The solubility of a compound is 59g per 100mL in boiling methanol and 30g per 100mL in cold methanol, whereas its solubility in water is 7.2g per 100mL at 95C and 0.22g per 100mL at 2C. Which solvent would be better for recrystallization of the compound? Explain
I am not quite sure how to start it out.
Just like any percent.
In this case, you get 29 g (59-30) back in the cold methanol and you started with 59g; therefore,
%rec =(29/59)*100 = 49% recovered. 51% is lost. (We could have chosen any number to start that we wanted and used proportions to determine how much was soluble at the higher T and how much was soluble at the lower T, but why makes things hard? I just chose 59 g so we KNOW that will dissolve and will leave 29 g at the end. )
In methanol, almost half still is dissolved in cold methanol.
In water, only three percent is still dissolved.
Besides, who wants to stir boiling methanol?
If percent recovery is not an issue, either solvent will work ok. However, note that using methanol loses half the product. From a personal standpoint, I would choose water. It is less soluble BUT the loss is very low.
I sort of see it now. I was wondering what is the formula used to calculate the percent recovery?
If biphenyl dissolves in both cold and hot methanol, would this be a good recrystallization solvent for biphenyl? Explain please!!!
Well, well, well. It seems like this compound has quite the personality when it comes to solubility. Let me break it down for you in my own hilarious way.
In boiling methanol, it can dissolve up to 59g per 100mL. That's like having a buffet and this compound is hogging all the dishes! But when it comes to cold methanol, it's a little pickier. It only wants 30g per 100mL, not as impressive, but hey, we all have our preferences.
Now let's talk about water. At a toasty 95°C, this compound is willing to party and dissolve a whopping 7.2g per 100mL. It's like it's saying, "I'm feeling hot, hot, hot!" But when things cool down to 2°C, it becomes a total freeze-bot and only dissolves a measly 0.22g per 100mL. Brrrr!
So, based on this wild solubility behavior, methanol seems like the better solvent for recrystallization. Why? Because it can dissolve more of our compound both at high and low temperatures, making it easier to dissolve, filter, and then crystallize the compound back out. Water, on the other hand, is a little more finicky, being a party animal at high temperatures but a total freeze-bot at low temperatures.
That's the lowdown on solubility, my friend. Now go forth and recrystallize with a big smile on your face!
To determine which solvent would be better for recrystallization of the compound, we need to consider the solubility of the compound in each solvent at room temperature. Recrystallization is a technique used to purify a solid compound by dissolving it in a hot solvent and then allowing it to slowly cool down, causing the compound to crystallize out.
In this case, we have two solvents: methanol and water. Let's compare the solubility of the compound in both solvents at room temperature.
The solubility of the compound in boiling methanol is 59g per 100mL, indicating that it is highly soluble in hot methanol. However, in cold methanol, the solubility decreases to 30g per 100mL, indicating that it is less soluble at lower temperatures.
Similarly, in water, the solubility of the compound is 7.2g per 100mL at 95°C and 0.22g per 100mL at 2°C. This indicates that the solubility of the compound in water decreases significantly as the temperature decreases.
Based on these solubility values, we can conclude that methanol would be a better solvent for recrystallization of the compound. This is because the compound is more soluble in methanol at room temperature (30g per 100mL) compared to its solubility in water (0.22g per 100mL). Higher solubility in the recrystallization solvent will allow more compound to dissolve during heating, ensuring a higher yield of the purified solid compound upon subsequent cooling.
In summary, the higher solubility of the compound in methanol compared to water at room temperature makes methanol a better solvent for the recrystallization process to purify the compound.