How many moles of aspirin are present in 100 mg of aspirin? Enter your answer in scientific notation.

5.5E-4

or should it be rounded to 5.6?

I have 5.5507E-4. You are allowed 3 s.f. from the 100 so I would round that to 5.55E-4. I think you shorted yourself 1 place that you should keep.

If allowed only two s.f. I would have rounded to 5.6E-4.

To find the number of moles of aspirin present in 100 mg, you need to use the formula:

moles = mass (in grams) / molar mass (in grams per mole)

First, convert the mass of aspirin from milligrams (mg) to grams (g). Since there are 1000 mg in 1 g, 100 mg is equal to 0.1 g.

Next, you need to determine the molar mass of aspirin. Aspirin has a molecular formula C9H8O4. The atomic mass of carbon (C) is 12.01 g/mol, the atomic mass of hydrogen (H) is 1.008 g/mol, and the atomic mass of oxygen (O) is 16.00 g/mol.

So, the molar mass of aspirin is:
9 (atoms of carbon) * 12.01 g/mol +
8 (atoms of hydrogen) * 1.008 g/mol +
4 (atoms of oxygen) * 16.00 g/mol = 180.16 g/mol

Finally, you can calculate the number of moles of aspirin:
moles = 0.1 g / 180.16 g/mol = 0.000555 moles

When expressed in scientific notation, this is approximately 5.5 × 10^-4 moles.