Is there a way to determine how many molecules are in a gram of a substance is so how do you do it?

Answer 1

yes, it is called the molar mass.

look at a periodic table. Below each element is an atomic weight. for instance, Carbon has an atomic mass of 12.011.

A mole is definied as the number of atoms of Carbon-12 would weight 12 grams. this value is 6.023 x 10^23. This means that if u have 12 grams of Carbon-12, then you have 6.023x 10^23 atoms of Carbon-12. If u have 1 gram, then u have (6.023x10^23)/12 atoms of Carbon 12

How u can use this to determine the number of molecules in a certain mass is simple, but u need to know the chemical formula of the chemical. Let's say you have 1 gram of water. Water has the formula H20. The molar mass of Water is the sum of all the atoms,
H has a molar mass of 1.01, and O has a molar mass of 16.00
H20 has two atoms of H and one of O, so multiply the mass of H by two and add the mass of O. H20 then, has a molar mass of 18.02g/mol.

Since you have 1 gram of H2O, then you divide that by the molar mass to determine the number of moles of the substance you have. so:

1g/(18.02 g/mol)= .0555 mol.

And you know 1 mol of Water has 6.02x10^23 molecules of water, so multiply .0555 mol by 6.02x10^23 and get

3.34x10^22

And so u know that in 1 gram of water, there are 3.34 x 10^23 number of molecules

Answer 2

with the molecular weight (MW) of the substance in grams per mole (off the periodic table) you can get the number of moles/grams. Multiply the number of grams by the MW and you have the moles. There are 6.02X10^23 in every mole. So multiply 6.02X10^23 by the number of moles and thats how many molecules you have.

Answer 3

First you take each element, multiply the number of times it occurs in one molecule by the mass number of the element. These are the numbers on the periodic table of the elements(1.007, 4.002, 6.9 etc.) Then you add them together to get the molecular mass. To get the number of molecules in the substance, you take the number of grams, divide by the molecular mass, and multiply by avogadro's number (6.022x10^23)

Answer 4

if you know the chemical formula, then you use that along with the periodic table to get the molecular mass.
then, multiply this by the number of grams to get the number of moles
then multiply the number of moles by avagradro's number, 6.022x10^23 to get the number of molecules