Stochiometry Involving Moles

        

Today in Class we learnt how to calculate from moles to grams and vice versa.  The  balance equation shows the relationship between moles of the substances nicely.  However in real experiments we deal with the mass of the substances which is in grams.  Therefore we need to know how to convert one way to the other.

Review

How to find the mass of substance B when you are given the mass of substance A?

Solution:  A(grams)--> moles of A-->moles of b--->mass of B(grams)






Road map for all calculation involving Stoichiometry

 



Practice Web#1


 Practice Web#2



Road map focusing on grams to moles

 

Example:

WHAT IS THE MASS OF O2 IS REQUIRED TO REACT WITH 80.0 GRAMS OF CH4?

CH4 + 2O2--> CO2 + 2H2O



Step 1:  Check if the equation is balance.

 Solution:  Each side has 4H, 4O, and 1C.  Thus the equation is balanced.

Step 2:  Convert 80g of CH4 to moles of  CH4

Solution: 80gCH4*1molCH4/16.0gCH4= 5molCH4

Step3:  Convert 5molCH4 to molO2

Solution: 5molCH4*2molO2/ 1molCH4= 10mol of O2

Step 4:  Convert 10molO2 to O2g

Solution: 2.5mol02*32gO2/1molO2= 320g02

Step5:  Check your Sig Figs

Solution: Number use in the quetion was 80.0 so that is three sig figs.  Thus 320g0--->3.20*10^3g of O.