Aspirin can be represented by the adjacent ball-and-stick...

Aspirin can be represented by the adjacent ball-and-stick molecular model. Give the formula for aspirin, and calculate its molecular mass (red $=\mathrm{O},$ gray $=\mathrm{C},$ ivory $=\mathrm{H} )$. How many moles of aspirin are in a tablet weighing 500 mg? How many molecules?

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Key Concepts

Molecular Formula

The molecular formula specifies the types and numbers of atoms present in a molecule using element symbols and numerical subscripts. It is the fundamental representation of a compound’s composition and serves as the starting point for further calculations, such as molecular mass.

Molar Mass Calculation

Molar mass is determined by summing the atomic masses of all atoms in a molecule as indicated by its molecular formula. This value, usually expressed in grams per mole, allows one to quantitatively relate the mass of a substance to the number of molecules it contains.

Mass-to-Mole Conversion

This concept involves converting the mass of a substance to the amount in moles by dividing the given mass by the substance’s molar mass. It is essential for quantitative chemical analysis and stoichiometry in chemical reactions.

Avogadro's Number

Avogadro's number, approximately 6.022×10^23, represents the number of elementary entities (molecules, atoms, ions, etc.) in one mole of a substance. It provides a critical link between the macroscopic and microscopic scales in chemistry.

Transcript

00:01 Here we're given the ball and stick model for aspirin.

00:04 Given the color key where gray or black is carbon, we can see that this molecule has 1, 2, 3, 4, 5, 6, 7, 6, 7, 8, 9 carbon atoms.

00:16 In white or ivory, we have 1, 2, 3, 4, 5, 6, 7, 8 hydrogen atoms and 4 oxygen atoms.

00:27 So that is our formula.

00:31 Next, we need its molecular mass.

00:34 Remember that molecular mass is in units of a &u, and you need a periodic table.

00:39 So for carbon, we have nine carbon atoms, and we have nine times molecular mass of carbon, which is 12 .01.

00:52 We have eight hydrogens whose atomic mass is 1 .01.

01:01 And finally, four oxygens, which has 16 .1.

01:07 As its atomic mass.

01:10 Now remember, your mileage may vary.

01:12 You or your textbook or your instructor might have a different periodic table with different number of significant figures.

01:21 This particular periodic table only goes out to two decimal places, the one in your textbook.

01:26 In this particular textbook goes out to one.

01:29 So just use whatever periodic table or instructions your instructor gives you for calculating molecular math.

01:39 When i put this sum into my calculator, i get 180 .17...

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