Qualitative analysis of ionic compounds

 

background [prelab assignment (20 points) due at the beginning of the lab]

if a precipitate forms by mixing the following chemicals in the corresponding row & column, then write "ppt" in the appropriate cell in the below table

 
sodium hydroxide
sodium phosphate
sodium carbonate
sodium   iodide
sodium sulfate
silver nitrate          
lead II nitrate          
cobalt II nitrate          
copper II nitrate          
barium nitrate          
iron III nitrate          
magnesium nitrate          

use the above table in your prelab assignment & lab note book.

design a flowchart (ex1; ex2) to identify each of the unknown ionic compound (in the below table) based on solubility rules and / or the solution's color (hint: all of the below copper II compounds are blue, while the other solutions are colorless) using the chemicals in the above table. include a copy of your flowchart in your lab notebook, so you can use it during the lab.

purpose

evaluate the reliability of the solubility rules

identify the unknown ionic compound in 3 samples based upon their reaction with other known solutions using solubility rules and your flowchart in the prelab assignment.

materials

known aqueous solution (~ 0.1 M) of the chemicals shown in the above table

unknown aqueous solution; possibilities are shown below.  There may be zero, one, or more than one choice from each column.

BaCl2 CuCl2 Na2CO3
Ba(OH)2 Cu(NO3)2 NaI
  CuSO4 NaOH
    Na2SO4

microwell plates [to view reaction]

methods / data analysis

student design:  use flowchart in your prelab to identify your unknown sample.

if a precipitate does not form within a second or so upon adding the 2nd solution, consider it to be not forming a precipitate.  record any color of the precipitate - it *might* be on the ap exam.

 

Content of lab report [ 40 25 points; no revision for this lab report ]

data / observations (20 10 points)

reproduce the 2 copies of the table in your prelab assignment

determine frequency (i.e. %) of agreement / disagreement between your observations versus solubility rules. consider a cloudy (suspension) to be a ppt. 

sequential observations of your analysis to identify the unknown samples

data analysis: (20 15points)

based on the preceding table, what is the reliability of the solubility rules ? refer to your results to support your conclusion. [5 points]

identify the ionic compound in your 3 unknown samples; refer to your flowchart to support your conclusions, e.g. reproduce your flowchart and highlight the path to identifing the unknown ionic compound. [15 points]

selected links

example basis to identify cation & anion

simulation of experimental protocol to identify ions  (see applets for "qualitative analysis of cation / anion)

lab activity source (examples):  site 1  & site 2 [access 4 / 2009]

passsword protected content: flowchart; (no password protection) simulation