Molecules per Gram An aspirin tablet, C9H8O4, contains 0.360 g of aspirin. (The rest of the tablet is starch or other fillers.) How many molecules of aspirin are present in this tablet?

Question

Molecules per Gram . An aspirin tablet,[latex] C_{9} H_{8} O_{4} [/latex], contains 0.360 g of aspirin. (The rest of the tablet is starch or other fillers.) How many molecules of aspirin are present in this tablet?

Accepted Answer

The formula weight of aspirin is 9 (12.0) + 8(1.0) + 4(16.0) = 180.0 amu, which gives us the conversion factor 1 mol aspirin = 180.0 g aspirin. To convert moles of aspirin to molecules of aspirin, we use the conversion factor 1 mole aspirin = [latex] 6.02 imes 10^{23} [/latex] molecules of aspirin.

First we need to find out how many moles of aspirin are in 0.360 g:

[latex]0.360 \cancel{g aspirin} imes \frac{1 mol aspirin}{ 180.0 \cancel{g aspirin} } = 0.00200 mol aspirin[/latex]

The number of molecules of aspirin in a tablet is

[latex]0.00200 \cancel{ mol } imes 6.02 imes 10^{23} \frac{molecules}{\cancel{ mol } }= 1.20 imes 10^{21} molecules[/latex]

Question 4.6: Molecules per Gram An aspirin tablet, C9H8O4, contains 0.360...

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