Substrate is Hydrogen peroxide

The product was the bubbles.

What role does catalase play in the mammalian liver, or any other cell it is found in?

Catalase is an enzyme in the liver that breaks down harmful hydrogen peroxide into oxygen and water. When this reaction occurs, oxygen gas bubbles escape and create foam.

Reference:

https://www.scientificamerican.com/article/bring-science-home-liver-helping-enzymes/

Procedure Reaction 1: Dissolving the Copper 1. Obtain a clean, dry, glass centrifuge tube. 2. Place a piece of copper wire in a weighing paper, determine the mass of the wire and place it in the centrifuge tube. The copper wire should weigh less than 0.0200 grams. 3. In a fume hood, add seven drops of concentrated nitric acid to the reaction tube so that the copper metal dissolves completely. Describe your observations in the lab report. (Caution, Concentrated nitric acid and nitrogen dioxide are very corrosive. Either will turn your skin yellow on contact. Do not leave any spills on the lab bench or in the fume hood.) 4. When the copper has dissolved, add seven drops of distilled water to the tube. Reaction 2: Preparation of Copper(II) Hydroxide 1. Add 15 drops of 3.0 M aqueous sodium hydroxide to the tube. Make sure that the reactants are well mixed. Shake the tube carefully or gently flick the bottom of the tube with your finger. Remember that the contents of the tube may still be corrosive. 2. Add a second 15 drops of NaOH(aq), mix well, and record your observations. If you have two layers at this point it means that you have not mixed the solution well enough. 3. Centrifuge the reaction mixture. 4. The liquid at the top of the centrifuged mixture is called the supernatant while the solid is called a precipitate. Before separating the supernatant from the precipitate it is necessary to ensure that all of the copper(II) hydroxide has been precipitated. The supernatant should be clear and colorless indicating the absence of any Cu+2 ions in the solution. It should also be basic due to an excess of OH- ions. Using a clean glass stirring rod, transfer a drop of the supernatant onto a piece of red litmus paper. If the litmus paper turns blue then the solution is basic and enough NaOH has been added. If the paper does not turn blue, add more NaOH, mix well, recentrifuge, and repeat the litmus paper test until the paper does turn blue. 5. An efficient separation of supernatants and precipitates is key to obtaining a good final yield of copper. The supernatant liquid can be separated from the precipitate by expelling the air from the bulb of a Pasteur pipet, inserting the tip of the pipet into the supernatant, then gently sucking the supernatant into the pipet. If you expel air or liquid into the precipitate with the pipet, you will stir up the precipitate and will have to repeat the centrifugation step. Remove as much liquid as possible and discard it in the waste container provided on the instructorâs cart. It is better to leave a small amount of supernatant liquid than to remove some of the copper(II) hydroxide precipitate. Reaction 3: Formation of Copper(II) Oxide 1. Set up a hot water bath by placing a beaker of water on a hotplate, placing an iron ring around the beaker, and heating the water to boiling. 2. Place the centrifuge tube containing the copper(II) hydroxide into the boiling water. Carefully hold the tube with a test tube clamp so that it doesnât get water into it. Record your observations. Reaction 4: Formation of Copper(II) Sulfate 1. Add 20 drops of 3.0 M H2SO4 to the solid in the centrifuge tube. Stir carefully to ensure that the copper(II) oxide dissolves completely. Complete dissolution of the mixture will require thorough mixing and possibly heating of the solution. 2. Obtain the mass of a small, clean, glass test tube as accurately as possible. 3. Transfer the liquid from the centrifuge tube into the test tube. Rinse the centrifuge carefully with 1.0 mL of distilled water and transfer the rinse into the test tube containing your sample. 4. Record your observations on the data sheet. Reaction 5: Formation of Copper Metal 1. Add a small quantity of zinc powder to the sample solution. Continue adding zinc in small quantities until the solution loses the blue copper(II) color. Any excess zinc added will need to be removed so donât add it too quickly or in large quantities. When the solution has turned colorless, add several drops of 3.0 M H2SO4 to the tube to dissolve any left over zinc. You can tell that the zinc has dissolved when addition of sulfuric acid does not generate bubbles. 2. Allow the copper metal to sink to the bottom of the tube and carefully remove the supernatant liquid using a Pasteur pipet. 3. Wash the red-brown copper metal in the tube with 1.0 mL of water. Allow the copper metal to settle to the bottom and remove the excess water. Repeat this rinsing process two more times. 4. Describe your observations on the data sheet. Drying the copper metal 1. After removing as much of the third rinse water as possible you are ready to dry the metal. This must be done carefully in a cool Bunsen Burner flame. If the tube is heated too quickly there is a risk of ejecting the contents of the tube as the water boils. Also, if the flame is too hot you may convert the copper metal back into black copper(II) oxide. The objective is to drive the water from the tube as steam. Make sure that as water condenses on the walls of the tube that you continue to heat until all of the water if gone from the tube. 2. Once all of the water is removed from the tube, cool the tube and its contents then determine the mass of copper by weighing the tube and subtracting the tube + copper weight from the weight of the empty tube (Reaction 4 step 2). If the mass of copper is higher than the original mass of the copper wire it either contains water or zinc or has been converted to copper(II) oxide. Excess water can be removed by reheating the tube and reweighing to constant mass. Excess zinc requires addition of sulfuric acid followed by re-rinsing with water and re-drying. Chemistry 1215 Experiment 9 Lab Report Name ______________________________ Data Sheet Mass of copper wire _______________ Mass of clean, dry test tube _______________ Mass of test tube plus copper _______________ Mass of final copper sample _______________ Percent recovery of copper. Show all calculations. Observations 1. Describe your observations for Reaction 1 including colors, gases formed, etc. 2. Describe your observations for Reaction 2 including colors, gases formed, etc. 3. Describe your observations for Reaction 3 including colors, gases formed, etc. Estimate the temperature of the decomposition of Copper(II) hydroxide. 4. Describe your observations for Reaction 4 including colors, gases formed, etc. 5. Describe your observations for Reaction 5 including colors, gases formed, etc. Write a brief discussion of your results including a statement of the final percent recovery of copper and a discussion of reasons why the recovery differs from 100%. Chemistry 1215, Experiment #9; Copper and its compounds, Pre-lab Name ____________________________________ 1. Write a balanced chemical equation including phase labels for the reaction between aqueous copper (II) nitrate and aqueous sodium hydroxide. 2. Nitrogen monoxide (NO) and nitrogen dioxide (NO2) are toxic, corrosive gases that significantly lower blood pressure when inhaled. How are these gases produced in todayâs experiment? What should you do to protect yourself against their toxicity? 3. Iron reacts with oxygen from the atmosphere to produce iron (III) oxide, also known as rust (Fe2O3). What chemical species is oxidized in this reaction? What is the reducing agent? Jaffrey Zagnut couldnât find any nitric acid so he tried to dissolve his copper sample in hydrochloric acid instead. Unfortunately his copper wouldnât dissolve in HCl. Why will copper dissolve in nitric acid but not in hydrochloric acid (after all, HCl is a stronger acid than HNO3). Chemistry 1215, Experiment #9; Copper and its compounds, Post-lab Name ____________________________________ 1. Copper (II) hydroxide is converted into copper (II) oxide by heating the test tube containing Cu(OH)2 in a hot water bath. Is it necessary to use distilled water in this water bath? Why or why not? 2. Copper metal doesnât ârustâ in the presence of oxygen at room temperature. However, it will react with O2 at elevated temperatures. Write a balanced chemical equation describing the formation of copper (II) oxide when copper metal is heated in air. 3. When zinc is dissolved in sulfuric acid a gas is produced. What is the chemical identity of this gas? How is it produced? 4. Jaffrey Zagnut started with a 0.032 g sample of copper which he took through the series of reactions described in this experiment. At the end of the experiment he obtained 0.038 g of a black product. What was his percent yield? What is the most likely source of the error in his experiment? (Hint: consider question 2 above)

CHEM 1010H Lecture Notes - Lecture 4: Potassium Iodide, Specific Volume, Hydrogen Peroxide

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