Competition - post a photo you've taken of nature >>

Yield percentage

Question 4 is the one I need help with the book says the answer is 21% (21.2%) but I just don't know how to get that answer. I've been fine throughout the questions until this point and my text box doesn't actually give an worked example of this type of question.... It's 2:30am and I can't sleep because it's annoying me, buzzing around my head got the past 4 hours, I'm defeated by this one...: please can someone help me.... It would be greatly appreciated

Reply 1

WinterDucky

Not sure where the problem lies since it's a very simple question.

Moles of N2: 0.25 therefore moles of NH3 is 0.5

0.5 * 17 = 8.5g

1.8/8.5= 0.21

Reply 2

Dora amos

Original post by WinterDucky

Not sure where the problem lies since it's a very simple question.

Moles of N2: 0.25 therefore moles of NH3 is 0.5

0.5 * 17 = 8.5g

1.8/8.5= 0.21

I'm sorry I haven't come across miles yet.... Maybe I missed that class... It comes like 4 pages later in the chapter

I know that N+H all together = 17 I was under the impression we divided for this.... Maybe my teacher didn't explain it correctly
Thank you

Reply 3

Dora amos

Original post by vickie89uk

Original post by WinterDucky

Not sure where the problem lies since it's a very simple question.

Moles of N2: 0.25 therefore moles of NH3 is 0.5

0.5 * 17 = 8.5g

1.8/8.5= 0.21

Im Sorry but don't understand how moles of N are 0.25 1 mole of nitrogen is 14g I get the rest of it i think I just don't understand how nitrogen is now 0.25

(edited 8 years ago)

Reply 4

WinterDucky

Original post by vickie89uk

Im Sorry but don't understand how moles of N are 0.25 1 mole of nitrogen is 14g I get the rest of it i think I just don't understand how nitrogen is now 0.25

Nitrogen is diatomic, as in it always comes in pairs. Therefore it's molar mass is 28 so divide the #of grams by 28 to get the moles.

Reply 5

Dora amos

Original post by WinterDucky

Nitrogen is diatomic, as in it always comes in pairs. Therefore it's molar mass is 28 so divide the #of grams by 28 to get the moles.

I'm sorry I'm clearly thick but I don't get it... If they come in pairs they are 28 so now what is the grand I divide by to get 0.25

Sorry I thought 17 then 14 then 28/28 isn't right I'm lost

Reply 6

Dora amos

Original post by WinterDucky

Nitrogen is diatomic, as in it always comes in pairs. Therefore it's molar mass is 28 so divide the #of grams by 28 to get the moles.

Ha 7 I got it how stupid was that 7g of nitrogen what a wally thanks for your help

Reply 7

WinterDucky

Original post by vickie89uk

Ha 7 I got it how stupid was that 7g of nitrogen what a wally thanks for your help

No problem :smile:

Reply 8

Dora amos

Original post by WinterDucky

No problem :smile:

Thank you so much it's so simple when someone explains it....

Haha I will remember that the hours I racked my brain I was dividing 14/7 plank
So I did 7/14 to make it make sense to me = 0.5
N=14 3xH = 3 14+3=17.
0.5x17= 8.5
1.8g we made / 8.5 = 0.2110
0.211x100 = 21.1%Thank youSo to clarify without thinking of nitrogen as diatomic all for now when faced with these questions you divide the grams used/reacted (7g) by the atomic mass (14) 0.5... then add you atomic mass together in the full chemical reaction so NH3 (14+3=17) multiply them together 0.5x17 = 8.5 and what we collected is divided by 8.5 (1.8/8.5=0.211) then 0.211x100 = 21.1%Is that right