Limiting Reactants,Yield and Empirical Formulas

This week in class we talked about limiting reactants, yield and empirical formulas. We learned that in some chemical reactions there are not unlimited amounts of both of the reactants. In order to figure out the reactant that is limiting the reaction, we used a type of stoichiometry.

To view the lecture on limiting reactants click here. 
 Limiting Reactants Steps:
Step 1: Write out the mass of one of the reactants
Step 2:Do a times and a line and bring down grams. It should be 1 mol/molar mass.
Step 3: Do a times and a line and bring down moles. use the mole ratio between the reactant and the product.
Step 4: Do a times and a line and bring down moles of the product. It should be molar mass/ 1 mol
Step 5: Multiply all of the numerators together and divide by all of the denominators.
Step 6: Repeat steps 1-5 for all other reactants. Compare all of the results and find the smallest amount of product. This means that this is the reactant that is limiting the reaction.

To learn about limiting reactants in class we did a POGIL called Limiting and Excess Reactants.

The next thing that we learned this week was percentage yield. We talked about the difference between theoretical yield and actual yield.  Theoretical yield is what you are suppose to get from a reaction and is found by performing calculations. It is the largest amount of product that is possible to create from a given amount of reactant.  It is very rare to get 100% of yield in real life. This is where actual yield comes in. Actual yield is the measured amount of a product produced during a reaction from a given amount of reactant. Click here to see the lecture on yield.

Percentage Yield Steps:
1. Balance the equation.
2. Find the limiting reactant for the chemical reation.
3. Find the theoretical yield.
4. Divide the actual yield by the theoretical yield and multiply by 100. 

Our last topic this week was empirical formulas and mass percent. We learned that an  empirical formula is a formula that is the simplest ratio among the elements of a compound.

 Empirical Formulas:
1. Take the percents of the the elemental analysis and change them to grams by assuming that the total is out of 100 grams.
2.Multiply the grams of an element by 1mol/ molar mass. repeat for each element in the compound.
3.  Divide the answers by the lowest answer.
3. Round all other answers to nearest number, unless a common fraction like 1/2, 1/3, 2/3, 1/4 is in the decimal. If this happens multiply all of the subscripts by the numerator of the fraction to get the empirical formula.

To determine the molecular formula from the empirical formula we divide:
molecular molar mass/empirical molar mass

This number is then used as a scale factor for the empirical formula and is multiplied by all of the other subscripts.


We did an Empirical Formulas POGIL in class to better help us understand this concept.

Mass Percent:
To find the mass % of an element you multiply the number of that type of element by its atomic mass and then divide by the formula weight of the compound. Finally multiply by 100.

To find the mass % of a component we learned that you take the mass of the component divided by the total mass of the substance.Finally multiply by 100.

Over all I felt that I understood the material well. I would give my understanding of this week's material a 9. I'm giving this rating because I was able to understand it well enough to be able to help others also understand. I also only gave it a 9 because I'm still learning everyday and I don't think that I know every single thing  about this topic, but I do have a good understanding of the basic concepts.

I liked how we did white boarding in class this week because it helps me to make sure that I'm doing problems correctly. It is also a good way to collaborate between table partners and share ideas about problems.