Thursday, 1/7

Post-lab analysis. The goal is to determine the identity of the precipitates for each combination that gave a reaction. Once the list is complete, watch the video on writing reactions, and then get started writing the reactions.

General process (note I’m leaving out charges here just because this editor can’t do superscript/subscript):

  1. For all boxes in all sets where you had a PPT, write the new combinations of ions that might be your PPT.
    1. Example: For the intersection of Ba & Cl with Na & CrO4, new combinations could be Ba & CrO4 or Na & Cl.
    2. If a particular combo is already on your list of possibilities, there’s no need to add it again – the goal is to generate a list of unique combinations that might or might not be causing a solid.
  2. Once you have that list, next is to determine which pairs result in solids and which don’t. This behavior for a particular pair of ions is universally consistent – either  they always do, or they always don’t.
    1. Turns out you can’t figure out pairs that do directly – you have to find ones that don’t, and use process of elimination.
      1. Example: Na & Cl also show up in the intersection of Ba & Cl with Na & NO3. There was no PPT there, so Na & Cl don’t make a PPT. Therefore, in my first example, it must be the Ba & CrO4 that made the PPT.
    2. Any pairs you determine make a PPT, put on one list (Yes). Any pairs you determine don’t make a PPT, put on a different list (No).
    3. Your Yes list is the PPTs for your lab.

Handout needed:

  • Get the handout from me tomorrow, or download the handout from Schoology


  • For tomorrow, finish building list of PPTs and watch the video
  • Lab Notebook Q2 due tomorrow!
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