I'm supposed to do this for an organic chemistry prelab. I've read my books and tried Googling everything possible, but I still don't know how to set this up. Please help!
The solubility of a certain compound in ice-cold water is 0.18g in 100 mL. Its solubility in hot water is 2.35g in 100 mL. What is the best possible percent recovery we can expect for recrystallization of this compound from water?
You don't have enough information posted to work the problem. Here is what you do.
Look at your procedure and calculate the grams of product you expect to make assuming 100% for the reaction. Then multiply 0.18 x (volume you expect/100) and subtract from the product you expect to have. Finally, the amount left/amount expectedt)*100 = maximum recovery you can expect. You won't get that because the reaction won't be 100%. The idea is that if the solubility is 0.18 g/100 mL, you will lose that much per 100 mL during recrystallization (if just one recryst is done). If you expect to recrystallize more than once, you will lose that much each time.
I've had second thoughts about this. Although I think my initial response is correct, I believe we can approach it another way much simpler.
If we take a 2.35g sample, we can dissolve it in 100 mL water. If we then crystallize it at ice cold temperature, 0.18g of it will be lost. So the amount recovered is 2.35-0.18 =2.17g
%recovery = (2.17/2.35)*100 = x or about 92%
To determine the best possible percent recovery for recrystallization of a compound from water, we need to compare the solubility of the compound in the two different temperatures of water: ice-cold water and hot water.
The percent recovery is the amount of compound recovered divided by the initial amount of compound multiplied by 100.
First, let's calculate the amount of compound that would dissolve in the hot water. We are given that the solubility in hot water is 2.35 g in 100 mL.
Next, we calculate the amount of compound that would dissolve in the ice-cold water. We are given that the solubility in ice-cold water is 0.18 g in 100 mL.
To find the maximum possible recovery, we assume that all of the compound in the hot water solution is recovered. Therefore, the amount of compound recovered is 2.35 g.
Now, we need to calculate the percentage of recovery. We'll use the formula:
Percent recovery = (Amount of compound recovered / Initial amount of compound) * 100
We don't have the initial amount of compound explicitly mentioned in the question. However, we can assume that we start with 100 mL of water in both cases, and the solubility is given as grams per 100 mL.
So, the initial amount of compound in both cases would be equal to the solubility values:
Initial amount of compound in hot water = 2.35 g
Initial amount of compound in ice-cold water = 0.18 g
Let's substitute these values into the formula:
Percent recovery = (2.35 g / 2.35 g) * 100
Percent recovery = 100%
Therefore, the best possible percent recovery we can expect for recrystallization of this compound from water is 100%.