The solubility of KNO3 is 155 g per 100 g of water at 75 degrees celcius and 38.0 g at 25 degrees celcius. What mass (in grams) of KNO3 will crystallize out of solution if exactly 100 g of its saturated solution at 75 degrees celcius is cooled to 25 degrees celcius.
i found that 60.8 g KNO3 is in the solution at 75degrees, and 27.5 g KNO3 at 25degrees. so 33.3 g would crystallize, but the right answer is 45.9 g. Not sure how to do the problem then...
ever mind...i got it.
To solve this problem, you need to calculate the difference in the amount of KNO3 dissolved at 75 degrees Celsius and 25 degrees Celsius. The solubility of KNO3 decreases as the temperature decreases.
First, calculate the amount of KNO3 dissolved at 75 degrees Celsius:
Solubility at 75 degrees Celsius = 155 g/100 g of water
Amount of water at 75 degrees Celsius = 100 g
Therefore, the maximum amount of KNO3 that can dissolve at 75 degrees Celsius is (100 g water) * (155 g KNO3/100 g water) = 155 g KNO3.
Next, calculate the amount of KNO3 dissolved at 25 degrees Celsius:
Solubility at 25 degrees Celsius = 38.0 g/100 g of water
Amount of water at 25 degrees Celsius = 100 g
Therefore, the maximum amount of KNO3 that can dissolve at 25 degrees Celsius is (100 g water) * (38.0 g KNO3/100 g water) = 38.0 g KNO3.
The difference between the amount of KNO3 dissolved at 75 degrees Celsius and 25 degrees Celsius is:
155 g KNO3 - 38.0 g KNO3 = 117 g KNO3.
However, since the initial solution at 75 degrees Celsius only contains 60.8 g KNO3, not all of the available KNO3 will crystallize out of solution.
The amount of KNO3 that will crystallize out of the solution is the difference between what is dissolved at 75 degrees Celsius and what remains dissolved at 25 degrees Celsius:
117 g KNO3 - 27.5 g KNO3 = 89.5 g KNO3.
Therefore, approximately 89.5 grams of KNO3 will crystallize out of the solution when it is cooled from 75 degrees Celsius to 25 degrees Celsius.
To solve this problem, we can use the concept of solubility and calculate the difference in the amount of KNO3 dissolved in water at 75 degrees Celsius and 25 degrees Celsius.
First, let's find the amount of KNO3 dissolved at 75 degrees Celsius. The solubility of KNO3 at this temperature is given as 155 g per 100 g of water. So, if we have 100 g of water, we can dissolve:
155 g KNO3 / 100 g water * 100 g water = 155 g KNO3
Therefore, the amount of KNO3 dissolved at 75 degrees Celsius is 155 g.
Next, let's find the amount of KNO3 dissolved at 25 degrees Celsius. The solubility of KNO3 at this temperature is given as 38.0 g per 100 g of water. Again, if we have 100 g of water, we can dissolve:
38.0 g KNO3 / 100 g water * 100 g water = 38.0 g KNO3
Therefore, the amount of KNO3 dissolved at 25 degrees Celsius is 38.0 g.
Now, to find the mass of KNO3 that will crystallize out when the solution cools from 75 degrees Celsius to 25 degrees Celsius, we need to calculate the difference in the amounts dissolved:
Mass crystallized = Amount at 75 degrees Celsius - Amount at 25 degrees Celsius
Mass crystallized = 155 g - 38.0 g
Mass crystallized = 117 g.
So, the correct answer is 117 g, not 45.9 g as mentioned. It seems there may have been a calculation error or misunderstanding in the conversion of the given data. Double-checking the calculations should help you arrive at the correct answer.