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Topic: excess reagent problem-i'm stumped  (Read 6373 times)

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Newt

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excess reagent problem-i'm stumped
« on: February 21, 2006, 05:38:21 PM »
OK, so here is my problem:

lithium carbonat reacts with hydrochloric acid

1) Write the balanced equation.

Here is what I get:

Li2CO3 + 2HCl ---> 2LiCl + CO2 + H2O


2) What is the excess reagent?

I think this is a 1:2 ratio;
The reaction requires 1 M (one mole) lithium chloride with 2 M (two moles)hydrochloric acid

So, does it follow then that HCl is the excess reagent because more moles of HCl (2 versus 1) are required in the reaction?

3) What happens to the excess reagent at end of experiment?

I guess since it is in ecess, it is NOT used up and remains in some form, right?

I am NOT provided any value concerning the amount of lithium carbonate and hydrochloric acid.

Is this a trick question or I am I just blind here :D

Any help that anyone can give on this probelm is greatly appreciated!! This one has been stumping me all day!

Offline mike

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Re:excess reagent problem-i'm stumped
« Reply #1 on: February 21, 2006, 07:54:20 PM »
1) Looks right to me

2) I don't think you can tell which reagent is in excess unless you know how much you have. Note that 1M means 1 mole.L-1 and not 1 mole, so was this given to you or did you write this piece of information as this makes a difference. If you had 1 mole of lithium carbonate and 2 moles of HCl then neither reagent is in excess, according to your equation.

3) Presumably you are correct.


Now you say that you are not told the amounts of reagents, is this a question from a book or from a lab?

If I were to guess I would suggest using the HCl in excess from a practical point of view.
There is no science without fancy, and no art without facts.

Newt

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Re:excess reagent problem-i'm stumped
« Reply #2 on: February 21, 2006, 08:56:58 PM »
1) Looks right to me

2) I don't think you can tell which reagent is in excess unless you know how much you have. Note that 1M means 1 mole.L-1 and not 1 mole, so was this given to you or did you write this piece of information as this makes a difference. If you had 1 mole of lithium carbonate and 2 moles of HCl then neither reagent is in excess, according to your equation.

3) Presumably you are correct.


Now you say that you are not told the amounts of reagents, is this a question from a book or from a lab?

If I were to guess I would suggest using the HCl in excess from a practical point of view.

This was some problem that my teacher handed out in class last friday (I was sick that day). My friend told me that NO quantity was provided for lithium carbonate and hydrochloric acid. maybe it was a trick question hehe

But I think you are right. I will go with HCl as the excess reagent. I will let my teacher know about the 1 M v. 2 M situation amount, and that if those were the amounts of the two reactants in the balanced equation, then there would not be any excess reagent.

I thank you for your *delete me*!

Newt :D

Offline arnyk

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Re:excess reagent problem-i'm stumped
« Reply #3 on: February 21, 2006, 10:06:22 PM »
You would need to know at least one quantity of at least one of the reactants or products.

jtlbb2

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Re:excess reagent problem-i'm stumped
« Reply #4 on: February 21, 2006, 10:38:44 PM »
I will let my teacher know about the 1 M v. 2 M situation

I think what he was trying to get at was that "M" isn't a good abbreviation for "mole".  Because "M" means Molarity, which is moles/1liter (moles per liter).

Offline mike

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Re:excess reagent problem-i'm stumped
« Reply #5 on: February 21, 2006, 11:11:45 PM »
Quote
I think what he was trying to get at was that "M" isn't a good abbreviation for "mole".  Because "M" means Molarity, which is moles/1liter (moles per liter).

Spot on, this is exactly what I meant. :)
There is no science without fancy, and no art without facts.

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