Kaplan blue page 671, #49 Gen CHEM

I think your thinking is on the right path. But what was your answer?72% or 57.6%. I am thinking.... maybe you should do this( I am not sure i am looking it up!)

([given]gof compound)(mole/gcompound)= moles of compound

(molcomp)(moleO/molcomp)(gO/1mol)=gO

massO/Total*100%=?

g/250g*100= % or g/200g*100%= %. Let me know. this is either really easy or tricky
Kaplan doesn't explain this well I originally would think to do it just massofO2/total mass but the 200g is throwing me.

 

200g sample * 1mole sample/total sample weight * 9 mole O/ 1 mole sample * 1 mole O/ 16g O = g oxygen/total sample weight * 100 = % O

it says 200g sample because it is using specific amount of sample. think about what if you use 200g water instead of 2000g water what will happen? in the 2000g water the oxygen % will will a lot higher than the Oxygen level in the 200g sample.

 

Good I am glad to know I was on the right track!!!!!!!!!!!!!!!!

 

yes,
i just looked in the kaplan blue book and it says that we don't have to worry about the 200g or any sample size, so the size of the sample doesn't affect the oxygen compoistion percentage.