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Percentage yield HELP!!!

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waiting to use percentage yield now like the title suggests...!

The coefficient never tells you how many moles are actually there, but rather the RATIO in which it reacts with other reactants.

2x + 5y ---> 3z + 4w

This means that every 2 moles of x react with 5 moles of y producing 3 moles of z and 4 moles of w

It doesn't tell you how many moles of each substance you actually have...just the RATIO in which they react...very important you don't get confused...

Ohh okk thanks once again
What board r u doing for science???

Reply 21

Dylann

Original post by Fallen99

Ohh okk thanks once again
What board r u doing for science???

I'm an A2 student doing AQA :smile:

Reply 22

Fallen99

Original post by Dylann

I'm an A2 student doing AQA :smile:

Ohh that is why u r soo good at chemistry just one more question
You said we can add the masses together but can we workout the moles for each compound and add them together??

Reply 23

Dylann

Original post by Fallen99

Ohh that is why u r soo good at chemistry just one more question
You said we can add the masses together but can we workout the moles for each compound and add them together??

I didn't realise the equation wasn't balanced :wink:

not that good haha!

You shouldn't add the masses together...you should work out the moles of each reactant individually and see which is in excess

Reply 24

Fallen99

Original post by Dylann

I didn't realise the equation wasn't balanced :wink:

not that good haha!

You shouldn't add the masses together...you should work out the moles of each reactant individually and see which is in excess

I didn't realize that too.
I get that we can work out the moles of reactants individually but what do u mean by which is in excess??

Reply 25

Asad_2015

its just outcome yield divided by actual yield and time by 100. It's the easiest calculation i think in c2. gl.

Reply 26

Dylann

Original post by Fallen99

I didn't realize that too.
I get that we can work out the moles of reactants individually but what do u mean by which is in excess??

If there are 2 moles of X and 3 moles of Y and they react in a 1:1 ratio then Y is in excess...i.e. when all of X is used up there is still some Y left over.

Reply 27

Fallen99

Original post by Dylann

If there are 2 moles of X and 3 moles of Y and they react in a 1:1 ratio then Y is in excess...i.e. when all of X is used up there is still some Y left over.

Thanks a lot do u mind if I look out for u on tsr if I need help in chemistry in the future??

Reply 28

Dylann

Original post by Fallen99

Thanks a lot do u mind if I look out for u on tsr if I need help in chemistry in the future??

Yeah just PM me

Reply 29

Fallen99

Original post by Dylann

Yeah just PM me

Thanks

Posted from TSR Mobile

Reply 30

Wolfram Alpha

Original post by Dylann

mol=Mass in grams/Mr

Mr = Relative molecular mass (sum of all relative atomic masses) i.e. Mr of CuCl2 = 63.5 + (2x35.5) =134.5

Quite a fundamental formula that you should certainly know!

Thank you!!!

Reply 31

Wolfram Alpha

Original post by Fallen99

Sorry but the method is right I just did it again with the balanced equation and the answer is
Use this formula= mass= moles*relative formula mass
So first work out the relative formula for each of them. Lets start with CuCl2
Cu= 63.5
Cl= 35.5*2= 71
Than it is 2NaNO3
Na= 23*2=46
Nitrogen= 14
Oxygen =16*3 = 48
Add the relative formula mass of CuCl2+NaNO3 together= 242.5
And you have the total mass of 15+20=35 grams
Use this to work out moles which is mass/ relative formula mass
Moles= 35/242.5= 0.1443298962
Now work out the relative mass for 2NaCl
Na= 23*2= 46
Cl= 35.5*2= 71
Add them together= 117
For this you have to find mass which is moles* relative mass
0.1443298962*117= 13.37659786
So 13.37659786 Nacl can be formed

Thank you very much!!! Something that I actually understand.