Molar Mass and Mass Percent

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Molar Mass and Mass Percent
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Molar Mass Review

• Find the molar mass of the following
• NH4
• N 14 g
• H 1 g x 4 4 g
• Total mass 18 g

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Try some

• Na2CO3
• Na 23 g x 2 46 g
• C 12 g
• O 16 g x 3 48 g
• Total mass 106 g
• Ca(NO3)2
• Ca 40 g
• N 14 g x 2 28 g
• O 16 g x 6 96 g
• Total mass 164 g

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Now for something new

• Mass Percent
• Mass mass of element
• ________________ x 100
• mass of compound
• Please note that this is the TOTAL mass of the
  element in the compound

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Mass Percent Sample

• What is the mass percent of each element in 1 mol
  of NaHCO3?
• Step 1 Find the mass of each element in the
  compound
• Na 23 g
• H 1 g
• C 12 g
• O 16 x 3 48 g

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Continuing

• Step 2 Find the mass of the compound
• 23 g 1 g 12 g 48 g 84 g/mol

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Last step

• Find the mass percent of each element using the
  formula given
• Na 23 g Na
• ____________ x 100 27.38 Na
• 84 g NaHCO3
• Do for other 3 elements

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Results

• H 1.19 H
• C 14.29 C
• O 57.14 O
• Be careful to use the TOTAL oxygen!