Is there a certain formula for calculating the number of molecules using density?

Question

I have a question that says: how many molecules of hydrogen peroxide were in the whole bottle? and i have to calculate the number of molecules using a density... how is that possible?

Answer 1

Well, the thing you need to know is what the volume of the hydrogen peroxide was (maybe it says on the bottle? or is a given in the question?) Next, using the density you can convert the volume of the hydrogen peroxide to mass. After that, you can calculate the moles of hydrogen peroxide using the molecular weight. Once you have moles, you can convert to number of molecules using avagadro's number. Hope this helps

Answer 2

As you surmise, you cannot do this with density alone. You need additional information.

Do you know the volume of liquid in the bottle?
Do you know the concentration of hydrogen peroxide in the liquid?
Do you know the mass of 1 molecule?

With all that you can answer the question.

Answer 3

weight in grams numerically equal to the atomic weight is one mole, which contains 6.022x10^23 molecules (Avogadro's Number)