Solubility Curve Lab

Today in 7th Period Chem we did yet another lab! This one dealt with measuring the saturation temperatures for six difference solution concentrates to construct a solubility curve.

The lab itself wasn't too complicated. Each lab group had 6 test tubes: 3 for Series 1 and 3 for Series 2. The first step was to mass the empty test tubes and record that in the lab table. Next, we added potassium nitrate to each test tube: each test tube had a specific amount of potassium nitrate it needed to be added [the lab direction sheet explains the specifics]. Once that was done, we massed the test tubes with the potassium nitrate and added that in the data table. The next step was to add 20 drops of distilled water into each test tube. Then -you guessed it- we massed the test tube plus potassium nitrate plus water....and added that into our data table. Finally, we placed the test tubes in a hot water bath, letting the potassium nitrate dissolve, then put the test tubes in an ice water bath. This cooled the solution which enabled it to crystallize. We took note of the temperature the instant crystallization occurred and recorded that into our lab table.

With all this information, there were some things that needed to be calculated in the lab. The calculations were quite simple- you just needed to use your data.

1. Calculate the mass of potassium nitrate and the mass of water in each solution

For the mass of potassium nitrate, you take the mass of test tube and KNO3 and subtract it by the mass of the empty test tube. So essentially, the second column of your data table minus the first. You have to do that for all 6 of the test tubes, so it gets pretty tedious.

For the mass of water, it's the same idea. Subtract the mass of test tube plus KNO3 and water by the mass of test tube and KNO3, which is really column 3 in your data table minus column 2.

2. Calculate the ratio of the mass of potassium nitrate to the mass of water for each solution

Here, you take the values you got from part one and set them to a ratio. For each of the 6 test tubes, divide the mass of potassium nitrate by the mass of water. That will be your ratio.

3. Multiply each ratio by 100 to get the solubility in g/100g of solvent

This one speaks for itself. Multiply what you got in in part two by 100 and you're set.

So that's the gist of the lab and the calculations. After you do that, all you have to do is place ALL of the results in a results table and plot a graph of solubility of potassium nitrate!

This lab is due Monday.

Other than that, we have a Webassign due tomorrow as well as the usual worksheets that will be due at the end of the unit.

That's all I've got for today. The next scribe will be.............................................NIRALI P! Good luck :)