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Flame Test

  • Page ID
    150649
  • INTRODUCTION

    In this experiment, you will be performing qualitative identification of alkali, alkaline, and transition metals. For your reference, a table 1 from your lab manual is copied below for your convenience. Before proceeding, however, read through the procedural notes to ensure correct qualitative analysis.

    PROCEDURAL NOTES

    1. Sodium (Na+(aq))is a common contaminant in many solutions. Thus, when testing liquid solutions, a small amount of yellow sodium emission is often observed even when no Na+(aq) was present in the original sample.
    2. Cobalt glass (Co(s)) is a blue glass useful for masking yellow (sodium) emission. This can be especially useful for identifying elements that weakly emit blue and/or violet.
    3. Liquids or solids can be tested simply by introducing the sample into the flame. Whatever instrument is used to introduce the sample must impart no color itself. Therefore, in this experiment, Nichrome metal loops are used.

    table1ft.png


    PROCEDURE:

     


    Step 1

     

    For each cation to be tested there will be a pair of test tubes. One will contain water and the Nichrome wire; the other tube will contain the cation solution. When doing all the flames tests, only use each wire in the solution that is next to in order to avoid contamination.

    step1ft.png


     

    Step 2

    step2ft.pngstep2liconfigft.png

    Place a bit of LiCl(s) powder onto a clean Nichrome wire. Then, place the wire and crystal in the flame right above the dark blue center of the fire. The color of the flame will change due to emission from the Li+ ions. Observe the color and record in your notebook.


     

    Step 3

    step3NaClft.pngstep3Naconfigft.png

    Now, using NaCl(aq) solution, dip the Nichrome wire in the cationic solution. Then, place the wire in the flame just above the dark blue center of the fire. Be sure to record your observations in your lab notebook - be very descriptive.


     

    Step 4

    step4potassiumft.pngs4 K configuration ft.pngUsing KCl(aq) solution, dip the Nichrome wire in the cationic solution. Then, place the wire in the flame just above the dark blue center of the fire. Be sure to record your observations in your lab notebook - be very descriptive. Note that K+(aq) can be difficult to observe, so you may need to use cobalt glass (Co(s)).


    Step 5

    s5CuSO4ft.pngs5 Cu configurationft.png

    Using CuSO4(aq) solution, dip the Nichrome wire in the cationic solution. Then, place the wire in the flame just above the dark blue center of the fire. Be sure to record your observations in your lab notebook - be very descriptive.


    Step 6

    s6 Sr(NO3)2(aq) ft.pngs6 Sr configurationft.png

    Using Sr(NO3)2(aq) solution, dip the Nichrome wire in the cationic solution. Then, place the wire in the flame just above the dark blue center of the fire.

    Be sure to record your observations in your lab notebook - be very descriptive.

     


    Step 7

    Unknown Crystals: Repeat the flame test steps using a small unknown crystal from the previous experiment as the sample. Use a clean, uncontaminated wire from the provided beaker. Record your observations in your notebook and use the results of the previous tests to determine which metal ions (if any) are present in the unknown crystals.

    s7unknown crystals ft.png


     

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