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# How to Calculate Molar Mass

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❶It is used to express concentration of a particular solution. Not Helpful 17 Helpful

## Expert Review By:   Plugging these variables into the basic formula for calculating molarity will give you the correct answer. To calculate molarity, divide the number of moles of solute by the volume of the solution in liters.

If you don't know the number of moles of solute but you know the mass, start by finding the molar mass of the solute, which is equal to all of the molar masses of each element in the solution added together. Once you have the molar mass, multiply the number of grams of solute by 1 over the molar mass to convert the grams into moles. Finally, divide the number of moles by the volume of the solution to get the molarity.

Know the basic formula for calculating molarity. Molarity is equal to the number of moles of a solute divided by the volume of the solution in liters.

What is the molarity of a solution containing 0. Finding molarity demands that you have the number of moles and the number of liters. If the problem provides each of these figures, no preliminary calculations are needed. Divide the number of moles by the number of liters. The resulting quotient will give you the number of moles per liter of solution, otherwise known as molarity. Round off the number of digits after the decimal point to two or three, depending on your instructor's preference.

When you write out the answer, abbreviate "molarity" with "M" and state the chemical abbreviation of the solute involved. Molarity expresses the relationship between the number of moles of a solute per liters of solution, or the volume of that solution. In formula form, molarity is expressed as: What is the molarity of a solution made by dissolving 3.

If you are not provided with the number of moles but you do have the volume and mass of the solution, you will need to use these two figures to calculate the number of moles before continuing on. Find the molar mass of the solute. To calculate the number of moles from the mass or grams of solute used, you must first determine the molar mass of the solute.

This can be done by adding together the separate molar masses of each element found in the solution. Find the molar mass of each element using the periodic table of elements. Make sure that you count the atoms for each element and calculate the molar mass of each of the atoms. Convert the grams into moles. Now that you have the molar mass of the solute, you need to multiply the number of grams of solute in the solution by a conversion factor of 1 mole over the formula weight molar mass of the solute.

This will give you the number of moles of the solute for this equation. Now that you have the number of moles, you can divide this value by the number of liters of solution in order to find the molarity. You should round off the number of digits after the decimal point to the place requested by your instructor. Usually, this will be two or three places after the decimal point. In order to find molarity, you need to calculate the number of moles of solute for a solution per liter of solution.

Milliliters cannot be used. The general formula used to express molarity is written as: What is the molarity of a solution containing 1. Calculating molarity requires you to have the number of moles and the number of liters. If you are provided with the volume in milliliters instead of liters, you will need to convert the volume into liters before continuing your calculations. Convert the milliliters into liters.

Note that you could also simply move the decimal point to the left three places. Now that you have the number of liters, you can divide the number of moles of solute by this value in order to find the molarity of the solution.

Round off the number of digits after the decimal point to the amount requested by your instructor usually two or three places. Find the molarity of a solution made by dissolving 5. Atoms are too small to allow meaningful measurement of chemical substances. To work with meaningful amounts of substances, scientists group them into units called moles.

A mole is defined as the number of carbon atoms in 12 grams of the isotope carbon, which is roughly 6. This number is called Avogadro's number or Avogadro's constant. To calculate the molar mass of an element, find the relative atomic mass of that element, then multiply the relative atomic mass by the molar mass constant. To calculate the molar mass of a compound, calculate the molar mass of each element in the compound, then multiply the element's atomic mass by the number of atoms of that element in the compound.

Add the molar masses of each element in the compound to calculate the molar mass of the compound! Molar mass is the mass in grams of one mole of a substance.

Find the relative atomic mass of the element. An element's relative atomic mass is the average mass, in atomic units, of a sample of all its isotopes. Locate the element and find the number underneath the symbol for the element.

It will not be a whole number, but will have decimals. For example, for hydrogen, the relative atomic mass is 1. Multiply the relative atomic mass by the molar mass constant. This is defined as 0.

This converts atomic units to grams per mole, making the molar mass of hydrogen 1. Some elements are only found in molecules of 2 atoms or more. This means that if you want to find the molar mass of elements that are composed of 2 atoms, such as hydrogen, oxygen, and chlorine, then you'll have to find their relative atomic masses. Multiply them by the molar mass constant, and then multiply the result by 2. This mnemonic stands for hydrogen, oxygen, nitrogen, chlorine, bromine, iodine, and fluorine.

Find the chemical formula for the compound. This is the number of atoms in each element that makes up the compound.

This information is given in any chemistry reference book. For example, the formula for hydrogen chloride hydrochloric acid is HCl; for glucose, it is C 6 H 12 O 6. Using this formula, you can identify the number of atoms of each element that makes up the compound.

For HCl, there is one atom of hydrogen and one atom of chlorine. For C 6 H 12 O 6 , there are 6 carbon atoms, 12 hydrogen atoms, and 6 oxygen atoms. Find the relative atomic mass of each element in the compound. Using the periodic table, locate the relative atomic mass for each element. It is the number located beneath the symbol for the element. The relative atomic masses of the elements in hydrochloric acid are: The relative atomic masses of the elements in glucose are: Tc 43 Technetium Ru 44 Ruthenium Rh 45 Rhodium Pd 46 Palladium Ag 47 Silver Cd 48 Cadmium In 49 Indium Sn 50 Tin Sb 51 Antimony Te 52 Tellurium I 53 Iodine Xe 54 Xenon Cs 55 Caesium Ba 56 Barium Hf 72 Hafnium Ta 73 Tantalum W 74 Tungsten Re 75 Rhenium Os 76 Osmium Ir 77 Iridium Pt 78 Platinum Au 79 Gold Hg 80 Mercury Ti 81 Thallium Pb 82 Lead Bi 83 Bismuth Po 84 Polonium At 85 Astatine Rn 86 Radon Fr 87 Francium Ra 88 Radium Rf Rutherfordium Db Dubnium Sg Seaborgium Bh Bohrium Hs Hassium Mt Meitnerium Ds Darmstadium Rg Roentgenium Cn Copernicium Uut Unutrium Uuq Flerovium UuP Ununpentium Lv Livermorium Uus Ununseptium Uuo Ununoctium La 57 Lanthanum Ce 58 Cerium Pr 59 Praseodymium Nd 60 Neodymium Pm 61 Promethium ## Main Topics

The molar mass is the mass of one mole of a sample. To find the molar mass, add the atomic masses (atomic weights) of all of the atoms in the molecule. Find the atomic mass for each element by using the mass given in the Periodic Table or table of atomic weights.

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Molar massis a unit that enables scientists to calculate the weight of any chemical substance, be it an element or a compound. Molar mass is the sum of all of the atomic masses in a formula. Once one determines the molar mass of a substance, it will be easy to measure out one mole of that substance.