How do you calculate the number of moles of molecules?

Answer 1

To solve for moles you need either a) particle (atoms, compounds etc.) or b)Mass (grams). From this you can then determine the number moles (mol).

To convert particles to number of moles you must DIVIDE the particle by Avogadro's Number (6.0221415 X 1023). If asked for number atoms, and you are only given the number of compounds, you must then multiply this answer by the number of atoms in the compound.

To convert mass (grams) to number of moles, you must DIVIDE the mass by the molar mass (g/mol) of the substance, that is the atomic mass of each atom [e.g H2O has a molar mass of 2 X 1.00794 g/mol (Atomic Mass of hydrogen X2 as there are 2 H atoms) + 15.9994 g/mol = 18.01528]. Divide the mass (g) of the substance by the molar mass of the substance.

Ex/ Determine the number of moles of a 15.0g sample of H2o?

n= 15.0g/18.01528g/mol

n= 0.833 mol

Ex2/ Determine the number of moles of 7.445 x 105 molecules of H2O.

n=6.0221415 x 1024 molecules/ 6.0221415 x 1023 molecules/mol

n=1.00 x 102 mol

Answer 2

1 mole is Avogadro's Number of particles (whether you're dealing with atoms, molecules, compounds or tennis balls, it makes no difference.)

One mole of any element is equivalent to (atomic mass number) grams of that element. See the examples below.

Ex: H has an atomic mass of about 1.008, and 1mol H weighs 1.008g

Na has an atomic mass of about 22.99, and 1mol Na weighs 22.99g

If you're trying to find the number of moles in a compound given a specific weight, you take the mass (in grams) of the compound and divide by the molar mass of the compound (the combined atomic mass). See examples below.

Ex1: You have 6g NaCl, and you want to convert to moles.

Na (atomic mass) is about22.99, and Cl atomic mass is about 35.45

(22.99g+35.45g) = 1mol NaCl = 58.54g NaCl

6g NaCl/58.54g NaCl = # of mol NaCl

Answer 3

The concentration of the substance divided by the volume of it will determine the number of moles (if you know the molarity) If not, take the weight in grams of the substance and divide by the molar mass (the weight of the elements added together.) The weight per mole is the element's atomic mass number In Grams.

Answer 4

First, weigh the compound. Get the chemical formula, so that you can determine how many atoms of each element are present in the molecule. Look up the gram molecular weight of each element in that compound, using the Periodic Table of elements. You can then put that information together to get the gram molecular weight of the molecule in question. Then divide the weight of the compound that you have, by the gram molecular weight, and the result is the number of moles.

Answer 5

By dividing by Avogadro's number. 6.022 X 10^23. For example;

You have 4.50 X 10^22 atoms of whatever

4.50 X 10^22 atoms of whatever (1 mole whatever/6.022 X 10^23)

= 0.0747 moles of whatever

Answer 6

To calculate the number of moles in a substance, divide the number of atoms or molecules by Avogadro's number (6.022 E23). Alternately, divide the mass of the substance by its molar mass.

Answer 7

Divide the mass (grams) by the molar mass (grams per mol)