geez louise there’s a lot of stuff this unit, let’s speed through it all
percent composition is just the percentage of a certain element in a compound
it’s like saying “oh yah that compound is 20% iron” or “bella’s diet is 95% smarties”
steps:
vid: https://www.youtube.com/watch?v=JqKEaPmNFLg&list=PLytGGifnD9dUom302biLWWGuTxg7lgI7P&index=11
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example problem: A compound is 71.65% chlorine, 24.27% carbon, and 4.07% hydrogen. What is the empirical formula of the compound?
Convert %’s into grams (if the question already gives the info in grams, skip this step)
71.65% Cl → 71.65 g Cl
24.27% C → 24.27 g C
4.07% H → 4.07 g H
Convert grams to moles
now divide alll the numbers by the the smallest number of moles
if the numbers aren’t whole, multiply them so they’re whole, we don’t do decimals here
and voila, the numbers u got are now the subscripts for the elements!
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we’re gonna go off the last question from above^, cuz that’s how it’ll be formatted on the test
so: If the molar mass of the previous compound (CH2Cl) is 148.41 g, what is the molecular formula?
find total mass of empirical formula
divide molar mass by empirical mass
148.41 / 49.48 = 3
take that number ^, and multiply all the subscripts of the empirical formula by it, and bada bam boom, you have molecular formula
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