MOST ASWOME LESSON ON PERCENTAGE WHICH WE DIDN"T LEARN IN GRADE 2!!!!! FUN FUN FUN FUN FUN!!

life is like a sign sigh.

Yay after the long break we finally start learning again.. fun…..

Don’t have much time so Less random stuff sorry~ and of course we all still remember the super fun and exciting lab right?

Okay~ we are doing Percent Yield and Percent Purity

So what is Percent Yield and Percent Purity Percent yield is found by dividing the actual mass of product formed by the mass of the product expected hmm what does this mean? It means that Percent yield is how much stuff will be produced when 2 chemicals are reacted together so what percentage of thing is actually formed.

Percent Purity on the other hand is the percent of a specified compound or element in an impure sample. So out of the big chunk of rocks how much of it is actually useful? Only the useful stuff reacts.

Okie examples…

3Mg(OH)2 + 2H3PO4 H Mg3(PO4)2 + 6H2O

Q1 Calculate the mass of Mg3(PO4)2 that will be formed (100% yield) from the

reaction of 15.0 g of 92.5% Mg(OH)2 with an excess of H3PO4.

13.875g Mg(OH)2 * 1 mole Mg(OH)2/ 1 mole Mg(OH)2 * 1 mole Mg3(PO4) 2/ 3 moles Mg(OH)2 * 262.9 g Mg3(PO4)2/ 1 mole Mg3(PO4)2 = 20.9 g Mg3(PO4)2   (typing that took years)

Q2 Calculate the mass of 88.5% Mg(OH)2 needed to make 127 g of Mg3(PO4)2, assuming a

100% yield.

Gold ore

127 g Mg3(PO4)2 x1 mole Mg3(PO4)2 / 262.9 g Mg3(PO4)2 *  3 moles Mg(OH)2 / 1 mole Mg3(PO4)2  *  58.3 g Mg(OH)2 / 1 mole Mg(OH)2   = 84.49 g Mg(OH)2.

Okay Percent Yield Question

CaC03 ---> Ca0 + C02
If 50kg of Calcium carbonate is used, and 21kg of calcium oxide is made, what is the percentage yield of the reaction?

The reaction is OMG I don’t know how to do this…  Jokes…

50 kg CaCO3 x (1000 g CaCO3 / 1 kg CaCO3) x (1 mole CaCO3/ 100.09 g CaCO3) x (1 mole CaO / 1 mole CaCO3) / (56.08 g CaO / 1 mole CaO) x (1 kg CaO/ 1000 g CaO) = 28.015 kg CaO

Hahahah you see how the Kg part screwed everyone over? XD

21 kg / 28 kg = 75% yield

a chinese dude teaching win!

http://misterguch.brinkster.net/pra_equationworksheets.html

god level site for chemistry!