Test Review

The amount of a substance that contains:  6.02 x particles (atoms, molecules, formula units)  22.4 L (volume)  X grams (molar mass) Put simply: A mole is a unit of  COUNT

To Find Molar Mass: 1)Find the atomic mass of each element 2) Multiply by any subscripts 2)Add

Aluminum Hydroxide Steps:1) Write the Formula for Aluminum Hydroxide 2) List the elements that make up Aluminum Hydroxide 3) Count the number of atoms (subscripts) 4) Multiply the # of atoms by the atomic mass 5) Add them all together

Aluminum Hydroxide Al (OH) 3 Al (1) x 27 =27 O (3) x 16 = 48 H (3) x 1 = 3 78 g/mole

 Dinitrogen Pentoxide  Iron (III) Sulfide  Chlorine gas  Lithium Oxide

 Dinitrogen Pentoxide N 2 O 5 = 108 g/mole  Iron (III) Sulfide Fe 2 S 3 = 208 g/mole  Chlorine gas Cl 2 = 71.0 g/mole  Lithium Oxide Li 2 O = 30 g/mole

To Find Percent Composition: 1) Write the formula of the compound 2) Find the molar mass of the elements 3) Find the total molar mass of the compound 4) DIVIDE each element’s molar mass by the total molar mass of the compound 5) MULTIPLY by 100 to put into percent form

Find the percent composition of : nickel (II) hydroxide Steps: 1) Write the formula for nickel (II) hydroxide 2) Find the molar mass of nickel, oxygen and hydrogen 3) Find the total molar mass of nickel (II) hydroxide 4) Divide each elements molar mass by the total molar mass and multiply by 100

Find the percent composition of : nickel (II) hydroxide Ni(OH) 2 Ni (1) x 59 = 59 / 93 x 100 = 63.4% O (2) x 16 = 32 / 93 x 100 = 34.4% H (2) x 1 = 2 / 93 x 100 = 2.2% 93 g/mole

A. Determine the mass of nickel in 45 g of Ni(OH) 2 45 g x = g Ni B. Determine the mass of oxygen in 45 g of Ni(OH) 2 45 g x = g O C. Based on your answers to part A and B, what must the mass of hydrogen be in 45 g of Ni(OH) 2 45 g g = 0.99 g H

A) Find the percent composition of nitric acid B) Determine the mass of oxygen in 87 g of nitric acid. C) What mass of nitric acid contains 12 g of nitrogen

Nitric Acid = HNO 3 A) Find the percent composition of nitric acid H = 1.6 %, N = 22.2%, O = 76.2% A) Determine the mass of oxygen in 87 g of nitric acid. 87 g x = 66.3 g O A) What mass of nitric acid contains 12 g of nitrogen 12 g / = 54 g HNO 3

 Empirical Lowest whole number ratio of the atoms or moles of the elements in a compound  Molecular The actual number of each kind of atom present in a molecule. (May be the same as the empirical formula)

Empirical CH CH 2 O P 2 O 3 H 2 O CH 3 HO Molecular C 6 H 6 C 6 H 12 O 6 P 4 O 6 H 2 0 C 2 H 6 H 2 O 2

If we know the empirical formula and the molar mass of a compound, we can determine the molecular formula of that compound by finding a multiplier How do you find the molecular formula???? 1) Find the mass of the empirical formula 2) Divide the molar mass of the compound by the mass of the empirical formula – this is your multiplier 3) Multiply the ‘multiplier’ by the subscripts

EmpiricalMolar Mass MultiplierMolecularFormula CH 2 O 90 g P 2 O g HCO2 225 g

EmpiricalMolar Mass MultiplierMolecularFormula CH 2 O 90 g3 C 3 H 6 O 3 P 2 O g3 P 6 O 9 HCO g 5 H 5 C 5 O 10

1. Find the number of moles in 1.25 g of nitrogen pentoxide. 2. Determine the mass of moles of dinitrogen pentoxide 3. Find the number of moles in g of chlorine gas 4. How many molecules are in 15.0 g of silicon tetrafluoride? 5. Convert 45.8 L of fluorine gas at STP to grams

1. Find the number of moles in 1.25 g of nitrogen pentoxide0.013 moles 2. Determine the mass of moles of dinitrogen pentoxide1.35 g 3. Find the number of moles in g of chlorine gas0.008 moles 4. How many molecules are in 15.0 g of silicon tetrafluoride?8.7 x molecules 5. Convert 45.8 L of fluorine gas at STP to grams 77.7 g