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Transcript of MOLAR MASS
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. Multiply the subscript (number of atoms) times the atomic mass of that element and add the masses of all of the elements in the molecule to get the molecular mass. Molar mass usually is expressed in grams (g) or kilograms (kg). sample problem : Supposing we are asked to determine the formula mass of CaCl what are we to do? The first thing to do is to look at the atomic mass of calcium and chlorine from the periodic table. Calcium has an atomic mass of 40.08 and chlorine has 35.45.We need to get the sum of the atomic masses of the atoms in the formula . Hence, 2 CaCl 2 Cl +2 atoms of Cl * (35.45 g) Ca + 1 atom of Ca * (40.08) Thge formula mass of CaCl is 110.98; therefore the mass of one mole or simply the molar mass of CaCl is 110.98 g/mole. The unit mole may be abbreviated as mol. 2 What is the molar mass of Sucrose
C H O ? 12 22 11 to determine the molar mass of sucrose, we need to compute for its molecular mass. The procedure in determining the molecular mass is the same as that of the formula mass. C H O 12 22 11 C 12 - 11 * 916.00 g ) = 176.0g H 22 - 22 * ( 1.00g) = 22.0 g O 11 - 12 * (12.01g) = 144.1 g 342.1 g mole The molecular mass of sucrose is 342.1. Therefore, the molar mass of sucrose is 342.1 g/mol. 3. H SO Determine the molar mass of each of the following substances. 1. NaCl 2. H O 2 2 4 Chemists have devised a way to determine the number of atoms present in a given substance . This is done through a counting unit known as MOLE.
Mole of a substance contains as many atoms , molecules ions or other elementaryunits as the number of atoms in 0.012 or 12.00 g of carbon 12. One moleof any substance always contains the Avogadro's number of particles which is equal to 6.02 8* 10 . 23 To make the ' mole concept' more concrete , let us define it in terms of a mass of substance. It has been defined that the mass in grams of one mole of any substance is equal to its formula mass or molecular mass. This is known as the molar mass, which means mass per mole of a substance.
Mass of 1 mole = formula mass or molecular mass expressed in grams