I have a prac test that is about using precipiation reactions to identify 4 unknown solutions. We will be given the names of the solutions but we need to allocate the right name to the correct solution. I was wondeing what would be the best way to approach doing this prac?
Hey Anotherworld2b!
You definitely asked the right person, because I did the same prac exam as you in term 1 with 5 unknown solutions. I scored 25/25 in that exam and this one simple table trick I will show you below has really helped me! So essentially how it works is you construct two tables. You will be given on the day what all the four chemicals are, except you dont really know what each individual chemical is. So on one table, you will be constructing a table like what I have shown below, with your different unknown chemicals and the outcomes of the reactions (i.e. whether there are precipitates or not). This is your experimental data.
On another table, you will be constructing a table like what I have also shown below, with your different KNOWN chemicals and the outcomes of the reactions (i.e. whether there are precipitates or not). This is your theoretical data obtained through your solubility rules.
So now what we do is we match the outcomes. For instance, whichever chemical in the first table that is able to form 2 precipitates should be matched to whichever chemical in the second table that is also able to form 2 precipitates. This way we can identify that the two chemicals are the same and hence identify the unknown chemical as I have shown below.
But now, sometimes you can get situations where you have 2 chemicals from the first table that can form equal amounts of precipitates. Teachers shouldnt give you this sort of situations but if this situation does happen, normally it would not matter which one you would identify as the correct chemical. But, there can be special cases, like what I have shown below, that can help you to determine the correct chemical when two particular chemicals can form equal amounts of precipitates.
I hope my guide helps, and I certainly really enjoyed writing this explanation and I really hope you can achieve a high mark by following what I suggested above!
Best Regards
Happy Physics Land