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To find the molecular weight (also called the molecular mass or molar mass) of a compound or chemical, you need two things: the molecular formula of the compound and a periodic table.

The molecular formula tells you how many atoms of each element is present in the compound. To find the molecular weight, just add up the atomic weights of each element present in the compound, being sure to multiply by the number of times that atom appears. The atomic weight of each element is found on a Periodic Table.

See the Related Questions and the Web Links to the left for a periodic table with the atomic weight of each element.

Here are some examples:

1) What is the molecular weight of methane, CH4?

The formula for methane is CH4, which means there is one carbon atom (C) and 4 hydrogen atoms. From the periodic table, the atomic weight of carbon is 12.011 grams per mole, and the atomic weight of hydrogen is 1.01 grams per mole. Adding them up, we have

12.01 + (4 × 1.01) = 16.05 grams per mole

2) What is the molecular weight of table salt, or sodium chloride?

The formula for sodium chloride is NaCl. The molecular weight of NaCl is just the sum of the atomic weights of sodium (Na) and chlorine (Cl):

22.99 + 35.45 = 58.44 grams/mole

3) What is the molar mass of octane, C8H10?

Answers: The molar mass of octane is just 8 times the mass of carbon plus 10 times the mass of hydrogen:

(8 × 12.01) + (10 × 1.01) = 106.18 grams/mole

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Related Questions

How many mass of a substance a mole contains?

One mole contain the molar mass of a compound, expressed in grams.


What is the mass in atomic mass units of one molecule of a convalent compound called?

A mole.


One mole of which element has the smallest mass?

The mass in grams of 1 mole of the compound (apex)


When you substitute the unit of grams for amu you obtain what of compound?

When you substitute the unit of grams for amu (atomic mass unit), you obtain the molar mass of the compound in grams per mole. This molar mass represents the mass of one mole of the compound, which is a fundamental concept in chemistry for measuring amounts of substances.


How can you calculate the mass of a mole of the compound?

To find the mass of one mole of a compound you must find the mass of a mole of the component elements and add them together. Just as an added side note the molar mass of any element is that elements standard Atomic Mass as listed on the Periodic Table in grams. An example of this would H2O, hydrogen: 1 mole = 1.0794g/mol, Oxygen: 1 mole = 16.00g/mol. Based on these numbers one calculates the molar mass of H2O to be two moles of Hydrogen and one mole of Oxygen or ~18.16g/mol. I will also offer a second example to help further clarify this idea. For this the chemical compound is glucose C6H12O6. hydrogen: 1 mole = 1.0794g/mol, Oxygen: 1 mole = 16.00g/mol, Carbon: 1 mole = 12.0g/mol. So one calculates that Glucose has a molar mass of six moles of carbon, twelve moles of hydrogen, and six moles of oxygen or ~ 181g/mol. Well hope this helps.


How do you calculate a mole of an atoms weight in grams?

To calculate the weight of a mole of an atom in grams (molar mass), you add up the atomic masses of all the atoms in one mole of the substance. This can be found on the periodic table and is usually given in atomic mass units (amu). The molar mass is expressed in grams per mole.


A student has one mole of an unknown compound in a test tube The mass of the compound is 58.5 g The compound could be -?

The compound could be sodium chloride (NaCl) since its molar mass is 58.5 g/mol, which matches the given mass.


How do you convert between the molar percentage of a compound e.g. CaO and the atomic percentage of the elements e.g. Ca and O?

To convert from the molar percentage of a compound to the atomic percentage of its elements, you can use the molar mass of each element to calculate the number of moles of each element in one mole of the compound. Then, you can use these values to determine the atomic percentage of each element. For example, in CaO, one mole of CaO contains 1 mole of Ca and 1 mole of O. So, the atomic percentage of Ca would be (molar percentage of CaO) * (molar mass of Ca) / (molar mass of CaO), and similarly for O.


How are molarity and molar mass related for a compound?

Molarity is the number of moles of solute per liter of solution, while molar mass is the mass of one mole of a substance. These two concepts are related because the molarity of a compound can be calculated using its molar mass. Molarity is calculated by dividing the number of moles of solute by the volume of the solution in liters.


What is the mass of one mole of CuCL2?

CuCl2 is an ionically bonded compound; therefore, its minimum amount is preferably called a "formula unit" rather than a mole. Its gram formula unit mass is 134.45.


A student has one mole of an unknown compound in a test tube The mass of the compound is 58.5 g The compound could be?

The compound could be sodium chloride (NaCl) since its molar mass is 58.5 g/mol.


How do you find molarity given the percentage mass and its density?

To find the molarity of a solution, you first need to calculate the mass of the solute using the percentage mass and density. Then, convert the mass of the solute to moles using its molar mass. Finally, divide the number of moles of solute by the volume of the solution in liters to find the molarity.