#### Transcript of Chapter 3 Mass relationship in chemical reaction

**Chapter 3**

Mass

Relationships

in

Chemical

Reactions

Atomic mass unit (amu)

1) For atoms ---> Atomic mass (amu)

2) For molecules ---> Molecular mass (amu)

3) For formula units ---> Formula mass (amu)

In general ---> molar mass (g/mol)

Finding Moles

1) Moles (mol) = Mass (g) / molar mass (g/mol)

2) Moles (mol) = # of particles / 6.02x 10^23

Finding % composition

of element in compound

n x molar mass of element/ molar mass of compound x 100 %

Finding Empirical and

Molecular formula

1) Percentage (%)

2) Mass (g)

3) Moles (mol)

4) Smallest whole-number ratios

5) ---> Empirical formula (EF)

6) (Emprical mass) n = Formula mass

7) ---> Molecular formula (MF)

Stoichiometry

1) Balance the chemical equation.

2) Determine known (reactant) and unknown (product)

3) Convert known (mass) into moles.

4) Use coefficients (

molar ratio

) to relate the known to unknown

5) Solve for unknown (in moles)

6) Convert unknown into mass

7) Identify limiting reactant (LR) and excess reactant (ER)

8) Choose the

least

amount of product (based on LR) = thereotical yield

9) Calculate percent yield if given actual yield

10) Percent yield (%) = actual yield (g)/ theoretical yield (g)

Average Atomic Mass (AAM)

1) AAM= Sum of (isotopic mass x fractional abundance)

2) AAM= Sum of (isotopic mass x percentage abundance)/ 100

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