Atomic mass and THE MOLE Finding grams, moles, atomic mass, and molecules

THE MOLE (mol)-review What is a mole? Avogadro's Number A mole is equal to the number of carbon atoms in exactly 12 grams of pure C12 Avogadro's Number One mole of something contains exactly 6.022 *1023 units This is known as Avogadro’s number

Molar mass vs. Atomic mass Molar mass is the total mass of the compound Molar mass by definition is mass in grams of one mole of a substance Atomic mass is the mass of each individual atom Finding the molar mass XaYb Mass of a moles X + mass of b moles Y Example 1. Find the molar mass of benzene C6H6 2. Find the molar mass of Calcium Carbonate

Converting between moles and grams Grams moles g *(1mole / molar mass)=mol Examples 1. if you have 10 grams of carbon how many moles? 2. if you have 33 grams of sulfur how many moles? 3. if you weigh out 19.3 grams of copper how many moles do you have? Moles grams mol *(molar mas/1 mol)=g Examples 1. if you have 6 moles of hydrogen how many grams? 2. If you have 3 moles of nitrogen how many grams? 3. 5.3 moles of oxygen would be how many grams?

Finding the number of atoms (element) Given grams Atoms= gram*(1mol/molar mass)*(6.022*1023atoms/1 mol) Given moles Atoms= mol * (6.022*1023atoms/1 mol) Given atoms Grams= atoms *(1 mol/6.022*1023atoms)*(molar mass/1mol) Moles= atoms *(1 mol/6.022*1023atoms) Examples Carbon Nitrogen Oxygen

Find the number of moles of a compound A compound has a molar mass similar to that of an atom The molar mass of a compound is the sum of the molar masses of the individual atoms EX. What is the molar mass of H2O? 2 hydrogen’s so atomic mass=1.008 thus hydrogen totals 2.016g 1 oxygen =16.0 The water molecule then has a molecular mass of 18.016g

Finding the number of atoms (compound) Steps Find the molar mass Find the moles of the molecule Find the atoms of molecule Find the atoms of element in the molecule Example: Find the number of molecules of H2CO3 in 43grams, find the number of each atom present in 43 grams

Molar mass  2(1.008)+1(12.01)+3(16.0)=62.03 g Find the number of molecules of H2CO3 in 43grams, find the number of each atom present in 43 grams Molar mass  2(1.008)+1(12.01)+3(16.0)=62.03 g Moles 43grams H2CO3 *1mole/62.03g =0.693 moles Atoms 0.693 moles * 6.022 *1023 molecules/moles= 4.17 * 1023 molecules Atoms of each element Hydrogen => 4.17 * 1023 molecules *2 hydrogen atoms/molecule) =8.34 * 1023 atoms of hydrogen Carbon=> 4.17 * 1023 molecules *1 carbon atoms/molecule) =4.17 * 1023 atoms of carbon Oxygen=> 4.17 * 1023 molecules *3 oxygen atoms/molecule) =1.251 * 1024 atoms of carbon

Practice problems Find the molecular mass Find the number of moles CH4 NaOH PCl5 Find the number of moles 2.0 grams of NH3 0.9 grams of H2O 5.2 grams of KOH Find the number of atoms 2.0 moles of C7H14O2 4.2 grams of C7H14O2 0.93 grams of CaCl2