Tuesday
May 5, 2015

Homework Help: science(chem)

Posted by ~christina~ on Monday, September 3, 2007 at 12:12pm.

I'm confused as to what to do for the calculations for my lab.

Lab: Semimicroscale crystalization-erylenmyeyerflask and Hirsch Funnel

Weigh 0.30g of impure sulfanilamide and then transfer to a 10ml Erlenmeyer flask. To a second Erlenmeyer flask add about 6ml of 95% Ethyl alcohol and a boiling stone.

summary of procedures:
Add enough hot solvent to just cover crystals and then heat untill boiling and swirl to dissolve crystals.
To crystalize allow flask to cool slowly. Use ice bath to induce crystalization. Filter using Hirsch funnel. Rinse with 1ml portion of ice cold ethanol. Transfer crystals to a preweighed watch glass.

A pre lab Q..
Calculate how much 95% ethanol will be required to dissolve 0.3g of sulfanilamide at 78%.

How would I find this?? I haven't any clue and there are no sample calculations in my lab book coincidentally.

How would I then find the percent yield?
~ for this wouldn't I go and divide
the (amound left)/(original ammount)*100= percent yield?

I seriously need help on these calculations (they really need to include sample calculations in this book)

Thanks

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