A student adds 50 g of KNO3 to 50 mL of water at 60 degrees C. The solution is cooled to 10 degrees C and then poured through a piece of 2 g filter paper in a funnel which is dried overnight. What is the predicted mass of the dried filter paper and solid?
The predicted mass of the dried filter papre and solid is about 40 g.
So, you know that you're dissolving 50 g of potassium nitrate,
The first thing you need to determine is whether or not you can dissolve that much potassium nitrate in that much water. To do that, use potassium nitrate's solubility curve, which looks like this
Notice that, at
So, at this temperature, you can dissolve
in that muc hwater. Since you have less potassium nitrate than that, your solution will be unsaturated.
When you cool the solution to
This means that the excess potassium nitrate will precipitate out of the solution. At
Therefore, the mass of the precipitate will be
Adding the mass of the dried paper filter will get you
Rounded to one sig fig, the answer will be