userdata-paziras-Chem51-Chap_06

Massofonemo leofh2o 2mo lh21008g2016g 1mo l o11600g

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Unformatted text preview: cent in a compound. Examples: 1. Barium iodide, BaI2, contains 35.1% barium by mass. How many grams of barium does an 8.50 g sample of barium iodide contain? 8.50 g BaI 2 x 35.1 g Ba = 2.98 g Ba 100 g BaI 2 2. Mercuric sulfide, HgS, contains 82.6% mercury by mass. What mass of mercuric sulfide can be prepared from 60.0 g of mercury? 3. When 12.66 g of calcium are heated in air, 17.73 g of calcium oxide is formed. What is the percent of oxygen in this co mpound? 14 Chemistry 51 Chapter 6 THE MOLE CONCEPT · Chemists find it more convenient to use mass relationships in the laboratory, while chemical reactions depend on the number of atoms present. · In order to relate the mass and number of atoms, chemists use the SI unit mole (abbreviated mol). · The number of particles in a mole is called Avogadro’s number and is 6.02x10 23. 2 1 mol of H atoms……….contains: 6.02 x 10 3 H atoms 2 1 mol of H2 mo lecules……….contains: 6.02 x 10 3 H2 mo lecules 2 2 x(6.02x10 3 ) H atoms 2 1 mol of H2O mo lecules….contains: 6.02x10 3 H2O mo lecules 2 2 x (6.02x10 3) H atoms 2 1 x (6.02x10 3) O atoms 2 + 1 mol of Na+ ions………...contains: 6.02 x 10 3 Na ions · The atomic mass of one atom expressed in amu is numerically the same as the mass of one mole of atoms of the element expressed in grams. Element Mass of one atom Mass of one mo le of atoms H 1.008 amu 1.008 grams Mg 24.31 amu 24.31 grams Cl 35.45 amu 35.45 grams 15 Chemistry 51 Chapter 6 MOLAR MASS · The mass of one mo le o f a substance is called molar mass and is measured in grams. Mass of one mo le of H2O 2 mo l H = 2 (1.008 g) = 2.016 g 1 mo l O = 1 (16.00 g) = 16.00 g 18.02 g Molar Mass Mass of one mo le of Ca(OH)2 1 mo l Ca = 1 (40.08 g) = 40.08 g 2 mo l O = 1 (16.00 g) = 32.00 g 2 mo l H = 2 (1.008 g) = 2.016 g 74.10 g Examples: Calculate the mo lar mass of each co mpound shown below: 1. Lithium carbonate (Li2CO3) 2. Salicylic acid (C7H6O3) 16 Molar Mass Chemistry 51 Chapter 6 CALCULATIONS USING THE MOLE CONCEPT When...
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