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Okay so now we’re on to question number six find the number of ibuprofen molecules in a tablet containing 200 milligrams of ibuprofen okay so this is a multi-step question uh first let’s write out what we are given we’re given the mass of ibuprofen which is 200.0 milligrams but i will convert it to grams just to make it easier for my calculations in the future

I’m just going to write 0.2 grams and then they give us the chemical formula for ibuprofen c13 h18 o2 and we want to find the number of ibuprofen molecules but the first step is to just find the molar mass of ibuprofen so molar mass can be denoted as a capital m of c13 h18 o2 so to find the molar mass of this overall compound we need to first determine all

Of the atomic masses of the individual atoms so these are just values you would find on your periodic table and we want to multiply by however many atoms are in the compound so in the case of carbon there are 13 carbon atoms so we’re going to multiply 13 by the molar mass of carbon plus 18 times the molar mass of hydrogen plus 2 times the molar mass of oxygen

Okay so on the periodic table you’ll find that for carbon it has an atomic num mass of 12.01 grams per mole for hydrogen it is 1.01 grams per mole and for oxygen it is around 16 grams per mole okay so if we multiply it all out we should end up getting a molar mass of 206.31 grams per mole okay so that’s part one of answering the question second part is to now

Find the number of moles of ibuprofen so to do this it is just the mass divided by the molar mass so this is why i converted our 200 milligrams to 0.2 grams just so that it is um i can cancel out the grams when i divide by the molar mass so it’s going to be 0.2 grams divided by 206.31 grams per mole grams will cancel out and our number of moles is 9.69 times

Ten to the negative four okay so lastly we can answer the question find ibuprofen molecules so now we want to convert our moles to molecules and the way we do this is by multiplying by avogadro’s number so avogadro’s number is 6.0 to 2 times 10 to the power of 23 and the units are convenient conveniently molecules over all so this will cancel out our moles

And give us a final answer of 5.84 times 10 to the 20 molecules let me box it okay so the junior tutor said that to solve this we need to recall some concepts first that a mole is the amount of a substance that contains as many elementary entities such as atoms molecules or other particles as there are atoms and exactly 12 grams of the carbon 12 isotope this

Number is called the avogadro’s number which is 6.022 times 10 to the 2 23. that in mind we just need to convert the given amounts in milligrams to its amount in moles by using the molar mass of ibuprofen then we perform dimensional analysis so they showed it all in one line so starting from milligrams they converted it to grams and then divided by the molar

Mass of ibuprofen and then multiplied by avogadro’s number and then got 5.838835 pretty much the same thing so this solution is correct you

Transcribed from video

Find the number of ibuprofen molecules in a tablet containing 2000 mg of ibuprofen C13H18O2 By OneClass