[jonj1_12]

Have got a test in a couple of weeks on molecular bioscience and finding this question hard.. asked the lecturer for answer but he hasn't done the answers himself yet and wont let me know as he doesnt want the class to have any answers yet... Would be really grateful if somebody could answer the question and explain how...

Consider the following balanced reaction:
4NH3 + 5O2 --> 4NO +6H2O

* how many grams of NH3 are necessary to react with 46g of O2?
* how many mols of NO will be formed?
*how many molecules of H2O will be formed?

Thank you if you can answer it

[Arkcon]

The first step is to be able to convert grams of O₂ into moles of O₂.  Can you do this?  Do you know, from somewhere, the mass of an oxygen atom.  You may have come across it ... periodically.

[jonj1_12]

Yeah.. i did think this, i get 0.28 mols.. so then do i have to do the ratio of that to get the NH3 and then convert the mols with the molar mass to get the grams?
Thanks

[Borek]

Yeah.. i did think this, i get 0.28 mols..

0.28 moles doesn't look correct to me for 46 g of oxygen, please show how you got it.

so then do i have to do the ratio of that to get the NH3 and then convert the mols with the molar mass to get the grams?

Sounds like a viable approach.

[jonj1_12]

Yeah i was multiplying it by the coefficent as well which i just worked out i shouldnt be doing so..
= 46/32 = 1.4375 mols..
Do i now have to mulitply this by the difference between the coefficients and then use that mols and multiply by the molar mass for NH3?
 

[Borek]

46/32 = 1.4375 mols

OK

Do i now have to mulitply this by the difference between the coefficients

Ratio of the coefficients, not the difference.

[jonj1_12]

Yeah that's what i meant..

[MathisFun]

Hello jonj1_12,

In answering your inquiry into "how many grams of NH₃ are necessary to react with 46g of O₂?," I'll provide an example equation. Hopefully, you can learn from it and apply it to future equations.

N₂ + 3H₂  2NH₃

How many grams of N₂ are necessary to produce 7.50 g of NH₃?

The coefficients in the equation refer to the relative number of moles, not grams. I'll refer to the Periodic Table of Elements to find the mass of N₂ and NH₃,

N - 2 - 14.00674 = 28.01348 g

N - 1 - 14.00674 = 14.00674 g
H - 3 -   1.00794 =   3.02382 g
                             17.03056 g

Looking at the above equation, we see that 2 mol NH₃ are produced from 1 mol of N₂, thus the conversion factor, 2 mol NH₃ = 1 mol N₂.

(7.50 g NH₃)(1 mol NH₃/17.0 g NH₃)(1 mol N₂/2 mol NH₃)(28.0 g N₂/1 mol N₂) = 6.18 g N₂

Note: I'm not sure what method your class adopts, concerning significant figures. Adjust accordingly.

For your other 2 inquiries, based on what I have learned, thus far, I would require more info. I would love to learn how to solve for it though, given the data on hand.