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Test 1 for OH- and H+ ions

Use the graduated cylinder to measure and pour 10 mL of tap water into a test tube.
Add about 10 drops of 4.5% acetic acid to the water.
Test the resulting solution with blue litmus paper to confirm the presence of H+ ions. Record your observations in Table 2.
Discard your solution in the sink with water (this is a very dilute solution of vinegar). Rinse your test tube three times with water so that it will be clean for the next test.
Test 2 for OH- and H+

In a clean test tube add 10 mL of tap water.
Add 1/2 tsp. of sodium bicarbonate (baking soda) to the water and stir gently.
Test the resulting solution with blue litmus paper to confirm the presence of OH- ions. Record your observations in Table 3.
Discard your solution in the sink with water (this is a very dilute solution of baking soda)

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Keith Leannon
Keith LeannonLv2
28 Sep 2019

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Related questions

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 instructor’s 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 doesn’t 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 don’t 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 today’s 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 couldn’t find any nitric acid so he tried to dissolve his copper sample in hydrochloric acid instead. Unfortunately his copper wouldn’t 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 doesn’t “rust” 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)

To test for Ag+

1. add 2 drops 6M HCl to 1 mL of unknown sample. Centrifuge (3-4 minutes). Add 1 more drop of 6M HCl and centrifuge (if necessary). A precipitate will form; decant (pour off) solution to another test tube (save solution)

2. wash precipitate from step 1 with 1 or 2 mL of distilled water. Stir, centrifuge, and decant the liquid (can be discarded). Then add 1 mL of distilled water to precipitate and place the test tube in boiling water. Let the test tube boil, and stir occasionally. Centrifuge the hot test tube (solution) and then decant after centrifuging (save the decant solution). Save the precipitate.

3. Add 10 drops of 6M HNO3 to the precipitation from step 2 and stir it. Centrifuge and decant the solution (save it).

4. Add 6M HNO3 to the solution from step 3 until it is acidic toward litmus paper. If Ag+ is present in the acidic solution, a white precipitate of AgCl will form.

To test for Cu2+ and Sb3+

1. Add 15M NH3 to 1 mL of unknown sample until the solution is basic to litmus paper. A precipitate may form at this point due to the formation of insoluble oxychlorides of bismuth, tin, or antimony. Add 1 drop 6M HCL for each mL of solution. Verify the pH level by using methyl violet paper, the paper should turn blue-green. Adjustment may be necessary to achieve the blue-green color. Add HCl or NH3 until it is almost the same blue-green color.

2. Add 15-20 drops of 1M thioacetamide to solution and heat in boiling water for 5 minutes. Centrifuge and decant to another test tube (may contain Fe and Cr). Test solution for completeness of precipitation by adding 2 drops of thioacetamide and letting it sit for 1 minute. If precipitation forms, add a few more drops of thioacetamide solution and heat again. Combine the two batches of precipitate. Wash precipitate with 1 M NH4Cl solution, stir, and warm in bath water; centrifuge, and discard the wash solution.

3. To sulfide precipitate from step 2 add 15 drops of 6M KOH, 2mL of water, and 3 drops 1M thioacetamide. Heat solution in boiling water for 5 minutes and stir occasionally. Centrifuge and decant the solution. Wash any precipitate remaining twice with 5 drops of water and combine the washings with the solution. Tin and antimony will be present in the solution as complex ions, and copper and bismuth will remain as undissolved sulfide precipitate. Save precipitate for later.

4. Add 12 M HCL to the solution from step 3 until it is acidic toward litmus paper. When acidified, some tin and antimony will precipitate as orange sulfides. Add 5 drops of 1M thioacetamide and heat. Centrifuge and decant solution (this solution can be discarded)

5. Add 10-15 drops of 12M HCl to the precipitate from step 4 and heat for 5 minutes to dissolve precipitate. Continue heating until H2S is gone. Centrifuge out any insoluble sulfur residue.

6. Add 0.5 grams of oxalate acid and 2 mL of water to remainder of solution from step 5. Heat the solution, if necessary, to dissolve the oxalate acid. This reagent forms a stable complex ion with Sn4+. Add 10 drops of 1M thioacetamide and heat. Formation of an orange precipitate indicates the presence of antimony.

6. Add 30 drops of 6M HNO3 to remaining sulfide precipitate from step 3. Heat solution gently in boiling water to complete dissolution of the sulfides. Centrifuge the solution to remove sulfur and decant it into a small beaker. Place beaker on hot plate and evaporate the liquid to a volume of about one-half mL. DO NOT LET SAMPLE DRY OUT.

7. Add 15M NH3 dropwise to the solution obtained in step 8 until it is basic toward litmus paper. Add a few more drops. The formation of a deep blue solution indicates the presence of copper.

Testing for Fe3+ and Cr3+

1. [If a solution is being used from which group II cations have been precipitated, remove the H2S and excess acid by boiling the solution in a small beaker until a volume of about 1 mL. Remove any sulfur residue by centrifuging the solution.] [if a solution being used contains only group II ion, then use 1 mL of this solution.]

2. Add 3 drops of 3% H2O2 to 1 mL solution from step 1. Add 15 drops of 6M NaOH to solution to make it strongly alkaline (basic). Stir for 1 minute and boil to remove all excess H2O2. After H2O2 is decomposed, solution will ‘bumb’. If oxidation of chromium (II) has occurred, the solution will be yellow. If not, add 3 more drops of H2O2 and boil again. Centrifuge and decant. Save precipitate (contains Fe3+) and solution (contains Cr3+).

3. Acidify solution from step 2 by adding drops of 15 M HNO3(about 5 drops) and test with litmus paper. Add 6M NH3 drop by drop with mixing until solution is basic. This treatment will precipitate Al3+, will be gelatinous white. May appear yellow because of the presence of CrO42-. Centrifuge and decant the solution, it contains CrO42-. Add 1 M BaCl2 to solution from step 3 to precipitate yellow BaCrO4. If precipitate is slow to form, heat in boiling water. Centrifuge the solution and decant. Dissolve the precipitate in 3 drops of 6M HNO3; heat and stir. Add 4 drops of water and cool it down. Add 6 drops of diethyl ether followed by 1 drop of 3% H2O2. Shake gently, and allow layers to settle. A blue color in ether (top) later confirm test for chromium.

4. Add 8 drops of 15M HNO3 to precipitate from step 2. Heat until precipitate is dissolved. Allow to cool and add 10 drops of 1M NH4Cl and then add 15 M NH3 until solution is alkaline to litmus paper. This will precipitate iron as brown. Then add 4-5 drops of NH3 solution and stir. Centrifuge and decant solution (this solution may be discarded).

5. Dissolve the precipitate from step 5 by adding 10 drops of 6M HCl. Dilute with 2mL of distilled water and add 2 drops of 0.5M KSCN. A blood-red color indicates presence of Fe3+.

-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

I will be given 3 mL of an unknown sample and I will have 75 minutes to do a qualitative analysis for Ag, Cu, Sb, Fe, Cr.

I need help coming up with a flow chart based on the above steps so that it is makes this class assignment smoother since I will only be given 75 minutes to complete it.

Thank you!

I just had a lab on Identification Tes, but i ha some difficulty to understand. If possible can you please help me with this table?

A. Identification Tests

Materials: Three small beakers (100-150 mL), test tubes (6), test tube rack, stining rod,

50-mL graduated cylinder, test tube holder, droppers, boiling water bath, 1 % starch,

10% NaCl, 0.1 M AgN03, 10% glucose, Benedict's reagent, iodine reagent. Dropper

bottles ivith these reagents may be available in the laboratory.

In this experiment, you will perform the identification tests for c1-, glucose, and starch. To determine the

presence or absence of ci-, glucose, or starch in later experiments, refer to the results of the tests. For

each test, observe and record the initial properties of the reagent and the final appearance of the solution

after the reagent is added. In a positive test, there will be a change in the original properties of the

reagent, such as a color change and/or the formation of a precipitate (opaque solid). If there is no change

in the appearance of the reagent, the test is negative.

Caution: AgN03 and iodine reagent stain!

A.1 Chloride (Cr) test Place 3 mL of 10% NaCl in a test tube. Place 3 mL of distilled water in another

test tube. The test tube with the water will be the control or comparison sample. Test for ci- by

adding 2 drops of 0.1 M AgN03 to each. Record your observations. Compare the results for the

NaCl solution with the results for the water sample.

A.2 Starch test Place 3 mL of 1 % starch solution in a test tube. Place 3 mL of distilled water in

another test tube. Add 2-3 drops of iodine reagent to each. Record your observations. Compare the

results for the starch sample with the results for the water sample.

A.3 Glucose test Place 3 mL of 10% glucose solution in a test tube. Place 3 rnL of distilled water in

another test tube. Add 3 mL of Benedict's reagent to the glucose and to the distilled water. Heat

both test tubes in a boiling water bath for 5 minutes. Record your observations. Compare the results

for the glucose with the results for the water sample. Note: Each time you carry out the glucose

test, the test tubes containing Benedict's reagent must be heated in a boiling water bath.

TEST REAGENT ADDED RESULTS OF POSITIVE TEST RESULTS WITH WATER CONTROL
A.1 CI- AgNO3
A.2 starch IODINE
A.3 GLUCOSE BENEDICT'S HEAT

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