Cu-AgNO 3 Lab Date: Hour: Question: What is the mole ratio of copper consumed to silver produced in the reaction?

Transcription

1 Chemistry Cu-ANO 3 Lab Name: Date: Hour: Partner: Question: What is the mole ratio of copper consumed to silver produced in the reaction? Hypothesis: (answer usin complete sentences) Research (answer questions in complete sentences) 1. This is a sinle displacement reaction. What happens durin a sinle displacement reaction? 2. We will make an aqueous solution durin this lab. Read throuh the procedure and answer these questions: a. What is an aqueous solution? b. What will our solute be? c. What will out solvent be? 3. Read throuh the procedure. Draw what you think the set-up for the lab will look like: 4. Write out the word equation for what should happen durin the lab. (The reactants are silver nitrate and copper wire.) 5. What is the formula for silver nitrate? (NOTE: Silver has a 1+ chare.) 6. Copper can form two oxidation states, Cu + and Cu 2+. What are the two possible formulas for copper nitrate we miht form in this lab?

2 7. Write out and balance the two possible reactions that miht happen in this lab, one formin copper (I) nitrate and one formin copper (II) nitrate. Materials (DON'T copy into your lab book): 1 piece of copper wire 1 balance 2 beakers 1 test tube brush 1 permanent marker 1 20 x 150 mm test tube 1 bottle of distilled water 1 lass stirrin rod (may have rubber) 1 test tube clamp 1 rinstand 1 25 ml raduated cylinder 1 stopwatch 1 pair of loves 1 piece of steel wool 1 ruler Procedure 1. Physically and chemically clean the beakers, test tube, stirrin rod, and raduated cylinder. 2. Dry one of the beakers. (The other items may be damp.) 3. Label the dry beaker silver, your initials, and your class hour with the permanent marker (NOT on the white or blue part or the lines) 4. Put on loves. 5. Obtain a lenth of copper wire and a massin cup containin silver nitrate from the teacher. 6. Record the balance number. (USE THE SAME BALANCE FOR ALL MASSES.) 7. Mass the copper wire. 8. Mass the massin cup of silver nitrate. 9. Clamp the clean 20 x 150 mm test tube to the rin stand. 10. Add about 20 ml of distilled water to the test tube usin the raduated cylinder. 11. Add the silver nitrate from the massin cup to the test tube. (You may bend the massin cup.) 12. Stir ently to dissolve the crystals. 13. Rinse the stirrin rod with a small amount of distilled water into the test tube when you are done stirrin the solution. 14. Coil the copper wire by wrappin it around a pencil. 15. Stretch the wire until it is about 2 cm loner than the test tube. 16. Place the coiled wire into the test tube with the silver nitrate solution so that the straihtened end is out of the solution. 17. Note the reaction that occurs; record your observations. 18. Allow the reaction to continue for 10 minutes, then ently shake the silver crystals from the copper wire to expose more copper wire. 19. Allow the reaction to continue for an additional 10 minutes, then ently shake the silver crystals from the copper wire to expose more copper wire. 20. Find the mass of the empty massin cup. 21. Return the massin cup to the teacher. 22. If possible, allow the reaction to occur for an additional 10 minutes (total of 30 minutes). 23. Shake the silver crystals from the copper wire. 24. Gently remove the wire from the test tube.

3 25. Usin the distilled water bottle, rinse the wire into the massed, labeled beaker. 26. Pour the contents of the test tube into the labeled beaker (you may need to use distilled water to rinse it out). 27. Dip the copper wire in acetone in the fume hood, then set it aside to dry on a paper towel. 28. When the copper wire is dry, find its mass, then put it in the waste jar. 29. Label the second beaker WASTE with the permanent marker. 30. Carefully decant (pour off) the solution from the silver crystals into the WASTE beaker. 31. Measure out 10 ml of distilled water with the raduated cylinder. 32. Rinse the silver with about 10 ml of distilled water, stirrin ently with the stirrin rod. 33. Allow the silver to settle, then decant (pour off) into the WASTE beaker. 34. Repeat steps three more times (for a total of FOUR washes). (Don t worry about the few tiny particles of silver that float off as you decant. Their mass is neliible.) 35. After the final rinse, place the labeled beaker with silver in the dryin oven. 36. Pour all the liquid from your WASTE beaker into the waste jar. 37. When the silver is dry, find the mass of the beaker and silver usin the same balance as on Day 1. Data: balance # mass of labeled beaker mass of cup + ANO3 mass of Cu wire before mass of empty massin cup mass of Cu wire after mass of beaker + dry A Calculations 1. Determine the mass of copper that reacted durin the experiment. 2. Convert this mass of copper to moles of Cu. 3. Determine the mass of silver produced durin the experiment.

4 4. Convert this mass to moles of A. 5. Determine the value of the ratio: molesa. Be sure to use the appropriate sinificant molescu fiures! 6. Determine the mass and then the number of moles of ANO3 used in the lab. 7. Determine the value of the ratio: fiures! moles A moles ANO 3. Be sure to use the appropriate sinificant

5 Conclusion 1. Because of our deep and abidin belief that atoms react in simple inteer ratios, what do you moles A produced suppose is the actual ratio of molescu consumed? You should use class results to help you decide the correct value. From your answer, write the balanced equation for the reaction between copper and silver nitrate. 2. Make a BCA table for this chemical reaction. Enter the value of moles of ANO3 in the before line and xs for moles of Cu. In the chane line, enter the moles of Cu reacted. Now, use the moles of Cu to complete the table. 8. Next, determine the theoretical yield of mass of A. From your actual mass of A and the theoretical yield, determine the % yield. moles A produced 3. If your ratio is reater than the accepted value, then either the moles of A molescu consumed is too hih, or the moles of Cu is too low. If your ratio is lower than the accepted value, then either the moles of A is too low, or the moles of Cu is too hih. Use the % yield to help you decide whether the problem is due to the value you have obtained for the moles of silver. List at least one specific experimental error that could account for ratio bein too hih or too low. moles A 4. It is possible that your value of the ratio is less than 1.00 even if your ratio moles ANO 3 moles A produced is acceptable. Assumin that you did not lose silver durin decantin, what molescu consumed could account for a ratio bein smaller than one?