Module 3.docx - Molecular Weight Play the video below for information about Molecular Weight A compound is made up of two or more elements combined in a

# Module 3.docx - Molecular Weight Play the video below for...

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Molecular Weight Play the video below for information about Molecular Weight. A compound is made up of two or more elements combined in a definite ratio which is represented by a molecular formula. Each of these elements has a certain atomic weight which can be found in the periodic table. The sum of the atomic weights of the atoms in the molecular formula is called the formula weight or molecular weight or formula mass . We will use the term molecular weight for this number in our work. Here are three examples of molecular weight determination: Ca 3 (PO 4 ) 2 Molecular Weight = 3 Ca = 3 x 40.08 = 120.24 2 P = 2 x 30.97 = 61.94 8 O = 8 x 16.00 = 128.00 310.18 C 3 H 5 O 2 Cl Molecular Weight = 3 C = 3 x 12.01 = 36.03 5 H = 5 x 1.008 = 5.04 2 O = 2 x 16.00 = 32.00 1 Cl = 1 x 35.45 = 35.45 108.52 Al 2 (SO 4 ) 3 Molecular Weight = 2 Al = 2 x 26.98 = 53.96 3 S = 3 x 32.07 = 96.21 12 O = 12 x 16.00 = 192.00 342.17 Calculate the molecular weight of the following compounds: Na 2 SO 4 2 Na = 2 *22.99 = 45.98 1 S = 1* 32.07 = 32.07 4 O = 4* 16.00 = 64 Total= 142.05 Ca(NO 3 ) 2 1 Ca = 1*40.08 = 40.08 2 N = 2* 14.01 = 28.02 6 O = 6 *16.00= 96 Total = 164.10
K 2 Cr 2 O 7 2 K = 2 * 39.10 = 78.2 2 Cr = 2 * 52.00 = 104 7 O = 7* 16.00 = 112 Total = 294.02 MgI 2 1 Mg= 1*24.305 = 24.305 2 I = 2* 126.9= 253.80 Total= 278.11 Fe(OH) 3 1 Fe = 1*55.85 = 55.85 3 O= 3 *16.00 = 48 3 H= 3* 1.008= 3.024 Total= 106.87 O 2 F 2 2 O= 2*16.00 = 32.00 2 F = 2*19.00 = 38.00 Total= 70.00 Cl 2 O 7 2 Cl= 2 * 35.45= 70.90 7 O= 7* 16.00= 112.00 Total= 182.90 Ca 3 N 2 3 Ca = 3* 40.08= 120.24 2 N = 2* 14.01 = 28.02 Total= 148.26 Li 3 PO 4
3 Li= 3 * 6.941 = 20.823 1 P= 1* 30.97 =30.97 4 O= 4* 16.00 =64.00 Total= 115.79 NH 4 NO 3 1 N= 1* 14.01 = 14.01 4 H= 4* 1.008 = 4.032 1 N= 1* 14.01 = 14.01 3 O = 3* 16.00= 48.00 Total = 80.05 Moles Play the video below for information about Moles. Chemical compounds react with one another in amounts which are based on their molecular weights, this chemically reactive amount of compound is called a mole .

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• Fall '19
• Chemistry, Chemical element, Molecule, Chemical compound, Amount of substance

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