You have a 35.5 g of a saturated solution of potassium nitrate at 80oC which you cool to
40oC, what mass of potassium nitrate will precipitate out of solution?
@80 degrees C solubility is 160g solute/100g H2O
@40 degrees C solubility is 60g solute/100g H2O
normally, solubility would be read from a graph.
you dont have 100g aolution, you have 35.5/100 th, so at 80C, you have 35.5/100*160 grams in solution, which is 56.8g KNO3
now at 40C, you can only have 60*(35.5/100) grams in solution,or 21.3 grams in solution.
How much came out of solution?
56.8-21.3=....
To find out how much potassium nitrate will precipitate out of the solution, we need to calculate the difference between the mass of the solute at 80°C and the mass of the solute at 40°C.
First, we need to calculate the solubility in grams of potassium nitrate at both temperatures.
At 80°C:
The solubility of potassium nitrate is 160g of solute per 100g of water.
So, if we have 35.5g of the saturated solution, the amount of solute (potassium nitrate) in it is:
(35.5g * 160g solute) / 100g H2O = 56.8g of solute.
At 40°C:
The solubility of potassium nitrate is 60g of solute per 100g of water.
So, the amount of solute that can remain in the solution at 40°C is:
(35.5g * 60g solute) / 100g H2O = 21.3g of solute.
Now, we can find the mass of potassium nitrate that will precipitate out by subtracting the amount of solute at 40°C from the amount at 80°C:
56.8g - 21.3g = 35.5g of potassium nitrate will precipitate out of solution.
Therefore, 35.5g of potassium nitrate will precipitate out of the solution when it is cooled from 80°C to 40°C.