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Topic: reactions with gases?  (Read 15043 times)

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Offline Shea

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reactions with gases?
« on: August 17, 2006, 04:36:42 PM »
What volume of O2 at 298K and 2 atm is required to react completely with 2L of Methane at the same temperature and pressure?

Can someone just tell me the first step to this?
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Offline Will

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Re: reactions with gases?
« Reply #1 on: August 17, 2006, 05:24:27 PM »
The first step is writing a balanced equation for the complete combustion of methane.
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Offline Shea

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Re: reactions with gases?
« Reply #2 on: August 17, 2006, 05:59:44 PM »
How do I know what the reaction produces?
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Offline Will

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Re: reactions with gases?
« Reply #3 on: August 17, 2006, 06:02:07 PM »
Quote from: Shea on August 17, 2006, 05:59:44 PM
How do I know what the reaction produces?

CO2 and H2O. Those are always (AFAIK) the products of complete combustion of hydrocarbons.
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Offline Shea

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Re: reactions with gases?
« Reply #4 on: August 17, 2006, 06:07:37 PM »
2O2 + CH4 -> CO2 + 2H2O

I have the equation.  Now do I use PV=nRT or something to find how many moles and stuff there are in the gas?
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Offline Will

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Re: reactions with gases?
« Reply #5 on: August 17, 2006, 06:24:04 PM »
Think about it... double moles of oxygen required... double volume... maybe?
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Offline Shea

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Re: reactions with gases?
« Reply #6 on: August 17, 2006, 06:35:07 PM »
2 liters of methane would need 4 liters of O2.

Is that it???

This question looked a lot harder before...

 :-\
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Offline Will

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Re: reactions with gases?
« Reply #7 on: August 17, 2006, 07:00:14 PM »
Quote from: Shea on August 17, 2006, 06:35:07 PM
2 liters of methane would need 4 liters of O2.

Is that it???

I sure hope so. My brain is not functioning at its best today from the excitement of just receiving my A-Level results and starting uni in two weeks.
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Offline Mitch

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Re: reactions with gases?
« Reply #8 on: August 17, 2006, 07:08:12 PM »
Quote from: Shea on August 17, 2006, 06:35:07 PM
2 liters of methane would need 4 liters of O2.

Is that it???

This question looked a lot harder before...

 :-\

I don't think thats correct. But, I haven't done the math to prove it. Why don't you solve for the number of moles of methane you have in your reaction by using PV=nRT
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Offline Yggdrasil

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Re: reactions with gases?
« Reply #9 on: August 17, 2006, 07:12:18 PM »
Avogadro's hypothesis states that the number of moles of a gas is directly proportional to its volume at a specific temperature and pressure.  So, it's unecessary to convert to moles when using ideal gasses.  A 2:1 ratio of moles of oxygen gas to methane is equal to a 2:1 ratio of liters of oxygen gas to methane, so Shea's answer is correct.
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Offline Mitch

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Re: reactions with gases?
« Reply #10 on: August 17, 2006, 07:14:11 PM »
okay
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Offline Shea

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Re: reactions with gases?
« Reply #11 on: August 17, 2006, 07:18:25 PM »
2atm x 2Liters / .082 x 298 = .164 moles of Methane.

And that means that there would need to be .328 moles of O2.

I think it IS 4L

V = (nrt)/p

0.328 x 0.082 x 298 / 2 = 4.0075 L

Huh, it looked a lot more difficult before.
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Offline Shea

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Re: reactions with gases?
« Reply #12 on: August 17, 2006, 07:37:06 PM »
Thanks, by the way, for telling me of avogadro's hypothesis.  That clears up some confusion on some other problems I have.
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Offline Shea

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Re: reactions with gases?
« Reply #13 on: August 18, 2006, 05:56:58 PM »
What about this one?

50 mL of 2M NaBr is reacted with excess Cl2. The Br2 gas given off is collected. What volume would the gas occupy at 298 K and 1 atm?

I thought this one was another for avogadros hypothesis, but I was wrong.
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Offline Borek

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Re: reactions with gases?
« Reply #14 on: August 18, 2006, 06:07:43 PM »
What is Br2 boiling point?

Regardless of the answer start with the balanced reaction equation.
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