How do I set up this GC problem?

[JustwantDDS]

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My mind is failing me right now...

how do i set this up
If the rate of disappearance of H2 is 6M/min, then what is the rate of appearance of NH3?
N2(g) + 3H2(g) → 2NH3(g)


Answer key says [NH3]/t = 6M/min(2 mol NH3/3mol H2)= 4M/min

uhhh i just dont get it.

 

[herkulease]

this is a basic stoichiometry problem

you can completely ignore the time portion of the question.

And rephrase the question as if you have 6 moles of H2 how many NH3 will you produce.

6 moles H2 (2 mols NH3/3 moles H2) = 4 moles of NH3 produced.

the time thing is just to mess with you.

 

[JustwantDDS]

this is a basic stoichiometry problem

you can completely ignore the time portion of the question.

And rephrase the question as if you have 6 moles of H2 how many NH3 will you produce.

6 moles H2 (2 mols NH3/3 moles H2) = 4 moles of NH3 produced.

the time thing is just to mess with you.

soooo for future problems, you can just throw in the /min?

cuz the answer is 4M/min...
😕

 

[dentalfanatic]

Well since the units don't change you can simply substitute moles for M/min... Just like if you have 15% of something and you use 15 grams...does that make sense?

 

[needzmoar]

soooo for future problems, you can just throw in the /min?

cuz the answer is 4M/min...
😕

you're dealing with rate so the units of your answer must include a unit of time.

 

[herkulease]

soooo for future problems, you can just throw in the /min?

cuz the answer is 4M/min...
😕

well you can throw in /min as the answer I assume are also in /min

but lets say they don't and its just a regular problem and want you to determine rate of appears of NH3 per seconds

what I do with these problems is do dimensional analysis. it can be long but you are guaranteed the answer as long as you use the correct relationships so that you can cancel out everything leaving the desired answer.

I usually write down down what I am given and what they want.

6 Moles of H2/min

leave blank space

then

moles of NH3 / Second

from the balance equation we get the relationship of 2 mols NH3/3 moles H2
(this allows us cancels out that moles of H2 leaving use with moles of NH3 in the numerator)

and we have the relationship of 1 min / 60 seconds, this cancels out minute in the denominator and allows us to now have seconds.

once you cancel you can multiply thru use be left with the units Mols NH3/second

I'm not gonna work out the answer but you should get the idea. It might be longer but will work with anything they throw at you. they can ask the question backwards, different units whatever.

 

[DrRoyal Pains]

Its all in the ratio's mah man