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Topic: Stoichiometry Problem  (Read 36358 times)

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Offline JonathanEyoon

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Stoichiometry Problem
« on: February 16, 2008, 05:53:46 PM »
Water can be formed from the stoichiometric reaction of hydrogen with oxygen:



A complete reaction of 5.0 g of O2 with excess hydrogen produces how many grams of H2O?



I'm having a worst time with this one than the other one I had.  I don't even know where to start off  ??? Any help is much appreciated.

Offline ARGOS++

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Re: Stoichiometry Problem
« Reply #1 on: February 16, 2008, 06:19:03 PM »
Dear JonathanEyoon;

Every Stoichiometry Problem starts with the same Steps:

  • A.)   Build the “Reaction Equation” for your Problem.
  • B.)   Balance1) the “Reaction Equation” with the required Indices, giving you the Stoichiometry. 
  • C.)   Translate the known masses for the “Reaction Equation” into the corresponding number of Moles.
  • D.)   Maybe you have to find the limiting Reagent.
  • E.)   Calculate from C.) and D.) the still missing masses using the number of Moles from the “Reaction Equation”. 
  • F.)   Identify your Result.

1) For “How to Balance a Chemical Reaction” you may read on: "Balancing Chemical Equations
2) How the ‘whole’ Diagram/Scheme for the second Example must look you can see on the:  "Replay #36 and #37”.

I hope this small Recipe may be of help to you to solve your Stoichiometry.

Good Luck!
                    ARGOS++

« Last Edit: April 02, 2008, 05:19:47 AM by ARGOS++ »

Offline JonathanEyoon

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Re: Stoichiometry Problem
« Reply #2 on: February 16, 2008, 06:24:14 PM »
I don't even know how to set up the problem  ??? That's why i'm having such a hard time with this stuff.
« Last Edit: July 19, 2015, 05:15:36 PM by Arkcon »

Offline Sev

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Re: Stoichiometry Problem
« Reply #3 on: February 16, 2008, 06:32:42 PM »
Start with rxn eqn (as Argos++ mentioned)

Offline JonathanEyoon

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Re: Stoichiometry Problem
« Reply #4 on: February 16, 2008, 06:36:37 PM »
ok. How do I start that?

Offline ARGOS++

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Re: Stoichiometry Problem
« Reply #5 on: February 16, 2008, 06:40:18 PM »
Dear JonathanEyoon;

Let’s try to do A.) and B.) together:

A.)         Reaction:        O2   +     H2    ----->    H2O.
B.)         Balancing:     1O2   +   2H2    ----->  2H2O. 
C.)         Are you able to find all required Molecular Weights (MW), and translate your 5.0 g O2 into the Number of Moles?

Will this be enough for the Start?

Good Luck!
                    ARGOS++


Offline JonathanEyoon

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Re: Stoichiometry Problem
« Reply #6 on: February 16, 2008, 06:57:36 PM »
yea I know how to find MW and convert to mols.  What do I do from there?

Offline Sev

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Re: Stoichiometry Problem
« Reply #7 on: February 16, 2008, 07:03:42 PM »
Use mole ratios - every mole of O2 gives 2 mole of H2O.

Offline ARGOS++

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Re: Stoichiometry Problem
« Reply #8 on: February 16, 2008, 07:15:09 PM »
Dear JonathanEyoon;

As C1.)   Write below the Reaction Members the corresponding MWs, and
As C2.)   Write the translated Moles of 5.0g O2 below its MW.

For   D.) you know that the Amount of O2 is the only limiting Reagent.
From E.) and B.) you know  how many moles water you can build from one Mole O2, and so you can calculate the Amount  in Moles and Grams  of Water you have build.     


Good Luck!
                    ARGOS++

Offline JonathanEyoon

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Re: Stoichiometry Problem
« Reply #9 on: February 16, 2008, 07:21:07 PM »
 ??? i'm completely lost.  Is there any way you could do this one problem for me?  I want to see an example of how to do a problem of this kind.  I have 14 more after this one  :-\  Any help is much appreciated.

Offline Arkcon

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Re: Stoichiometry Problem
« Reply #10 on: February 16, 2008, 07:26:16 PM »
yea I know how to find MW and convert to mols.  What do I do from there?

Great.  You're given amounts in units of grams.  The balanced chemical equation is in units of moles.  You want the answer in grams. 

So convert grams of reactant to moles, use the balanced equation to convert moles of reactant into moles of product (hey, why do you think we call it a balanced equation?  It is a function that you've derived, just like mathematics, for the purpose of converting moles of product into moles of reactants.)  Then convert moles of product back into grams, for the answer.
« Last Edit: February 16, 2008, 09:26:04 PM by Arkcon »
Hey, I'm not judging.  I just like to shoot straight.  I'm a man of science.

Offline Arkcon

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Re: Stoichiometry Problem
« Reply #11 on: February 16, 2008, 07:30:42 PM »
??? i'm completely lost.  Is there any way you could do this one problem for me?  I want to see an example of how to do a problem of this kind.  I have 14 more after this one  :-\  Any help is much appreciated.

At least show us that you can determine molecular weight, and convert grams to moles, like you assured us you can.  Then try to follow the steps outlined by ARGOS++.  Sev's suggestion is good as well, but you may need a bit more expertise, before his suggestion becomes intuitive, and not confusing for you.
Hey, I'm not judging.  I just like to shoot straight.  I'm a man of science.

Offline ARGOS++

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Re: Stoichiometry Problem
« Reply #12 on: February 16, 2008, 07:32:06 PM »

Dear JonathanEyoon;

Don’t fear!

From the indices given on B.) you know that from 1 Mole O2 you can build 2 Moles Water.
So Please tell me how many Moles of O2 you have (= 5.0g), and how many Moles of Water you have built.


Good Luck!
                    ARGOS++

Offline JonathanEyoon

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Re: Stoichiometry Problem
« Reply #13 on: February 16, 2008, 07:54:23 PM »
Wait, how do we get 2 H20's from 1 mole of 02?  Don't we need a hydrogen for that to happen?  5.0g of oxygen to mols should be

.3125 moles

How do you find how many moles of water i've built?
« Last Edit: July 19, 2015, 05:16:28 PM by Arkcon »

Offline ARGOS++

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Re: Stoichiometry Problem
« Reply #14 on: February 16, 2008, 08:05:33 PM »

Dear JonathanEyoon;

Sorry!,  ─   
I got 0.15625 Moles, because the MW of O2 is 32.0 and not 16.0!
With an Excess of H2 you can build 2 * 0.15625 Moles Water (from B.)).
How many Water will this now be?


Good Luck!
                    ARGOS++


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