IdahoDoc

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If someone could please explain how they are setting up this problem that would be great. I can do the math out and get the correct answer i just don't see how they set it up. thanks
 

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MaskItOrCasket

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Qhow many moles of water are formed from 100g H2 and 100g O2 asssuming the reaction goes to completion?

1) write out formula: H2+.5O2-> H2O
2) find limiting reactant- its oxygen bc it has a heavier molar mass compared to hydrogen therefore there are less moles of O2 in 100g than moles of H2. dont bother doing the calculation: save time
3) set up dimensional anaylsis:
)
100 g O2 x (1 mol O2/ 32g O2) x ( 1 mol H2O/ .5 mol O2) = 100/(32x.5) or 2(100/32) which is choice C
 

IdahoDoc

10+ Year Member
7+ Year Member
Aug 26, 2007
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  1. Dental Student
Qhow many moles of water are formed from 100g H2 and 100g O2 asssuming the reaction goes to completion?

1) write out formula: H2+.5O2-> H2O
2) find limiting reactant- its oxygen bc it has a heavier molar mass compared to hydrogen therefore there are less moles of O2 in 100g than moles of H2. dont bother doing the calculation: save time
3) set up dimensional anaylsis:
)
100 g O2 x (1 mol O2/ 32g O2) x ( 1 mol H2O/ .5 mol O2) = 100/(32x.5) or 2(100/32) which is choice C

Thanks Panther 85, I got it now I was skipping this part (1 mol H2O/ .5 mol O2).
 
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