Notes #1: Formula Weight & % Composition

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Presentation transcript:

Notes #1: Formula Weight & % Composition WCHS Chemistry QUIZ FRIDAY!!! NEED PERIODIC TABLES AND CALCULATOR!!!!

CLOSER LOOK: COMPOUNDS NaHCO3 Na2SO4 Sr(NO3)2 Al2(SO4)3 Na = H = C = O = 1 Na = S = O = 2 Sr = N = O = 1 Al = S = O = 2 1 1 2 3 1 4 6 12 3

= the total mass of the elements in a compound FORMULA WEIGHT (FW) = the total mass of the elements in a compound Calculating Formula Weight Find the mass of each individual element Use whole numbers Add all of the element masses together Ex. H2O → H = 1 O = 16 → 1 +1 + 16 = 18!

MORE PRACTICE NaHCO3 Sr(NO3)2 Na = H = C = O = 1 Sr = N = O = 1 1 2 1 6 3

= the mass percent of each element in a compound PERCENT COMPOSITON = the mass percent of each element in a compound To calculate % composition: element mass x 100 Ex. H2O → formula weight H → 2/18 x 100% = 11.1% H O → 16/18 x 100% = 88.9% O

84 MORE PRACTICE NaHCO3 → 23/84 x 100% Na = H = C = O = 1 x 23 PERCENT COMPOSITIONS! NaHCO3 → 23/84 x 100% Na = H = C = O = 1 x 23 = 27.4% Na = 23 → 1/84 x 100% = 1.2% H 1 x 1 = 1 = 14.3% C → 12/84 x 100% 1 x12 = 12 → 48/84 x 100% = 57.1% O 3 x16 = 48 + 84 FORMULA WEIGHT!