Finding limited reactant (Chem 101)

[legendarium]

Homework Statement

Find the limited reactant: Silver Nitrate and Potassium Chromate mix in a double replacement.

Silver Nitrate: 2.15 mL, 0.153 M ; Potassium Chromate: 1.08 mL, 0.197 M.

The Attempt at a Solution

I balanced and have a chemical reaction of:
2AgNO3 + K2Cro4 -> Ag2Cro4 + 2KNO3

I can solve this problem if i was given the grams of each molecule. But I am not sure how to start the problem with Molarity and Volume.

I think i would need to do this:

0.153 mol AgNO3 /1L (0.00215L AgN03) (2mol KNO3/2mol AgNo3) (101.1 g KNO3/1mol KNO3) = 0.033gAgNo3

So, how does this look? This is only one of the two equations but i can figure the other one out if if this is right.

 

[Borek]

I can solve this problem if i was given the grams of each molecule.

Do you know how to read chemical reaction equation? It is given in terms of moles, so while it can be easily converted to masses, there is no need for that.

By definition

C = \frac n V

Solve for n.

 

[legendarium]

Yes i figured that out last night...

So, is this right?

 

[Borek]

As I told you - don't calculate mass of the reactant, calculate number of moles.

And I have no idea what you did - KNO₃ doesn't play any role here and is not involved.

 

[legendarium]

im assuming my original post is not clear.

i think i did exactly that.

Thank you.

 

[~christina~]

I can solve this problem if i was given the grams of each molecule. But I am not sure how to start the problem with Molarity and Volume.

What you need to find is the mass of the products formed using the amounts of each reactant present at the beginning of the rxn.

0.153 mol AgNO3 /1L (0.00215L AgN03) (2mol KNO3/2mol AgNo3) (101.1 g KNO3/1mol KNO3) = 0.033gAgNo3

The concept is correct but you are mixing up the reactants and the products.

Technically it would be: (using AgNO₃ as the reactant to find product)

(0.00215 L AgNO₃ * 0.153 mol/L AgNO₃)*(1 mol Ag₂CrO₄ / 2 mol AgNO₃)*(331.73g / 1 mol Ag₂CrO₄) = 0.0546 g Ag₂CrO₄

You can figure out the grams of Ag₂CrO₄ produced using the amount of the potassium chromate given. That should tell you which is the limiting reagent.

Hope this helps.

 

[legendarium]

It did, thank you.