Question

How many molecules of sulfur trioxide are in 78.0 grams?

Answer 1

Almost `6.022xx10^23` sulfur trioxide molecules.

Explanation:

By definition there are `6.022140857(74)×10^23` individual `SO_3` molecules in `80.066` `g` of this material. This represents the MOLAR MASS of sulfur trioxide.

To find the number of `SO_3` molecules, I simply divide the mass by the molar mass, to get a quantity in moles, and mulitply this number by `"Avogadro's number, "6.022140857(74)×10^23`, which is the number of molecules that have a `80.066*g` mass:

`(78.00*cancelg)/(80.0666*cancelg*cancel(mol^-1))` `xx` `6.022140857(74)×10^23*cancel(mol^-1)` `=` `??`