Stoichiometry of Precipitation Reactions

In summary, a balanced equation for the reaction is 2Fe(ClO3)3 + 3Li2CrO4-->6LiClO3 + Fe2(CrO4)3. The net ionic equation is 2Fe3+ + 3CrO42--->Fe2(CrO4)3. Then using molarity equations, we find that 0.1M=xmol/.234L. However, we are not sure where to go from here. Any help would be appreciated.
  • #1
k-rod AP 2010
36
0

Homework Statement



What mass of iron(III) chlorate is needed to precipitate all the chromate ions from 234 mL of a 0.100 M lithium chromate solution.


Homework Equations





The Attempt at a Solution



we just started precipitates and my teacher didnt explain the procedure very well so if u can get me on the correct track for solving it, it would be appreciated.

i made a balanced equation for the reaction
2Fe(ClO3)3 + 3Li2CrO4-->6LiClO3 + Fe2(CrO4)3

then the net ionic equation 2Fe3+ + 3CrO42--->Fe2(CrO4)3

then i used molarity equations to find 0.1M=xmol/.234L --> 0.0234 mol Li2CrO4

but i am not sure where to go from here, any help?
 
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  • #2
You have the correct number of moles of lithium chromate. What is the ratio of Iron(III) Chlorate to Lithium Chromate? How many moles then of the Iron Chlorate? So find the formula weight of Iron Chlorate and compute this mass as grams.
 
  • #3
Use the mole ratio to go from mols of lithium chromate to mols of iron chlorate. Once you have mols of iron chlorate, calculate the formula mass and just multiply.

Mols of Lithium Chromate * 2/3 = Mols of Iron Chlorate
(mole ratio)

Mols of Iron Chlorate * Formula mass of Iron Chlorate = Answer!
 
  • #4
Great thanks guys, I got it now. My teacher made it pretty confusing. I appreciate the help.
 
  • #5
Maybe maybe not about your teacher. Some of them can be like that, not most. You find your mole ratios among reactants or products from the written reaction. Your mole ratios are essentially conversion factors.
 
  • #6
symbolipoint said:
Maybe maybe not about your teacher. Some of them can be like that, not most. You find your mole ratios among reactants or products from the written reaction. Your mole ratios are essentially conversion factors.

Just to emphasize, I've always found it best to consider mole ratios as conversion factors. I know some teachers don't really push that through your head, but I find it much easier to think of them exactly that way.
 
  • #7
Yeah when you think about them that way it makes it a lot easier. Once I started to do a lot of these problems it becomes pretty easy
 

1. What is stoichiometry of precipitation reactions?

Stoichiometry of precipitation reactions is the study of the quantitative relationships between the reactants and products in a precipitation reaction. It involves calculating the amount of reactants needed to produce a desired amount of product, as well as determining the limiting reactant and theoretical yield.

2. How is stoichiometry used in precipitation reactions?

Stoichiometry is used in precipitation reactions to determine the amount of reactants needed to produce a specific amount of product, as well as to predict the amount of product that will be formed. It also helps in identifying the limiting reactant, which determines the maximum amount of product that can be formed.

3. What is the purpose of a precipitation reaction?

The purpose of a precipitation reaction is to form an insoluble product, called a precipitate, by combining two or more soluble compounds. This is often used in analytical chemistry to identify the presence of certain ions in a solution.

4. How do you calculate the amount of product formed in a precipitation reaction?

The amount of product formed in a precipitation reaction can be calculated using stoichiometry. This involves determining the mole ratios between the reactants and products, and then using the given amounts of reactants to calculate the theoretical yield of the product.

5. What is the difference between a theoretical yield and actual yield in a precipitation reaction?

The theoretical yield is the maximum amount of product that can be formed according to stoichiometry calculations. The actual yield is the amount of product actually obtained in the reaction. The actual yield is generally less than the theoretical yield due to factors such as incomplete reactions, side reactions, and experimental errors.

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