Transcript Empirical and Molecular Formulas

Empirical and Molecular
Formulas
Chem Honors – Mr. Patterson and Ms. Chung
Unknown compound, only contains N and O.
Decomposes into 0.608 grams of N and 1.388
grams of O. The molecular mass of the
compound is 92 g/mol.
What is the formula of this compound?
Meaning of subscript in
formulas?
Meaning of subscript in
formulas?
C2H6
Meaning of subscript in
formulas?
C2H6
Meaning of subscript in
formulas?
C2H6
Atom ratios
Meaning of subscript in
formulas?
C2H6
MOLE RATIOS
Unknown compound, only contains N and O. Decomposes into 0.608 grams
of N and 1.388 grams of O. The molecular mass of the compound is 92 g/mol.
What is the formula of this compound?
What is the first step?
Unknown compound, only contains N and O. Decomposes into 0.608 grams
of N and 1.388 grams of O. The molecular mass of the compound is 92 g/mol.
What is the formula of this compound?
What is the first step?
1. Convert grams into moles of each element
Unknown compound, only contains N and O. Decomposes into 0.608 grams
of N and 1.388 grams of O. The molecular mass of the compound is 92 g/mol.
What is the formula of this compound?
What is the first step?
1. Convert grams into moles of each element
2. Find ratio of Nitrogen to Oxygen
Unknown compound, only contains N and O. Decomposes into 0.608 grams
of N and 1.388 grams of O. The molecular mass of the compound is 92 g/mol.
What is the formula of this compound?
1. Grams to Moles of Nitrogen:
Unknown compound, only contains N and O. Decomposes into 0.608 grams
of N and 1.388 grams of O. The molecular mass of the compound is 92 g/mol.
What is the formula of this compound?
1. Grams to Moles of Nitrogen:
0.608 g N
Unknown compound, only contains N and O. Decomposes into 0.608 grams
of N and 1.388 grams of O. The molecular mass of the compound is 92 g/mol.
What is the formula of this compound?
1. Grams to Moles of Nitrogen:
0.608 g N x 1 mol N =
14.0 g
Unknown compound, only contains N and O. Decomposes into 0.608 grams
of N and 1.388 grams of O. The molecular mass of the compound is 92 g/mol.
What is the formula of this compound?
1. Grams to Moles of Nitrogen:
0.608 g N x 1 mol N = 0.0434 mol N
14.0 g
Unknown compound, only contains N and O. Decomposes into 0.608 grams
of N and 1.388 grams of O. The molecular mass of the compound is 92 g/mol.
What is the formula of this compound?
1. Grams to Moles of Nitrogen:
0.608 g N x 1 mol N = 0.0434 mol N
14.0 g
2. Grams to Moles of Oxygen:
Unknown compound, only contains N and O. Decomposes into 0.608 grams
of N and 1.388 grams of O. The molecular mass of the compound is 92 g/mol.
What is the formula of this compound?
1. Grams to Moles of Nitrogen:
0.608 g N x 1 mol N = 0.0434 mol N
14.0 g
2. Grams to Moles of Oxygen:
1.388 g O x 1 mol O = 0.0868 mol O
16.0 g
Unknown compound, only contains N and O. Decomposes into 0.608 grams
of N and 1.388 grams of O. The molecular mass of the compound is 92 g/mol.
What is the formula of this compound?
1. Grams to Moles of Nitrogen:
0.608 g N x 1 mol N = 0.0434 mol N
14.0 g
2. Grams to Moles of Oxygen:
1.388 g O x 1 mol O = 0.0868 mol O
16.0 g
3. Find Ratio of Nitrogen to Oxygen:
Unknown compound, only contains N and O. Decomposes into 0.608 grams
of N and 1.388 grams of O. The molecular mass of the compound is 92 g/mol.
What is the formula of this compound?
1. Grams to Moles of Nitrogen:
0.608 g N x 1 mol N = 0.0434 mol N
14.0 g
2. Grams to Moles of Oxygen:
1.388 g O x 1 mol O = 0.0868 mol O
16.0 g
3. Find Ratio of Nitrogen to Oxygen:
mol N
mol O
Unknown compound, only contains N and O. Decomposes into 0.608 grams
of N and 1.388 grams of O. The molecular mass of the compound is 92 g/mol.
What is the formula of this compound?
1. Grams to Moles of Nitrogen:
0.608 g N x 1 mol N = 0.0434 mol N
14.0 g
2. Grams to Moles of Oxygen:
1.388 g O x 1 mol O = 0.0868 mol O
16.0 g
3. Find Ratio of Nitrogen to Oxygen:
mol N = 0.0434 mol N
mol O
0.0868 mol O
Unknown compound, only contains N and O. Decomposes into 0.608 grams
of N and 1.388 grams of O. The molecular mass of the compound is 92 g/mol.
What is the formula of this compound?
1. Grams to Moles of Nitrogen:
0.608 g N x 1 mol N = 0.0434 mol N
14.0 g
2. Grams to Moles of Oxygen:
1.388 g O x 1 mol O = 0.0868 mol O
16.0 g
3. Find Ratio of Nitrogen to Oxygen:
mol N = 0.0434 mol N = 1 mol N
mol O
0.0868 mol O
2 mol O
Unknown compound, only contains N and O. Decomposes into 0.608 grams
of N and 1.388 grams of O. The molecular mass of the compound is 92 g/mol.
What is the formula of this compound?
1. Grams to Moles of Nitrogen:
0.608 g N x 1 mol N = 0.0434 mol N
14.0 g
2. Grams to Moles of Oxygen:
1.388 g O x 1 mol O = 0.0868 mol O
16.0 g
3. Find Ratio of Nitrogen to Oxygen:
mol N = 0.0434 mol N = 1 mol N
mol O
0.0868 mol O
2 mol O
→ NO2
Unknown compound, only contains N and O. Decomposes into 0.608 grams
of N and 1.388 grams of O. The molecular mass of the compound is 92 g/mol.
What is the formula of this compound?
1. Grams to Moles of Nitrogen:
0.608 g N x 1 mol N = 0.0434 mol N
14.0 g
2. Grams to Moles of Oxygen:
1.388 g O x 1 mol O = 0.0868 mol O
16.0 g
3. Find Ratio of Nitrogen to Oxygen:
mol N = 0.0434 mol N = 1 mol N
mol O
0.0868 mol O
2 mol O
→ NO2
EMPIRICAL FORMULA
Empirical Formula
Empirical Formula
> Formulas derived from mass data, that show the lowest wholenumber ratio of elements in the compound.
Empirical Formula
> Formulas derived from mass data, that show the lowest wholenumber ratio of elements in the compound.
Molecular Formula
Empirical Formula
> Formulas derived from mass data, that show the lowest wholenumber ratio of elements in the compound.
Molecular Formula
> May be a multiple of the empirical formula
Examples of Empirical and
Molecular Formulas
Molecular Formula
Benzene:
C 6 H6
Empirical Formula
Examples of Empirical and
Molecular Formulas
Molecular Formula
Benzene:
C 6 H6
Empirical Formula
CH
Examples of Empirical and
Molecular Formulas
Molecular Formula
Benzene:
C 6 H6
Glucose:
C6H12O6
Empirical Formula
CH
Examples of Empirical and
Molecular Formulas
Molecular Formula
Benzene:
Empirical Formula
CH
C 6 H6
Glucose:
C6H12O6
CH2O
Examples of Empirical and
Molecular Formulas
Molecular Formula
Benzene:
Empirical Formula
CH
C 6 H6
Glucose:
C6H12O
Water:
H2 O
CH2O
Examples of Empirical and
Molecular Formulas
Molecular Formula
Benzene:
Empirical Formula
CH
C 6 H6
Glucose:
C6H12O
CH2O
Water:
H2 O
H2O
How do you convert between
the empirical and molecular
formula?
How do you convert between
the empirical and molecular
formula?
1.
Calculate the empirical mass of the compound
How do you convert between
the empirical and molecular
formula?
1.
Calculate the empirical mass of the compound
Ex. NO2 – empirical mass: 14.0 g/mol + 2 x 16.0 g/mol = 46 g/mol
How do you convert between
the empirical and molecular
formula?
1.
Calculate the empirical mass of the compound
Ex. NO2 – empirical mass: 14.0 g/mol + 2 x 16.0 g/mol = 46 g/mol
2.
Divide the molecular mass by the empirical mass to determine
the scalar factor
How do you convert between
the empirical and molecular
formula?
1.
Calculate the empirical mass of the compound
Ex. NO2 – empirical mass: 14.0 g/mol + 2 x 16.0 g/mol = 46 g/mol
2.
Divide the molecular mass by the empirical mass to determine
the scalar factor
>Unknown compound had molecular mass of 92 g/mol.
>92 g/mol / 46 g/mol = 2.
How do you convert between
the empirical and molecular
formula?
1.
Calculate the empirical mass of the compound
Ex. NO2 – empirical mass: 14.0 g/mol + 2 x 16.0 g/mol = 46 g/mol
Divide the molecular mass by the empirical mass to determine
the scalar factor
>Unknown compound had molecular mass of 92 g/mol.
>92 g/mol / 46 g/mol = 2.
3. Multiply all molar ratios by the scalar factor
2.
How do you convert between
the empirical and molecular
formula?
1.
Calculate the empirical mass of the compound
Ex. NO2 – empirical mass: 14.0 g/mol + 2 x 16.0 g/mol = 46 g/mol
Divide the molecular mass by the empirical mass to determine
the scalar factor
>Unknown compound had molecular mass of 92 g/mol.
>92 g/mol / 46 g/mol = 2.
3. Multiply all molar ratios by the scalar factor
NO2
N2O4
2.
Unknown compound, only contains N and O. Decomposes into 0.608 grams
of N and 1.388 grams of O. The molecular mass of the compound is 92 g/mol.
What is the formula of this compound?
Unknown compound, only contains N and O. Decomposes into 0.608 grams
of N and 1.388 grams of O. The molecular mass of the compound is 92 g/mol.
What is the formula of this compound?
1. Convert grams into moles of each element
Unknown compound, only contains N and O. Decomposes into 0.608 grams
of N and 1.388 grams of O. The molecular mass of the compound is 92 g/mol.
What is the formula of this compound?
1. Convert grams into moles of each element
2. Find ratio of Nitrogen to Oxygen to find empirical formula
Unknown compound, only contains N and O. Decomposes into 0.608 grams
of N and 1.388 grams of O. The molecular mass of the compound is 92 g/mol.
What is the formula of this compound?
1. Convert grams into moles of each element
2. Find ratio of Nitrogen to Oxygen to find empirical formula
3. Compare empirical to molecular mass to find scalar factor
Unknown compound, only contains N and O. Decomposes into 0.608 grams
of N and 1.388 grams of O. The molecular mass of the compound is 92 g/mol.
What is the formula of this compound?
1.
2.
3.
4.
Convert grams into moles of each element
Find ratio of Nitrogen to Oxygen to find empirical formula
Compare empirical to molecular mass to find scalar factor
Multiply the mole ratios in the empirical formula by the scalar factor
to get the molecular formula