Question

How many molecules of aspirin (formula mass aspirin = 180 amu) are in a 0.250-gram sample?

Answer 1

Take the quotient...`"mass"/"molar mass"`...and,,,,

Explanation:

And so, for `C_9H_8O_4` we gots a molecular mass of `180.16*g*mol^-1`...

And so `"moles of aspirin"=(0.250*g)/(180.16*g*mol^-1)=0.001388*mol`

And to get the number of molecules we simply multiply this molar quantity by the `"Avocado number"`....

`0.001388*molxx6.02214xx10^23*mol^-1=8.36xx10^20` individual aspirin molecules....