A 175-g sample of water is saturated with KNO3 at 40ºC. What mass of KNO3 forms a precipitate if the solution is cooled to the freezing point of water? (Refer to the Solubility and Temperature graph.)
Marie, I'll let you in on a little secret. There aren't many people who have the millions of solubility graphs/tables memorized. If you can read the table/graph and post that with your question, someone here will be able to help.
To determine the mass of KNO3 that forms a precipitate when the solution is cooled to the freezing point of water, we can refer to the solubility and temperature graph.
First, we need to understand how to read the graph. The solubility and temperature graph shows the relationship between the solubility of a substance (in this case, KNO3) and the temperature. The solubility is typically measured in grams of solute per 100 grams of solvent, usually water.
On the graph, the x-axis represents temperature, and the y-axis represents solubility. Each point on the graph indicates the maximum amount of solute that can dissolve in the solvent at a specific temperature.
Now let's find the solubility of KNO3 at 40ºC on the graph. Locate the point on the graph where the temperature is 40ºC, and then find the corresponding solubility value on the y-axis.
Once you have determined the solubility, it means that at 40ºC, the maximum amount of KNO3 that can dissolve in 100g of water is the solubility value you found. This allows us to calculate how much KNO3 can dissolve in 175g of water at 40ºC.
To do this, we can set up a proportion:
(Solubility of KNO3 in 100g of water) / 100g = (Amount of KNO3 that can dissolve in 175g of water) / 175g
Solving for the "Amount of KNO3 that can dissolve in 175g of water," we have:
Amount of KNO3 that can dissolve in 175g of water = (Solubility of KNO3 in 100g of water) * (175g / 100g)
Now that we know the maximum amount of KNO3 that can dissolve in the 175g of water at 40ºC, we can subtract it from the initial mass of KNO3 in the solution to determine the mass of KNO3 that will form a precipitate.
So the mass of KNO3 that forms a precipitate if the solution is cooled to the freezing point of water is equal to the initial mass of KNO3 minus the mass of KNO3 that can dissolve in the 175g of water at 40ºC.