FORMULAE CHEMICAL, EMPIRICAL, AND MOLECULAR FORMULA OH MY!

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Presentation transcript:

FORMULAE CHEMICAL, EMPIRICAL, AND MOLECULAR FORMULA OH MY!

CHEMICAL FORMULAE A way of expressing the number of atoms of a compound Write the chemical formula of the following: 1.Sodium chloride____________ 2.Lithium oxide____________ 3.Iron (II) bromide____________ 4.Ammonium sulphide____________

CHEMICAL FORMULAE A way of expressing the number of atoms of a compound Write the chemical formula of the following: 1.Sodium chlorideNaCl 2.Lithium oxideLi 2 O 3.Iron (II) bromideFeBr 2 4.Ammonium sulphide(NH 4 ) 2 S

TYPES OF CHEMICAL FORMULAE Molecular Formula Identifies the number of each type of atom Example: Hexane: C 6 H 14 Empirical Formula Simplest whole number ratio of atoms of each element Example: Hexane: C 3 H 7 Structural Formula Shows the structure of the molecule

FIND THE EMPIRICAL FORMULA SubstanceMolecular FormulaEmpirical Formula WaterH2OH2O MethaneCH 4 BenzeneC6H6C6H6 SulfurS8S8 GlucoseC 6 H 12 O 6

FIND THE EMPIRICAL FORMULA SubstanceMolecular FormulaEmpirical Formula WaterH2OH2OH2OH2O MethaneCH 4 BenzeneC6H6C6H6 CH SulfurS8S8 S GlucoseC 6 H 12 O 6 CH 2 O

FIND THE MOLECULAR AND EMPIRICAL FORMULA’S

EXAMPLE 1: A sample of compound contains g Ag, g S, and g O. Determine its empirical formula.

EXAMPLE 1: A sample of compound contains g Ag, g S, and g O. Determine its empirical formula.

EXAMPLE 1: A sample of compound contains g Ag, g S, and g O. Determine its empirical formula.

EXAMPLE 1: A sample of compound contains g Ag, g S, and g O. Determine its empirical formula.

EXAMPLE 1: A sample of compound contains g Ag, g S, and g O. Determine its empirical formula. Ans: Ag 2 SO 4

EXAMPLE 2: A sample of compound contains 18.7% Li, 16.3% C and 65.0% O by mass. Determine its empirical formula.

EXAMPLE 2: A sample of compound contains 18.7% Li, 16.3% C and 65.0% O by mass. Determine its empirical formula. Ans: Li 2 CO 3

MOLECULAR FORMULA To find the Molecular Formula we use the following relationship Where Molar Mass is the mass of the Molecular Formula Where N = the whole number multiple by which the empirical mass is increased

EXAMPLE 3: A compound has an empirical formula of NH 2 and a molar mass of 32.1 g/mol. List 3 possible molecular formulae. What is the compound’s molecular formula?

EXAMPLE 3: A compound has an empirical formula of NH 2 and a molar mass of 32.1 g/mol. List 3 possible molecular formulae. NH 2, N 2 H 4, N 3 H 6 What is the compound’s molecular formula? N2H4N2H4

EXAMPLE 4: A compound containing 40.0% carbon, 6.7% hydrogen and 53.3% oxygen has an molar mass of g/mol. What is the molecular formula?

EXAMPLE 4: A compound containing 40.0% carbon, 6.7% hydrogen and 53.3% oxygen has an molar mass of g/mol. What is the molecular formula?

EXAMPLE 4: A compound containing 40.0% carbon, 6.7% hydrogen and 53.3% oxygen has an molar mass of g/mol. What is the molecular formula?

EXAMPLE 4: A compound containing 40.0% carbon, 6.7% hydrogen and 53.3% oxygen has an molar mass of g/mol. What is the molecular formula? Molecular Formula: C 6 H 12 O 6

IN-CLASS WORK Download and complete the Empirical and Molecular worksheet from my Website AND… Hebden Questions: p Q’s 46 a,b,c,m,n and 54