Gen Chem -- EK

This forum made possible through the generous support of SDN members, donors, and sponsors. Thank you.

Just Joshin

New Member
10+ Year Member
5+ Year Member
15+ Year Member
Joined
Aug 13, 2006
Messages
695
Reaction score
3
This is probably real simple and I'm makng it harder than it is. If someone can explain it to me like I'm 2, I'd appreciate it because I can't wrap my mind around the explanation in the book:

4NH3 (g) + 7O2 (g) ---> 4NO2 (g) + 6H2O (l)

If 8 moles of NH3 are reacted with 14 moles of O2 in a rigid container with an initial pressure of 11 atm, what is the partial pressure of NO2 in the container when the reaction runs to completion? (assume constant temp)

(A) 4 atm
(B) 6 atm
(C) 11 atm
(D) 12 atm

The answer is A, but I don't get it.

Members don't see this ad.
 
This is probably real simple and I'm makng it harder than it is. If someone can explain it to me like I'm 2, I'd appreciate it because I can't wrap my mind around the explanation in the book:

4NH3 (g) + 7O2 (g) ---> 4NO2 (g) + 6H2O (l)

If 8 moles of NH3 are reacted with 14 moles of O2 in a rigid container with an initial pressure of 11 atm, what is the partial pressure of NO2 in the container when the reaction runs to completion? (assume constant temp)

(A) 4 atm
(B) 6 atm
(C) 11 atm
(D) 12 atm

The answer is A, but I don't get it.

This problem is testing Avagadro's Principle, where n1/v1=n2/v2. You are given the initial number of moles, the final number of moles, and the the initial pressure...
 
I'm sorry to be dense, but what? I don't understand how you can do it with n1/v1=n2/v2
 
Hmm... Yea the wording is really bad... It is saying that the inital pressure is 11atm After 22 mols of gas has been added.

8NH3 (g) + 14O2 (g) ---> 8NO2 (g) + 12H2O (l)

Partial pressure of NO2 == Ptotal because the rxn goes to completion and liquids don't exert a partial pressure.

Since PV=nRT and V,R,and T are constants... P/n = constant.

P1/n1 = P2/n2

11atm/22moles = P2/8moles

P2 = 4atm
 
Members don't see this ad :)
you can do it quicker. If you realize there are 22 mols of gas in a container at a pressure of 11 atm, how much pressure would 8 mols of gas be in the same container? its a 2:1 relationship.
 
Top