Atomic Mass = the weighted average of masses of all naturally-occurring isotopes of an element Chapter 6 Chemical Calculations: Formula Masses, Moles, & Chemical Equations Formula Mass = the sum of the atomic masses of all the atoms represented in the chemical formula Calculate the Formula Mass: SnF 2 Al(OH) 3

The MoleA chemistry counting unit! 1 Mole of an element = the atomic mass in grams

How much is a mole?#/type of particlesmolar mass 1 mole of Al 1 mole of H 2 O 1 mole of NaCl

1 Mole of any element contains the same number of atoms as 1 mole of any other element 1 Mole of a molecular compound contains the same number of molecules as 1 mole of any other molecular compound 1 Mole of an ionic compound contains the same number of formula units as 1 mole of any other ionic compound Particles MolesGrams

1. Find the number of atoms in 3.00 moles of copper: 3.00 mole Cu x 6.02 x atoms = mole Cu 2.Find the number of molecules in mole of CO 2. 3.How many moles of water contain 7.50 x molecules? 4. How many moles of silicon are represented by 1.55 x atoms of silicon? The Mole = a Chemistry Counting Unit

What does a mole look like? CopperCu CarbonC WaterH 2 O SugarC 6 H 12 O 6 SaltNaCl

Calculating Molar Mass of a Compound C2H6OC2H6O (NH 4 ) 2 Cl H2OH2O

Converting Mass to Moles (element) mass (g) x 1 mole = moles molar mass (g) Converting Moles to Mass moles x molar mass (g) = mass (g) 1 mole Example: How many grams of copper are equal to 6.25 mole of copper? Example: How many moles of copper are in 5.00 grams of copper?

Converting Mass to Moles (compound) mass (g) x 1 mole = moles molar mass (g) Converting Moles to Mass moles x molar mass (g) = mass (g) 1 mole Example: How many grams of ethanol (C 2 H 6 O) are equivalent to 2.6 x 10 3 moles of ethanol? Example: A box of salt contains 737 grams of NaCl. How many moles of NaCl are present?

Converting Mass to Atoms Example: How many atoms of copper are in 25.0 grams of copper? mass (g) x 1 mole x 6.02 x atoms = # of atoms molar mass (g) 1 mole Example: Find the number of gold atoms in a ring that contains 12.8 grams of gold.

Subscripts in a chemical formula indicate the number of atoms of each type of element in a molecule: Moles of Elements in a Formula

Writing and Balancing Chemical Equations 1.Write an equation using the correct formulas of reactants & products. CH 4 (g) + O 2 (g) CO 2 (g) + H 2 O (l) 2.The State may be specified solid(s) liquid(l) gas(g) aqueous(aq) 3.Conditions may be written above or below the arrow heat  catalyst Pt

Writing and Balancing Chemical Equations 1.Use Coefficients (in front of formula) to balance 2.Hints: start with the element that has the largest number of atoms do H & O next save free elements for last treat polyatomic ions as single entities (if they do not change) 3.Don’t change any subscripts! CH 4 (g) + O 2 (g) CO 2 (g) + H 2 O (l) Count atoms of each element: C H O Use coefficients to balance each element:

Writing and Balancing Chemical Equations Al (s) + Cl 2 (g) AlCl 3 (s) C 3 H 8 (g) + O 2 (g) CO 2 (g) + H 2 O (l)

Writing and Balancing Chemical Equations Mg (s) + HCl (aq) MgCl 2 (aq) + H 2 (g) Fe (s) + O 2 (g) Fe 2 O 3 (s)

Na 2 SO 4 (aq) + BaCl 2 (aq) NaCl (aq) + BaSO 4 (s) Balancing Equations with Polyatomic Ions: Count ions on each side:

Balancing Equations with Polyatomic Ions: Na 3 PO 4 (aq) + MgCl 2 (aq) NaCl (aq) + Mg 3 (PO 4 ) 2 (s) NaOH (aq) + H 2 SO 4 (aq) Na 2 SO 4 (aq) + H 2 O (l)

Combination Reactions Decomposition Reactions Single Replacement Reactions (Displacement) Recognizing Reactions by Pattern (Chapter 9.1): Double Replacement Reactions (Exchange)

Exchange of Cations & Anions (Double Replacement Rxn) 1.Formation of an insoluble product = precipitation AgNO 3 (aq) + NaCl (aq) AgCl (s) + NaNO 3 (aq) 2.Formation of a molecular liquid (like water) = neutralization HCl (aq) + NaOH (aq) NaCl (aq) + H 2 O (l) 3. Evolution of a gas HCl (aq) + NaHCO 3 (aq) NaCl (aq) + H 2 CO 3 (aq) H 2 O (l) + CO 2 (g)

Classify as Decomposition, Combination, Single Replacement or Double Replacement; Name all compounds/elements: 1.Na 2 S + CuCl 2 2 NaCl + CuS 2.Ca + Cl 2 CaCl 2 3.CaCO 3 CaO + CO 2 4.Zn + CuCl 2 ZnCl 2 + Cu

Balance & Classify as Decomposition, Combination, Single Replacement or Double Replacement 1.Ca + O 2 CaO 2.KClO 3 KCl + O 2 3.ZnCl 2 + AgNO 3 Zn(NO 3 ) 2 + AgCl 4.Zn + HClZnCl 2 + H 2 5.Fe + O 2 Fe 2 O 3 6.BaCl 2 + K 2 SO 4 BaSO 4 + KCl

Balance & Classify as Decomposition, Combination, Single Replacement or Double Replacement 1.CaCl 2 + Na 2 CO 3 CaCO 3 + NaCl 2.Fe 2 S 3 Fe + S 3.Ca + Cl 2 CaCl 2 4.Cu + AgNO 3 Cu(NO 3 ) 2 + Ag 5.PbO + HNO 3 Pb(NO 3 ) 2 + H 2 O

We can also classify chemical reactions by Reaction Type Combustion Reactions – give off heat & light CH 4(g) + 2 O 2 (g) CO 2(g) + 2 H 2 O (g)

Combustion Reactions Reaction of a carbon-containing compound with oxygen to generate heat and light Combustion of a hydrocarbon gives carbon dioxide & water: 2 C 2 H 6 (g) + 7 O 2 (g)4 CO 2 (g) + 6 H 2 O(g) Combustion of a carbohydrate gives carbon dioxide & water: C 6 H 12 O 6 (s) + 6 O 2 (g)6 CO 2 (g) + 6 H 2 O(g)

Classification by Reaction Type Acid-Base Reactions (Neutralization) – give a salt & water H 2 SO 4(aq) + KOH (aq) Oxidation-Reduction Reactions – involve an exchange of electrons Zn (s) + CuSO 4(aq) Precipitation Reactions – an insoluble compound is produced ZnCl 2(aq) + AgNO 3(aq)

Mole Relationships in Chemical Equations Conservation of Mass: in any chemical reaction, the total mass of the reactants is equal to the total mass of the products. 2Ag (s) + S(s) Ag 2 S(s) Atoms: Moles: Mass: Total mass:

28.60 grams of copper reacts with 7.22 grams of sulfur in a combination reaction: Cu + S? Mass: grams Moles: Molar Ratio: What is the product? Chemical Calculations Using Chemical Equations

Empirical Formula of a Hydrate (lab) 5.00 g of CaCl 2  XH 2 O were heated g of the anhydrous salt remain. a)Write a chemical equation for the decomposition of the hydrate. CaCl 2  XH 2 O (s) a)Find the Formula of the hydrate.