Presentation on theme: "CHM 101/102 Laboratory Manual Exchange Reactions General Chemistry 101/102 Laboratory Manual University of North Carolina at Wilmington."— Presentation transcript:
CHM 101/102 Laboratory Manual Exchange Reactions General Chemistry 101/102 Laboratory Manual University of North Carolina at Wilmington
CHM 101/102 Laboratory Manual Exchange Reactions Purpose Purpose To study exchange reactions and learn more about the descriptive chemistry of common chemical compounds. Safety Considerations Safety Considerations Avoid directly smelling any of the substances in this experiment. Use the wafting technique to detect odors. If one of your unknowns is (NH 4 ) 2 S, work with it in the hood. Pour all waste materials into the appropriately labeled containers in the hood.
CHM 101/102 Laboratory Manual Exchange Reactions Procedure Procedure Your lab instructor will give you a list of 10 compounds from which your set of 5 unknowns will be drawn. On the back of this list are the numbers representing your unknowns. Copy the front and back of the list in your lab book and return the list to your instructor. NaNO 3 KCl Pb(NO 3 ) 2 BaCl 2 KI Na 2 SO 4 K 2 CO 3 AgNO 3 K 2 CrO 4 CuCl 2 Set #4 5 8 23 18 12 frontback
CHM 101/102 Laboratory Manual Exchange Reactions Procedure Procedure All glassware and plasticware used in this experiment must be clean and rinsed with deionized water to avoid contaminating your unknowns and producing false positive test results. Label 5 test tubes. Place 3 mL of each of your unknowns in the appropriate test tubes using the pipets supplied with the unknowns. Be sure to return the pipets to their correct containers. approximately 3 mL
CHM 101/102 Laboratory Manual Exchange Reactions Procedure Procedure Observe and record the color of each of your unknowns. This is important evidence of what is and what is not in your unknown. Determine the odor of each of your unknowns. This test is performed by wafting vapors from your unknown toward your nose. wafting technique 1 ft If your unknown contains Na 2 S (rotten egg odor), perform all tests with this substance in the hood.
CHM 101/102 Laboratory Manual Exchange Reactions Procedure Procedure Test the acidity and basicity of each of your unknowns using red and blue litmus paper. Perform the litmus tests as shown in these photos. Do not dip litmus paper into the test tube containing your unknown. Be careful in interpreting the results of litmus tests with colored solutions. acids turn blue litmus red bases turn red litmus blue
CHM 101/102 Laboratory Manual Exchange Reactions Procedure Procedure Write the numbers of your unknowns along the top and down the side of the 5 x 5 reaction matrix. Perform each test in a spot plate well and record the colors of any precipitates formed. yellow ppt brown ppt NR NR NR NR white ppt lt. blue ppt white ppt
CHM 101/102 Laboratory Manual Exchange Reactions Procedure Procedure If your unknown set contains both Cu(NO 3 ) 2 and CuSO 4, you may need to perform an additional test using BaCl 2 to distinguish between them. Identify each unknown in your set using the data you collected on color, odor, acidity/basicity, and precipitate formation. Write a balanced chemical equation for each reaction that produced a precipitate. K 2 CrO 4 (aq) + Pb(NO 3 ) 2 (aq) PbCrO 4 (s) + 2 KNO 3 (aq) yellow
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