chem_formula

# chem_formula - Unit F Chemical Formulas F.1 Number of Atoms...

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Chemical Formulas F.1 Number of Atoms in a formula NaNO 3 : How many atoms of each element are in this formula? Na: one sodium atom NO 3 : one nitrogen atom and three oxygen atoms Na(NO 3 ) 2 : Na: one sodium atom (NO 3 ) 2 : there is one nitrogen atom in each of the two nitrate ions; 2x1=2 N atoms (NO 3 ) 2 : there is three oxygen atoms in each of the two nitrate ions: 3x2=6 O atoms F.2 Molecular Mass Average mass of molecules compared to the mass of a Carbon-12 atom (amu) formula mass = Σ atomic masses in formula unit Example: Ca(NO 3 ) 2 Calcium Nitrate Ca = 40.1 amu N = 2 x 14 = 28. amu O = 6 x 16. = 96. amu 40.1amu + 28.0amu + 96.0amu = 164.1 amu 164.1amu is the weight of 1 molecule of Ca(NO 3 ) 2 F.3 The Mole Concept One mole is the amount of any substance that contains the same amount of units as the number of atoms in exactly 12g of Carbon 12 mole is equal to 6.02 x 10 23 atoms (Avogrado’s number) example: 6.23 moles of Al question: How many atoms 6.23 moles AL x 6.02 x 10 23 atoms = 3.75 x 10 24 Al atom 1 mole AL how many moles of H 2 O are in 1.67 x 10 21 water molecules? Given:

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chem_formula - Unit F Chemical Formulas F.1 Number of Atoms...

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