1) If 358 g of KNO3 are dissolved in 650 mL of water at 80°C, at what temperature will solid settle out when it is cooled?
2) Give 2 ways, quantitatively, that a solution of 80 g of NaNO3 in 100 mL of water at 70°C can be made saturated.
3) If 100 g of KClO3 is dissolved in 500 g of water at 80°C, how much more salt must be added to make the solution saturated?
4) a. If a solution containing 40.0 g of KNO3 in 100 g of water at 100°C is cooled to 25°C, how much of the solid will settle out?
b. If you poured out half of the solution in (a) at 100°C, how many grams of the solid will the remaining solution contain?
c. If instead of pouring out as in (b), you boil away 50 mL of water and return the to 25°C, how many grams of solid will now remain in the solution?
Can someone help answer those questions pls
And have you given these a try?
yes. and the only one I am stuck on is 4
1) To find the temperature at which solid will settle out when the solution is cooled, we can use the concept of solubility. When a solution is saturated, it contains the maximum amount of solute that can dissolve at a given temperature. So, when the temperature is decreased, the solute will begin to solidify and settle out.
To determine the temperature at which the solid will settle out, we need to find the solubility of KNO3 at various temperatures. This information can be found in a solubility chart or a reference book.
Once we have the solubility values, we compare them to the initial concentration of KNO3 in the solution. When the concentration exceeds the solubility, the excess solid will start to settle out. In this case, we can calculate the temperature at which the solubility of KNO3 is exceeded, causing solid to settle out.
2) To make a solution saturated, we need to add enough solute to reach the maximum solubility at a specific temperature. Here are two ways to quantitatively prepare a saturated solution of NaNO3:
- Method 1: Use the solubility table to find the maximum solubility of NaNO3 in water at the desired temperature. Weigh out 80 g of NaNO3 and add it to a container. Gradually add 100 mL (or slightly less) of water while stirring until the solute is completely dissolved. This will give you a saturated solution.
- Method 2: Calculate the amount of water needed to dissolve 80 g of NaNO3 at a specific temperature using the solubility information. Let's say the solubility of NaNO3 is 100 g/100 mL at that temperature. Use the formula: (Desired mass of solute / Solubility of solute) x Volume of solvent = Volume of water required. Substituting the values, we get: (80 g / 100 g) x 100 mL ≈ 80 mL. So, measure 80 mL of water and dissolve the 80 g of NaNO3 in it to obtain a saturated solution.
3) To determine how much more salt must be added to make the 100 g KClO3 solution saturated, we need to compare the current concentration with the solubility of KClO3 at the given temperature. We can use the same approach as in the previous questions by referring to a solubility chart or reference book.
Let's assume the solubility of KClO3 in water at 80°C is 150 g/100 g. If our 100 g solution is not saturated, it means we need to add more KClO3 until the concentration exceeds the solubility.
To find out how much more salt is needed, subtract the current mass of KClO3 in the solution from the solubility limit. In this case, it would be: 150 g - 100 g = 50 g. Therefore, you would need to add an additional 50 g of KClO3 to make the solution saturated.
4) a. To determine how much of the solid KNO3 will settle out when the solution is cooled, we need to compare the solubility of KNO3 at 25°C with its initial concentration at 100°C. We can find solubility information for KNO3 in a solubility chart or reference book.
Let's assume the solubility of KNO3 at 25°C is 50 g/100 g. If the initial concentration is 40.0 g KNO3 in 100 g of water, which is lower than the solubility, all of the solute will remain dissolved when the solution is cooled.
b. If you pour out half of the solution at 100°C, the remaining solution will contain half of the initial mass of KNO3. So, the remaining solution would contain 20.0 g of KNO3.
c. If you boil away 50 mL of water from the remaining solution and then cool it to 25°C, we need to recalculate the concentration of KNO3. First, calculate the mass of water boiled away by multiplying the density of water (assume 1 g/mL) by the volume boiled away (50 mL): 1 g/mL x 50 mL = 50 g.
Since we started with 100 g of water, the remaining water after boiling will be 100 g - 50 g = 50 g. Therefore, the final solution contains 50 g of water and 20.0 g of KNO3.
Note: These calculations assume ideal behavior and complete dissolution of the solute. In reality, other factors such as impurities and incomplete mixing can affect the results.