[Chimery]

Hey everyone. Unfortunatly my first post is going to be a specific problem I have, but I am planning to stick around because I like science personally, with particular interests in genetic engineering.    

We're doing stoich/gas review and I have a test tomorow morning.  I tried figuring it out but I'm stumped, so I need your help.  I'll show you what I did and where I got stuck.


Problem:  
You're given the following unbalanced equation (occuring at STP)...
C₂H₂ + O₂  --->  CO₂ + H₂

which I balanced as...
2C₂H₂ + 2O₂  --->  2CO₂ + 2H₂

Calculate the number of grams of oxygen required to react with 25L of C₂H₂ at 0.989 atm and 23^oC


I started by converting 25L into its volume at STP, which was 22.932L

I did this so I could convert my 22.932L of C₂H₂ into grams, which was 25.593g.

because the ratio of O₂ to C₂H₂ is 2:2, so it's 25.593 of O₂  (still at STP)

Now this is where I run into trouble.  I need to convert that mass of O₂ into non-STP to solve the problem, namely 0.989 atm.  

To do that conversion, I need those O₂ grams in litres, which is fine...  But once I finally convert my litres of O₂ into non-STP... I can't switch my litres back into grams (with  V=formula mass/22.4L), because I'm not operating under STP anymore!






I just don't know what to do.

[Black Mage]

Double check your balanced equation.

[Chimery]

Double check your balanced equation.

oops, thanks.  The problem still stands though.

I'm wondering now if I misread the question.  Does the question imply that the 25L of oxygen is at STP or at 0.989 atm?

[Black Mage]

Double check your balanced equation.

oops, thanks.  The problem still stands though.

I'm wondering now if I misread the question.  Does the question imply that the 25L of oxygen is at STP or at 0.989 atm?

0.986 atm is STP.

[Chimery]

Double check your balanced equation.

oops, thanks.  The problem still stands though.

I'm wondering now if I misread the question.  Does the question imply that the 25L of oxygen is at STP or at 0.989 atm?

0.986 atm is STP.

No... 1 atm is STP. 


Besides, it wants it in 0.989 atm as well as 30^oC. 

[Black Mage]

Double check your balanced equation.

oops, thanks.  The problem still stands though.

I'm wondering now if I misread the question.  Does the question imply that the 25L of oxygen is at STP or at 0.989 atm?

0.986 atm is STP.

No... 1 atm is STP. 


Besides, it wants it in 0.989 atm as well as 30^oC. 

http://en.wikipedia.org/wiki/Standard_conditions_for_temperature_and_pressure

[Chimery]

Double check your balanced equation.

oops, thanks.  The problem still stands though.

I'm wondering now if I misread the question.  Does the question imply that the 25L of oxygen is at STP or at 0.989 atm?

0.986 atm is STP.

No... 1 atm is STP. 


Besides, it wants it in 0.989 atm as well as 30^oC. 

http://en.wikipedia.org/wiki/Standard_conditions_for_temperature_and_pressure

"...while NIST's version is absolute pressure of 101.325 kPa (14.696 psi, 1 atm)."

Anyways... as the question obviously states, it wants it in 30C for temp as well.

[Chimery]

I think I got stuck because I misinterpreted the question.  If the volume is originally in STP, there won't be a problem.  

thanks anyways.

STP= 1 where I come from, and if you're not with us... you're against us