DATA TABLE 2: SPOT TESTS OF SUPERNATANT SAMPLES FROM REACTION TUBES

Substance Added Tube 1 Ppt.? Tube 2 Ppt.? Tube 3 Ppt.? Tube 4 Ppt.? Tube 5 Ppt.? Tube 6 Ppt.?
Pb(NO3)2 yes yes no no no no
NaI no no no yes yes yes
reagent present in excess
How do I identify whether or not reagent present in excess?

Hello! I did this same lab today, and we were able to identify the reagent present in excess if a precipitate formed.

To identify whether or not the reagent is present in excess, you need to analyze the data in the table. For the given table, the reagent in question is NaI. Here are the steps to identify if NaI is present in excess:

1. Look at the column for Tube 1 Ppt., Tube 2 Ppt., Tube 3 Ppt., Tube 4 Ppt., Tube 5 Ppt., and Tube 6 Ppt.
2. In each row, check if there is a "yes" or "no" for the corresponding tube.
3. Focus on the rows that correspond to the substance added being NaI.
4. In this case, we're interested in Tubes 4, 5, and 6, as NaI was added in those tubes.
5. If there is a "yes" for Tube 4 Ppt., Tube 5 Ppt., and Tube 6 Ppt., it means a precipitate was formed in all three tubes when NaI was added. This indicates that NaI is present in excess because it reacted with the substance and formed a precipitate each time.
6. On the other hand, if there is a "no" for any of the three tubes (Tubes 4, 5, or 6), it means no precipitation occurred when NaI was added. This suggests that NaI is not present in excess and may have reacted completely with the substance already.

In summary, to determine if the reagent (NaI) is present in excess, you need to examine whether a precipitate forms when NaI is added to the different reaction tubes. If a precipitate forms consistently in all tubes, it indicates an excess of NaI.