An aspirin tablet contains 81.0 mg of aspirin, which has the molecular formula, c9h8o4.

With this you can answer these questions:

How many moles of aspirin are in the tablet? How many molecules of aspirin are in the tablet?

For the number of moles of aspirin use this formula:

number of moles = mass in grams / molar mass

An the molar mass of the C9H8O4 is calculated in this way:

9*12.0g/mol + 8*1.0 g/mol + 4*16.0g/mol = 180 g/mol

mass of aspirin = 81.0 mg = 0,081 g

=> number of moles of aspirin = 0,081 g / 180 g/mol = 0,00045 moles

And the number of molecules is the number of moles times Avogadro's number = >

number of molecules = 0,00045 moles * 6.022 * 10^23 molecules / moles =

= 2.71 * 10^20 molecules.