Two beakers were used in an experiment each with 100g of water at 30 degrees C. To the first beaker, 90g of NaNO3 was added. To the second beaker, 90g of KNO3 was added. (a)Which beaker had the salt precipitate out (settle to the bottom) and how much? (b) Which beaker could hold more salt and how much could still be added?
Surely you have a table giving you the solubilities of these two salts at 30 C. Or perhaps you are supposed to look them up. At any rate, you must have the data to determine the answers.
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To determine which beaker had the salt precipitate out and how much, we need to compare the solubility of NaNO3 and KNO3 in water. The solubility is the maximum amount of a solute that can dissolve in a given quantity of solvent at a specific temperature.
(a) Beaker 1 with NaNO3:
The solubility of NaNO3 is approximately 1,371 g/L at 30 degrees C. Since we started with 100 g of water in the beaker, we need to check if the addition of 90 g of NaNO3 exceeds its solubility.
To do this, we calculate the maximum amount of NaNO3 that can dissolve in 100 g of water at 30 degrees C using the solubility value:
Maximum amount of NaNO3 = 1,371 g/L * (100 g / 1,000 mL) = 137.1 g
Since we added only 90 g of NaNO3, which is less than the calculated maximum amount, none of the salt will precipitate out in Beaker 1.
(b) Beaker 2 with KNO3:
The solubility of KNO3 is approximately 321 g/L at 30 degrees C. Again, we need to check if the addition of 90 g of KNO3 exceeds its solubility.
The maximum amount of KNO3 that can dissolve in 100 g of water:
Maximum amount of KNO3 = 321 g/L * (100 g / 1,000 mL) = 32.1 g
Since we added 90 g of KNO3, which is greater than the calculated maximum amount, some of the salt will precipitate out in Beaker 2.
To determine how much salt precipitated out in Beaker 2, we need to find the difference between the amount added (90 g) and the maximum amount that can dissolve (32.1 g):
Salt precipitated out = 90 g - 32.1 g = 57.9 g
Therefore, (a) no salt precipitates out in Beaker 1, and (b) in Beaker 2, 57.9 g of salt precipitates out.
Now moving on to the second part of the question, which beaker could hold more salt and how much could still be added:
Since we calculated the solubility for both NaNO3 and KNO3, we can compare these values to determine which salt could be added in larger quantities.
The solubility of NaNO3 (1371 g/L) is higher than the solubility of KNO3 (321 g/L) at 30 degrees C. This means that NaNO3 has a higher capacity to dissolve in water. Therefore, Beaker 1 could hold more salt, as it has a higher solubility.
Since we didn't reach the solubility limit for NaNO3 in Beaker 1 (only 90 g added), more NaNO3 could still be added until it reaches the solubility limit. Therefore, Beaker 1 has the potential to hold more salt.