Chapter 3:Stoichiometry

 Key Skills:

 •Balance chemical equations 

•Predict the products of simple aggregate, decomposition, and combustion reactions. •Calculate method weights 

•Convert grams to moles and moles to grams using molar masses. 

•Convert number of molecules to moles and moles to quantity of molecules the usage of Avogadro’s wide variety 

•Calculate the empirical and molecular formulation of a compound from percentage composition and molecular weight. 

•Identify restricting reactants and calculate amounts, in grams or moles, or reactants fed on and merchandise shaped for a reaction.

 •Calculate the percent yield of a reaction.

 Stoichiometry is the study at of the quantitative relationships in materials and their reactions 

 –Chemical equations 

–The mole and molar mass 

 –Chemical formulas 

 –Mass relationships in equations 

 –Limiting reactant 

 Definitions

• Reactants are the materials ate up

• Products are the substances fashioned

• Coefficients are numbers earlier than the 

components of a substance in an equation

• A balanced equation has the identical 

quantity of atoms of every detail on both 

facets of the equation

          Chemical Equations

• A chemical equation is a shorthand notation to 

describe a chemical reaction

– Just like a chemical components, a chemical equation 

expresses quantitative members of the family 

• Subscripts tell the quantity of atoms of every detail in a 

molecule

• Coefficients tell the wide variety of molecules

Coefficients vs. subscripts

Hydrogen and oxygen can make water or hydrogen peroxide

2 H2(g) + O2(g) → 2 H2O(l)

H2(g) + O2(g) → H2O2(l)

Anatomy of a Chemical Equation

Writing Balanced Equations

• Write the appropriate method for every 

substance

H2 + Cl2  HCl

• Add coefficients so the variety of atoms 

of each element are the equal on each 

aspects of the equation

H2 + Cl2  2HCl

Balancing chemical equations 

• Assume one molecule of the most complicated 

substance

C5H12 + O2  CO2 + H2O

• Adjust the coefficient of CO2

to stability C

C5H12 + O2  5CO2 + H2O

• Adjust the coefficient of H2O to stability H

C5H12 + O2  5CO2 + 6H2O

• Adjust the coefficient of O2

to stability O

C5H12 + 8O2  5CO2 + 6H2O

• Check the balance with the aid of counting the quantity of 

atoms of every detail.

Balancing Equations

• Sometimes fractional coefficients are 

obtained

C5H10 + O2  CO2 + H2O

C5H10 + O2  5 CO2 + H2O

C5H10 + O2  five CO2 + five H2O

C5H10 + (15/2) O2  5 CO2 + 5 H2O

• Multiply all coefficients through the 

denominator

2 C5H10 + 15 O2  10 CO2 + 10 H2O