Question

just making sure did I do right in number 10. and im confused at number 11 and 12 13. becausse we didnt learn in class. please help. thanks for your patient

PROCEDURE 1. This experiment is to be conducted individually. on the side shelf: small squares of copper, NaOH, HSO in the hood: conc. HNOs, conc. HC 2. The following items will be found 4 Use your brush and some soap solution to wash your casserole dish as well as reasonably possible. Dry the casserole dish with a paper towel. Obtain a square of copper metal from the side shelf. Weigh both of these items separately to 0.01 g. Record the measurements to the second decimal place. 3 Powdered zinc will be found in the balance room. 5. Label a 250 mL beaker with your name. Place the square of copper metal in the labelled beaker. Take the beaker with copper and a 10.0 mL graduated cylinder to the class hood. Using a 10.0 mL graduated cylinder, pour out 4.0 mL of concentrated nitric acid. Add the 4.0 mL of nitric acid to the copper metal. Gently swirl the beaker and allow the beaker to sit in the class hood until the metal is fully dissolved. All brown fumes are to be emitted inside the class hood. Please be respectful of other students and place your beaker toward the back of the hood while waiting for the copper to dissolve. Avoid releasing the brown fumes into the lab room. Note: When reacting Cue metal, the product usually is Cu ion. Disposal: If you obtain too much nitric acid, put the excess into the waste container. Caution: Concentrated nitric acid is corrosive. Avoid skin contact. If you get the concentrated nitric acid on your skin, rinse well with plenty of water and notify your instructor. Gloves are available for you to use. 6. Add 100.0 mL distilled water to the reaction beaker. Use the 50.0 mL graduated cylinder twice. 7. Add 15.0 mL of dilute NaOH. If you obtain too much NaOH, put the extra into the waste container. Use a dropper and pull some solution into the dropper and observe the solution color. 8. Set up a ring stand with a ring, wire gauze, and burner and heat the solution while stirring. Do not boil! Heat the solution until no blue can be seen in the solution or in the solid. 9. Allow the solid material to settle and carefully pour off the clear liquid above. This is a process called decantation. Keep pouring until the solid at the bottom begins to leave the beaker. Avoid loss of solid. Add about 20 mL of distilled water, settle, and decant once more. The purpose of adding the additional distilled water is to wash the solid and remove the previous solution. Disposal: Put the initial decanted liquid into the waste container. The second 20 mL decant can be put down the drain. 10. Slowly add 30.0 mL of dilute sulfuric acid to the solid material in the beaker. Chem 24A Cu Cycle Revised Sp 17 PROCEDURE 1. This experiment is to be conducted individually. on the side shelt: small squares of copper, NaOH, Hso, in the hood: conc. HNOs, conc. HC 2. The following items will be found 4. Use your brush and some soap solution to wash your casserole dish as well as reasonably possible. Dry the casserole dish with a paper towel. Obtain a square of copper metal from the side shelf. Weigh both of these items separately to 0.01 g. Record the measurements to the second decimal place. Powdered zinc will be found in the balance room. 3 5. Label a 250 mL beaker with your name. Place the square of copper metal in the labellled beaker. Take the beaker with copper and a 10.0 mL graduated cylinder to the class hood. Using a 10.0 mL graduated cylinder, pour out 4.0 mL of concentrated nitric acid. Add the 4.0 mL of nitric acid to the copper metal. Gently swirl the beaker and allow the beaker to sit in the class hood until the metal is fully dissolved. All brown fumes are to be emitted inside the class hood. Please be respectful of other students and place your beaker toward the back of the hood while waiting for the copper to dissolve. Avoid releasing the brown fumes into the lab room. Note: When reacting Cu metal, the product usually is Cu ion. Disposal: If you obtain too much nitric acid, put the excess into the waste container. Caution: Concentrated nitric acid is corrosive. Avoid skin contact. If you get the concentrated nitric acid on your skin, rinse well with plenty of water and notify your instructor. Gloves are available for you to use. 6. Add 100.0 mL distilled water to the reaction beaker. Use the 50.0 mL graduated cylinder twice. 7. Add 15.0 mL of dilute NaOH. If you obtain too much NaOH, put the extra into the waste container. Use a dropper and pull some solution into the dropper and observe the solution color. 8. Set up a ring stand with a ring, wire gauze, and burner and heat the solution while stirring. Do not boil! Heat the solution until no blue can be seen in the solution or in the solid. 9. Allow the solid material to settle and carefully pour off the clear liquid above. This is a process called decantation. Keep pouring until the solid at the bottom begins to leave the beaker. Avoid loss of solid. Add about 20 mL of distilled water, settle, and decant once more. The purpose of adding the additional distilled water is to wash the solid and remove the previous solution. Disposal: Put the initial decanted liquid into the waste container. The second 20 mL decant can be put down the drain. 10. Slowly add 30.0 mL of dilute sulfuric acid to the solid material in the beaker Chem 24A Cu Cycle Revised Sp 17 This is an individual lab. All chemical equations must show the physical states Data: 1. Mass of initial piece of copper O23 2. Mass of clean, empty casserole: 98.659 98-889 3. Mass of casserole and copper 4. Mass of recovered copper: Show calculation: 99.48 Observational Questions: In the copper aycle, several reactions occur. Each reaction is indicated by either a color change or a physical state form. Answer the following questions. 5. The balanced equation for the reaction occurring in step 5 is: +2 HOn Cu(NOa)a 2 NO2g Cu(s) + 4 HNO3(ag) OKidi reod In this reaction, is the copper metal oxidized or reduced? a. HN6 2 b. What is the oxidizing agent in this reaction? c. What is the identity of the gas produced? o d. Describe how the copper changed in this reaction, What colors were seen? What changes in state were seen? CaPfer change fom Soltod to fonic form Cu-Cu Sdution tum blve Tn Colors 2+ FOrmey Sdid Crystels In step #6, the solution was diluted. 6. J04 mL a. Total volume of solution: b. Calculate the molarity of the diluted copper solution. Chem 24A Cu Cycle Revised Sp 17 d. Which of the products of this reaction is likeliest to have produced the blue color? (Flemember that the Culll) lon is blue when it is in water.) Cusor 10. Zinc metal is added in step 11. in woter 9ves bhae Glor Sdution Carefully desoribe all observations. What happened to the solid? Did the solution color change? Was a gas formed? a. The solid tun ed aad farmed gas and bubles The stuetion tun briaht cleor wth red Sdds on b. Write out the correctly balanced equation for the reaction of Zn and CuSO. Predict the physical states. top. Cut aso4 strgle dsplacement Yectn c. What type of reaction is this? d. The equation in 10b does not explain a major observation that you should have made about the reaction. What is this observation? formation Can be obseved. Bulble Given that there was sulfuric acid left over after all the copper had reacted, write a correctly balanced equation for the reaction between sulfuric acid and the zinc. e. Zcs) tHisorca 2s04 Ce)+ Hocg) f. Does this equation explain the major observation that you made? EXPLAIN! observe we can to He 17beratin of Ha gas Dare butble fomation dring the reactin, 11. Concentration HCI is added in step # 11 of the procedure: a. equation with physical states for the reaction taking place between zinc and hydrochloric acid. Given that there was still some zinc left at this point, write the correctly balanced 105 Chem 24A Cu Cycle Revised Sp 17 compounds that were formed of this experiment? What eventualy happened to the zinc products? More than one zinc compound were formed in this experiment. Name all p08sible zine C What i the only substance theoretically remaining in the casserole at the end of the procedure? 12. Calculations a What is the actual mass of the substance remaining in the casserole? b. What is the expected mass of copper at the completion of the cycle? c. What is your percent yield? Show all necessary calculations for full credit! 13. Questions: Describe what happens to the actual yield and the % yield if the following occur a. When decanting the wash water in step 9, a few grains of the solid were lost. Actual yield: % yield: b. Only 0.41 g of Zn powder was added. Actual yield: % yield: c. Not enough HCI is added to react all of the excess zinc powder. Actual yield: % yield: Chem 24A Cu Cycle Revised Sp 17

Answer 1

The answer of question 10 is correct. Brisk effervesence is due to evolution of hydrogen gas.

11b. Zinc sulphate and zinc chloride were formed in this experiment. Both stayed in dissolved form in the reaction vessel.

11c. Reddish brown crystals of Copper are left in the casserole theoretically. Zinc compounds are present in dissolved form.

Please ask all the questions separately so that we can explain everything better.