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Chemistry Forums for Students => High School Chemistry Forum => Topic started by: TheSniteBros on February 24, 2018, 08:30:54 PM

Title: Stoichiometry+PV=nRT
Post by: TheSniteBros on February 24, 2018, 08:30:54 PM
I have a HW question and was out sick during the lesson. Could anyone explain the following to me.

Suppose ammonia (NH3) is made by the haber process. If 10.0 kg of N2 gas is reacted with excess H2 gas at 550. C and 250 atm, what volume of ammonia is produced?

The balanced equation is N2 + 3 H2 = 2 NH3

Please get back ASAP.
Thanks.
Title: Re: Stoichiometry+PV=nRT
Post by: Arkcon on February 24, 2018, 09:41:29 PM
Quote
Suppose ammonia (NH3) is made by the haber process. If 10.0 kg of N2 gas is reacted with excess H2 gas at 550. C and 250 atm, what volume of ammonia is produced?

The balanced equation is N2 + 3 H2 = 2 NH3

Good.  You have a balanced equation.  You have one set of units for reactants, and a different set of units for products.  You have to convert.  Fortunately, you have a formula, PV=nRT, for that.

Quote from: TheSniteBros on February 24, 2018, 08:30:54 PM
I have a HW question and was out sick during the lesson. Could anyone explain the following to me.

Quote
Please get back ASAP.
Thanks.

Kindly review our Forum Rules{click} (http://www.chemicalforums.com/index.php?topic=65859.0).  You already accepted the rules when you signed up for our forum, and you have to follow them, whether you agree with them or not, or even if you're unaware of them.
Title: Re: Stoichiometry+PV=nRT
Post by: TheSniteBros on February 25, 2018, 12:21:14 PM
Ya but could you please explain HOW to do the problem or possibly even do it so I can understand how to do the rest of my HW. Thanks.
Title: Re: Stoichiometry+PV=nRT
Post by: Borek on February 25, 2018, 12:40:14 PM
How do you approach EVERY stoichiometry problem?
Title: Re: Stoichiometry+PV=nRT
Post by: TheSniteBros on February 25, 2018, 01:36:08 PM
Well what I did was i converted 10 kg to g and then g to mols. Then I plugged in all the variables in PV=nRT. I end up with 250V= 169191.63 and then I divide both sides by 250. Then i got 676.8 L of N2 gas and from there I have no idea what to do.
Title: Re: Stoichiometry+PV=nRT
Post by: chenbeier on February 25, 2018, 02:24:49 PM
You have to approach the stoechiometry. The moles what you calculated is not ammonia.
Title: Re: Stoichiometry+PV=nRT
Post by: Arkcon on February 25, 2018, 02:43:14 PM
Quote from: TheSniteBros on February 25, 2018, 01:36:08 PM
Then i got 676.8 L of N2 gas and from there I have no idea what to do.

Adding to what chenbeier: said, you computed liters of N2 gas.  What are the units of the relationship between N2 gas and ammonia product?  There are units in the "equation" that is a balanced chemical reaction, they're just hidden.
Title: Re: Stoichiometry+PV=nRT
Post by: TheSniteBros on February 25, 2018, 03:26:37 PM
So i should do a mole to mole ratio so I find the moles of NH3? This would mean that I would just be doubled since its a 2 mol nh3/ 1 mol  n2. That means the answer is 1353.64 L NH3?
Title: Re: Stoichiometry+PV=nRT
Post by: Borek on February 25, 2018, 03:39:50 PM
Logic looks more or less correct, but the final result doesn't.

What was the number of moles of N2 that you found?

What value have you used for R?
Title: Re: Stoichiometry+PV=nRT
Post by: Enthalpy on February 27, 2018, 08:49:08 AM
This homework question probably wants you to use the perfect gas law, so do it like that.

But keep in mind that at 250atm, a gas does not follow that law. Its density is too near to the liquid's one, so the volume of the molecules makes an important correction, like 5% here.

But if the question was "what volume at standard pressure and temperature", then dry ammonia follows closely the perfect gas law.