February 1 Chemistry 11

Today in class we learned perecent yield and limiting reactants.

Limiting reactants:
the chemical that gets used up first
one reactant has to be completely consumed for it to be a L.R
this can tell you how much of a product can be produced and how much of a product do you need to fully consume another product
to find the L.R. guess which reactant is the limiting reactant and do the calculations to see if you are correct

Example: What is the limiting reactant when 125g of P4 reacts with 323g of CL2 to form Phosphorous trichloride?

P4 + 6CL2 = 4PCl3
125g x 1 mol / 124g x 6 mol / 1 mol x 71g / 1 mol = 431g of Cl2

Cl2 is the limiting reactant because you only need 125g of P4 to consume 431g of Cl2
L.R. = Cl2

here is a youtube video explaing Limiting Reactant


Percent yield there are two parts to this the actual yield and theoretical yield.
The theoretical yield of a reaction is the expected calculated amount
The experimental amount is the actual yield
The formula to calculate the percent yield is actual yield / theoretical yield x 100

Example
The production of urea CO(NH2)2 is given by:
2NH3 + CO2 = CO(NH2)2 + H2O

If 50g of urea are produced when 1 mol of CO2 reacts, find the acual yield, theoretical yield and percentage yield.

Actual yield: 50g
Theoretical yield: 1 mol CO2 x 1 mol / 1mol x 60.1 g = 60.1g

Percent yield : 50g / 60.1 g x 100 = 83%

Here is a video explaing about percent yield.