Molecular formulas, Molecular Mass, properties and hydrates Unit 5 Notes #5

Molecular Formulas to Molecular Mass 1.If given the molecular formula, we can calculate the molecular mass. 2.Find the mass of each individual element and add all the masses together 3.Round to the nearest.1 g/mol

Molecular Formulas to Molecular Mass Examples: NH 3 N: 14.0 H: 1.0 (3) = 17.0 g/mol

Molecular Formulas to Molecular Mass Examples: Dicarbon monoxide (C 2 O) C: 12.0 (2) O: 16.0 = 40.0 g/mol

Molecular Formulas to Molecular Mass Examples: Hexafluorine heptabromide (F6Br7) F: 19.0 (6) Br: 80.0 (7) = g/mol

Molecular Formulas to Molecular Mass Examples: SO4 S: 32.0 O: 16.0 (4) = 96.1 g/mol

Ionic vs. Molecular (covalent) compounds Ionic: Crystalline solids at room temp. Strong ionic attractions result in stable structures High melting points and boiling points Ions conduct electric current when dissolved in water

Ionic vs. Molecular (covalent) compounds Molecular (covalent) Gases or liquids at room temperature No attractions which lead to less stable structures Mush lower melting and boiling points There are no ions, so there is no electric current when placed in water

Hydrates Compounds that absorb water into their solid structures form substances called hydrates These substances combine with water in different ratios Hydrates typically have different properties than anhydrous substances (no water) These properties depend on whether or not the compound is hydrated, so we must include the degree of hydration

Lets name hydrates 1.Write the compound as you normally would (just like any binary molecular, ionic, or polyatomic compound) 2.Add a dot (·) and the number of water molecules that you need. 3.When naming, use the correct prefix for the number of water molecules needed 4.Add the word hydrate for the actual water

Examples CuSO 4 ·5H 2 0 The first part is copper (II) sulfate Add the water and it is Copper (II) sulfate pentahydrate

Examples MgSO 4 ·8H 2 O Magnesium sulfate octahydrate Barium chloride dyhydrate BaCl 2 ·2H 2 O

Try these on your own CaSO 4 ·6H 2 O N 4 O 3 ·3H 2 O Calcium chloride dihydrate Copper (II) sulfate decahydrate

Try these on your own CaSO 4 ·6H 2 O – calcium sulfate hexahydrate N 4 O 3 ·3H 2 O – tetranitrogen trioxide trihydrate Calcium chloride dihydrate – CaCl 2 ·2H 2 O Copper (II) sulfate decahydrate- CuSO 4 ·10H 2 O