[Shade3]

Hi all I am working on a chem question that i am having a bit of trouble with, I was hoping you guys could let me know if I am going in the right direction.

Q: How many grams of sulphuric acid will neutralize 10.0g of sodium hydroxide?

Ok so I figured lets start of with a balanced equation, so:

2NaOH + H2SO4 -> Na2SO4 + 2H2O

So I know there are 10g of NaOH so I found the Molar mass of NaOH (44.997109 g/mol) and then found the number of moles of NaOH (n = mass / molar mass) .  i found n = 0.222 mol.

This is where I am unsure if I am right.  I just figured since there are 2 mols of NaOH and only 1 mol of H2SO4 in the balanced equation, the # of mols for H2SO4 must be n = 0.111 mol.

I then found the mass of H2SO4 to be ( 0.111 mols X 98.07948 g/mol = 10.9g) 10.9g.

Am I right about this or did I make a mistake somewhere, I am unsure about stoichiometry and things like that.

[Borek]

Check molar mass of NaOH. Otherwise, approach is OK, just the numbers are wrong

[Shade3]

ok thx alot.  does 39.9971g/mol sound more accurate for the Molar mass of NaOH?

[Borek]

Yep. Although in most cases just 40 will do

[Arv]

Hey, what kind of program were you using in that picture, and is it possible for me to get that.

thanks

[Borek]

EBAS, see my signature.

[Arv]

Thanks

[Shade3]

Ok I've been having trouble on one other question.  I've been trying to figure it out the past hour or so but I seem to be hopelessly lost hehe.

Q: Consider the following reaction, which takes place in an autoclave at 523K and 800atm.

NH3 + 7/4O2 --> NO2 + 3/2H2O

Into the reaction vessel has been placed 200L of NH3 and 120L of O2.  The reaction is allowed to go to completion.  Determine the quantity, in moles, of the gas that remains unreacted.

Ok so that's the question, and I'm kind of stuck  I don't really understand excess too well, I mean the equation is balanced so why is one in excess?  the example given to me to help solve the problem hasn't been helpin me too much hehe.

I honestly don't even know where to start, I know you guys probably don't want to just answer my question so could you maybe give me a push in the right direction? hehe any help is appreciated thx! 

[enahs]

I mean the equation is balanced so why is one in excess?

The equation is just an outline of what will happen. For every mole of NH3 you need 7/4th a mole of O2; according to your equation.

Now, you have 200 L of NH3 and 120L of O2.
How many mols of each do you have? If it reacts according to your equation; which one do you have more of and which one is the limiting reagent? How much of it is left?

[Shade3]

How is volume related to mols though?  I don't know how to find moles if I dont know the mass of one of the substances.  Can I just use ratios?  I don't know how to involve the volume  .  And how do I know how much of the 200L goes to the NO2 and to the H2O?

[Shade3]

oh wait i forogt about my PV = nRT formula I think i can use that to find mols... ok lets see if that gets me anywhere

[Borek]

oh wait i forogt about my PV = nRT formula I think i can use that to find mols... ok lets see if that gets me anywhere

You are right - you can use it to find moles. But you may go shorter route - http://en.wikipedia.org/wiki/Avogadro's_law - ratio of ideal gas volumes is identical with ratio of moles...

[Shade3]

Ok so I found the # of mols, but I don't understand how this helps me.  How do I know how much of the given volumes are transferred to the products, and to which products?

[Borek]

Start calculating what volume of oxygen will be needed to fully react 200 L of nitrogen. Don't worry about the real amount of oxygen - just calculate how much is needed.

[Shade3]

Im not sure I know how to do that.  Do you mean to fully react NH3?  K so I figured I have 3135 mols of NH3 and 9143 mols of O2.  How do I use that info to find the real amount of oxygen needed in volumes.  I'm sorry I know I keep asking the same questions but I don't get it I am very confused, thx for trying to help me though.