CHEM 1000H Lecture Notes - Lecture 1: Redox, Sulfuric Acid, Graduated Cylinder

36 views4 pages

blushelephant621

15 Oct 2018

School

Department

Course

Professor

For unlimited access to Class Notes, a Class+ subscription is required.

Document Summary

Mass of empty container (for weighing the copper): 29. 1549g. Mass of empty container (for weighing zinc): 32. 9934. Mass of watch glass + filter paper: 33. 0868. Mass of watch glass + filter paper + final recovered cu product: 33. 5971: fill in the table for each of the reaction steps. When nho3 was added to the copper, a instant change of color to clear green. As the reaction continued, a brown gas (nitrogen gas) formed between. A the solution and watch-glass covering the top of the beaker, heat was also given off meaning the reaction was exothermic. When the contents of the beaker were transferred into another beaker with de-ionized water, the color changed to a clear light blue. When the naoh was added it turned to a dark cloudy blue. B given off during this process meaning the reaction was also exothermic. While heating the beaker, the substance gradually became darker till it was black.

Related Questions

Calculations First Trial UPDATED

Theoretical yield (CaCO3):

Actual yield (CaCO3):

Percent yield:

Moles of Ca present in original solution, based on actual yield:

Mass of CaCl2 present in original solution, based on actual yield:

Can someone please help me with these three easy questions please? Thank you! SHOW ALL WORK!!

THIS IS MY DATA FROM MY LAB EXPERIMENT. I JUST NEED FOR YOU TO FIND THE ANSWERS TO THE ABOVE QUESTIONS WITH WORK SHOWN!

Table 1: Data and Observations
	Mass
CaCl₂ :	ORGINAL MASS: 2.0g AFTER 24 HOURS 5.8g
K₂CO₃ :	2.5g
Filter Paper	2.1 g
Watch Glass	33.6g
Precipitate	3.3g

Procedure

Put on your safety glasses and gloves (provided in your safety box).

Turn on the scale by pressing the button labeled "0/T". If your scale does not turn on, you may have to remove the battery cover and remove a small strip of plastic from the battery housing. Once the scale is on, press the "0/T" button a second time to zero the scale. Make sure that the units are in grams (g). If not, press the M button until the units displayed are in grams.

Place a weigh boat on the scale and record the mass in Table 2. Zero the mass of the weigh boat by pressing the "0/T" button. Your scale should now read 0 g.

Add 2.0 g of CaCl₂ to the weigh boat. Record the mass in Table 2. Set this sample aside, and let it sit exposed to the air (but otherwise undisturbed) for 24 hours. Complete Steps 3 - 23 while you wait.

Place a 250 mL beaker on the scale and zero it.

Add 2.0 g of CaCl₂ to the beaker. Record the exact mass of the powder in Table 1.

Remove the beaker from the scale. Use a 100 mL graduated cylinder to measure and pour 50 mL of distilled water into the beaker and mix with the stir rod until all the CaCl₂ has dissolved.
Note: This is an exothermic process, so the beaker may become warm.

Place a 50 mL beaker on the scale and zero the scale.

Add 2.5 g of K₂CO₃ to the 50 mL beaker. Record the exact mass of the powder in Table 1.

Remove the beaker from the scale. Use the 100 mL graduated cylinder to measure and pour 25 mL of distilled water into the 50 mL beaker. Mix with the stir rod until all the K₂CO₃ has dissolved.

Rinse the stir rod with water.

Add all of the K₂CO₃ solution to the beaker containing the CaCl₂ solution. It is important that all of the K₂CO₃ is added to the beaker. To ensure this, rinse the 50 mL beaker with up to 5 mL distilled water, and pour the rinse in the CaCl₂ solution.

Using the stopwatch to keep time, stir the solution with the stir rod for four minutes. Then, allow it to sit for 15 minutes. This will allow sufficient time for the chemical reaction to occur.

Rinse the stir rod with water.

Place a piece of filter paper on the scale and record the mass in Table 1.

Place a watch glass on the scale and record the mass in Table 1.

Fold the filter paper in half and in half again so that it resembles a triangle with one arched side.

Pull apart one fold of the filter paper so that three sides of the filter paper remain together, with one side making up the other half of the funnel shape (Figure 5).

Hold the funnel over a sink or any sized container. Place the paper into the funnel and use a pipette to drip 5 mL of distilled water around the edges of the filter paper. This will prevent the filter paper from rising up out of the funnel.

Rest the funnel on top of the Erlenmeyer flask.

After 15 minutes has passed, swirl the beaker and slowly filter the solution (that you created in Step 9) from the 250 mL beaker through the filter paper. Additional distilled water may also be used to transfer any remaining solid into the filtration apparatus.

After all the solution has been filtered, use the pipette to rinse the filter paper with approximately 5 mL of isopropyl alcohol to aid the drying process. Allow the isopropyl alcohol to completely drip through the filter before removing filter paper from the funnel.

Carefully remove the filter paper. Unfold and place it precipitate-side up onto the pre-weighed watch glass. Be sure not to lose any precipitate during this transfer.

Allow the precipitate to dry, undisturbed, for at least 24 hours. Determine the mass of the product recovered by re-weighing the system and subtracting the weight of the filter paper and watch glass. Record your data in Table 1.

Re-weigh the sample of CaCl₂ that was allowed to sit exposed for 24 hours. Subtract the mass of the weigh boat and record the mass and your observations in Table 2.

TABLE 2 IS NOT IMPORTANT IN SOLVING THE QUESTION AS IT JUST ASKS FOR MY OBERVATION OF CaCl₂ AFTER 24 HOURS. ALSO TO FIND THE ACTUAL YIELD, YOU WOULD HAVE TO FIND FIRST THE PERCENT YIELD AND THEORTICAL YIELD.

Questions are in the data analysis and this is my data

3. After setting up we measured the crucible to weigh 31.353 grams

4. next we measure the mass of the copper chloride hydrate mass using the weigh paper. It came out with a mass of 1.045grams.

Next we put the copper chloride in the crucible

After that we measured them all together and it weighed 32.4 grams.

5. We put the crucible on the clay triangle and did not tilt the lid be cause lab instructor told us not to

6. Next we sparked the flame to the Bunsen burner

7. Now with the Bunsen burner lit we are ready to observe. As the substance started to heat it up it started slowly to turn greenish and then was slowly turning brown. It is turning brown from the outside walls of the substance to the inside. After all the heating it slowly turned a little light brown, but brown.

8. Once heating is completed, turn off the equipment and allow the sample to cool.

a. Turn off the Bunsen burner.

b. Use a pair of crucible tongs to place the crucible on a wire mesh screen on the

bench.

c. With the tongs, move the lid so that it covers the crucible bottom completely.

Allow the sample to cool for about ten minutes.

9. Remove the crucible cover and carefully inspect the sample. If any of the sample has

maintained its initial appearance, reheat the sample until all of it has reacted.

10. After we allowed the sample to cool we then measured it and it had a mass of 32.222 g

11. next we are adding the deionized water to the cooled dried sample. We rinsed out the crucible and added it to the beaker with around a total of 16mL of DI water. Once initially added it was green on the bottom with precipitate was left on the bottom and blue on the top. After we stirred it now it is light blue and clear. It is just really light blue now and clear.

12. we obtained a piece of aluminum wire we coiled it and stirred it. Its turning from blue to greyish color and its fizzing and it getting warmer. After a little bit there is now copper on the bottom of the beaker. They are redish color and the solution on top is also a redish color.

13. we obtained 10mL of 6 M HCl solution. Next we dropped them in and the solution is fizzing again.

14. we put the filter paper on the filter paper and are now filtering the substance.

15. mass of dry watch glass 39.025 grams

16. 39.278 grams and second time was 39.274

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 1000H Lecture Notes - Lecture 1: Redox, Sulfuric Acid, Graduated Cylinder

Document Summary

Get access

Related textbook solutions

Chemistry: Structure and Properties

Basic Chemistry

Principles of Chemistry Molecular Approach

Chemistry: Structure and Properties

Principles of Chemistry Molecular Approach

Chemistry: A Molecular Approach

Chemistry: A Molecular Approach

Principles of Chemistry: A Molecular Approach

Chemistry: The Central Science

Related Documents

CHEM101 Study Guide - Final Guide: Copper(Ii) Sulfate, Bunsen Burner, Incandescent Light Bulb

CHEM120L Study Guide - Final Guide: Weak Base, Perchlorate, Rydberg Formula

CHEM120L Study Guide - Final Guide: Zinc Chloride, Sulfuric Acid, Phenol

Related Questions