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Chemistry Forums for Students => High School Chemistry Forum => Topic started by: amoralyn12 on February 23, 2010, 10:58:59 PM

Title: Gases, Intermolecular Forces, and Solutions
Post by: amoralyn12 on February 23, 2010, 10:58:59 PM

Hi, I've been working on this free response question, but I'm unsure if I'm doing it right. I'll post the first parts that I have done first, and continue editing when I have gone further into the question. Please tell me if I am doing things correctly, or if not, tell me what I am doing wrong and how to fix it. Thanks.

Here's the question: A mixture of 0.300 mol each of hydrogen gas, oxygen gas, and liquid water are present in a 20.00 liter container at 25 degrees Celsius. The equilibrium vapor pressure of water at 25 degrees Celsius is 23.76 torr.

(a) Calculate the total pressure inside the flask.

I used the ideal gas law to find the partial pressure of the gases, PV=nRT and modified it to become P=(nRT)/V
n= 0.600 mol of gases
R= 0.08206 L atm / mol K
T= 298 K
V= 20.00 L

(0.600)(0.08206)(298) / 20.00 = 0.73 atm

Then I added the vapor pressure of water,
P= (23.76 torr)(1 atm/760 torr)= 0.3 atm
0.73 atm+0.3 atm= 0.76 atm

(b) Using principles of kinetic molecular theory, explain which gas has the
 :rarrow: highest average kinetic energy
The kinetic molecular theory states that at any given temperature, the molecules of all gases have the same average kinetic energy.
 :rarrow: highest average velocity of molecules
For this reason, the gas with the smallest mass will have the highest average velocity of molecules (hydrogen gas).
 :rarrow: highest density
The oxygen gas will have the highest density because it has a larger atomic mass than hydrogen, meaning that at equal moles the oxygen will have more oxygen atoms.

I'm really not sure of this next part...

(c) The mixture is sparked, a reaction ensues consuming one of the reactants entirely, and the resulting mixture is allowed to come to equilibrium at 80 degrees Celsius.
 :rarrow: Write and balance a chemical equation to describe the reaction.
I'm have a lot of problems with chemical equations. How can I predict the products?
H_2(g)+O_2(g)+H₂O_(l)  :rarrow: 2H₂O_(g)+H⁺
 :rarrow: Which is the limiting reactant? Explain.
I would guess that oxygen is the limiting reactant. However, it is only a guess and I have no explanation.
 :rarrow: Calculate the total pressure in the flask after the reaction is complete. The water vapor pressure at 80 degrees Celsius is 355 torr.
Working...

Title: Re: Gases, Intermolecular Forces, and Solutions
Post by: Borek on February 24, 2010, 03:13:22 AM

Water that is initially present doesn't take part in the reaction. Try just reaction between hydrogen and oxygen.

Title: Re: Gases, Intermolecular Forces, and Solutions
Post by: kimyacı on February 28, 2010, 02:00:36 PM

 İn fact,even at the begining this reaction begin, but very very slow.Because of its very much activation energy, Light or a metal catalyst is needed to occur reaction fast.