how to find moles from grams

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Moles are a standard unit of measurement in chemistry that take into account the different elements in a chemical compound.^[1] Often, amounts of compounds are given in grams and need to be converted to moles. This conversion can help give you a clearer picture of the number of molecules you're working with rather than dealing with weight, which can change between molecules. Although the conversion is simple, there are a number of important steps that need to be followed. Using this method, you can learn how to convert grams into moles.

1
Gather the necessary tools for solving a chemistry problem. Having everything you need easily accessible will simplify the process of solving the assigned problem. You will need the following:
- A pencil and paper. Calculations are easier to solve when you write them out. Be sure to show all your steps to get full credit.
- A periodic table. You will need to be able to find atomic weight of elements using the periodic table.
- A calculator. Calculators are necessary to simplify calculations of complex numbers.
2
Identify the elements in the compound that you need to convert into moles. The first step in calculating molecular mass is identifying each element that composes the compound. It is easy to distinguish elements because abbreviations contain only one or two letters.
- If a compound is abbreviated with two letters, the first will be capitalized while the second will be lowercase. For example, Mg is the abbreviation for magnesium.
- The compound NaHCO₃ has four elements in it: sodium (Na), hydrogen (H), carbon (C), and oxygen (O).
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3
Determine the number of atoms that each element contributes to the compound. You must know how many atoms of each element are present to calculate the molecular mass. ^[2] The number of atoms each element contributes will be written in a subscript next to the element.
- For example, H₂O has two atoms of hydrogen and one atom of oxygen.
- If a compound has parentheses followed by a subscript, each element within the parentheses gets multiplied by the number in the subscript. For example, (NH₄)₂S has two atoms of N, eight atoms of H, and one atom of S.
4
Write down the atomic weight of each element. A periodic table is the easiest way to find the atomic weight of an element. Once you locate the element on the table, the atomic weight is usually found underneath the symbol for that element.
- The atomic weight, or mass, or an element is given in atomic mass units (amu).^[3]
- For example, the molecular weight of oxygen is 15.99.
5
Calculate molecular mass. The molecular mass of a substance is calculated as the number of atoms of each element multiplied by the atomic weight of that element. ^[4] Knowing the molecular mass is necessary to convert grams to moles.
- Multiply the number of atoms each element contributes to the compound by the atomic weight of that element.
- Add the total weight of each element in the compound together.
- For example, (NH₄)₂S has a molecular weight of (2 x 14.01) + (8 x 1.01) + (1 x 32.07) = 68.17 g/mol.
- Molecular mass is also referred to as molar mass. ^[5]
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1
Set up the conversion formula. The number of moles you have of a compound can be calculated by dividing the number of grams of the compound by the molecular mass of the compound. ^[6]
- The formula looks like this: moles = grams of compound/molar mass of compound
2

Plug your numbers into the formula. Once you have properly set up the formula, the next step is just putting your calculations into the correct part of the formula. An easy way to check that you have everything in the right place is by the units. Canceling out all the units should leave you with just moles.
3
Solve the equation. Using a calculator, divide the number of grams by the molar mass. The result is the number of moles in your element or compound.
- For example, imagine you have 2 g of (NH₄)₂S and you want to convert it to moles. The molecular mass of (NH₄)₂S is 68.17g/mol. Divide 2 by 68.17, and you have 0.0293 moles of (NH₄)₂S.
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Question

What is the difference between moles and molecules?

1 mole of a substance is gram molecular mass of that substance, which contains 6.022*10^23 constituent particles (i.e. molecules). 1 mole = 6.022*10^23 molecules.
Question

What are the differences in atoms and molecules?

Atoms are fundamental elements with 1 nucleus (made up of neutrons and protons), with electrons revolving around the nucleus. Molecules involve bonding between 2+ atoms, so there are 2+ nuclei in a molecule.
Question

How many moles of CO2 are produced when 0.300 moles of C6H12O6 are fermented?

C6H12O6 = 2 C2H6O (alcohol) + 2 CO2, Since 0.3 moles of C6H12O6 produce 2 CO2, then we have produced 2 x 0.3 = 0.6 moles of CO2.
Question

How many grams of H2SO4 are present in 0.25 mole of H2SO4?

Molar mass of H2SO4 is 98g/mole mass = molar mass.no of moles. 98.0.25 = 24.5 g.
Question

How do I convert milligrams to moles?

Divide the milligrams by 1000 to get x/1000 g. Then, divide the grams by molar mass to get (x/1000 g) / (y g/mol). This gives you x/(1000y) mol.
Question

How do I determine the number of moles of phosphoric acid that contain 2.12g of hydrogen atoms?

Divide the mass of the hydrogen by its molar mass (1.008), then divide that by the number of hydrogens in phosphoric acid, which is three.
Question

How many moles are present in 64g of oxygen?

To find out, you would divide 64 by the molar mass of oxygen, which is close enough to 16. That would leave you with 64/16, which is 4.
Question

How do I calculate the weight of the sample to be taken if its molarity and molecular mass are given?

Since moles = grams of compound/the molar mass, to find the mass, you will need to do mass = molar mass x molarity.
Question

How do I convert moles to grams?

Find the molar mass first, then multiply it to the given amount of moles.
Question

How do I calculate the number of electrons, protons, and neutrons of something?

When you have the element, you can use spur periodic table and the atomic number is the amount of protons, then the electrons is equal to the amount of electrons. Lastly the neutrons you subtract the number of protons from the elements mass number.

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Article SummaryX

To convert grams to moles, start by multiplying the number of atoms by the atomic weight for each element in the compound. Then, add all of your answers together to find the molar mass of the compound. Finally, divide the number of grams of the compound by the molar mass of the compound to find the number of moles. To learn how to find the number of atoms and the atomic weight for each element, read on!

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