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Transcript
October 23, 2013 Nomenclature Practice Give the name or the formula: Ag3N calcium acetate CdSO4 copper(I) sulfide ClO3 manganese(III) nitrate Nomenclature Practice Give the name or the formula: Ag3N calcium acetate CdSO4 copper(I) sulfide ClO3 manganese(III) nitrate October 23, 2013 Convert 2.40 grams of copper(II) sulfate to molecules. Main Skills in Chapter 4: Converting between atoms/molecules, moles and grams. Percent Composition Empirical and Molecular Formulas October 23, 2013 Remember that a chemical formula tells us the mole ratio between the elements in a compound. For example, there are two moles of hydrogen for every one mole of oxygen in water. Empirical Formula vs. Molecular Formula Empirical Formula is the reduced ratio of elements in a compound. Molecular Formula is the actual ratio of elements in a compound. Molecular Formula = n(Empirical Formula) October 23, 2013 Example: Methanol contains 37.5% carbon, 12.6% hydrogen and 49.9% oxygen. What is its empirical formula? Example: A compound with a molar mass of 140.3 g/mole contains 85.6% carbon and 14.4% hydrogen by mass. What is its molecular formula? October 23, 2013 Main Skills in Chapter 4: Converting between atoms/molecules, moles and grams. Percent Composition Empirical and Molecular Formulas Convert 5.25 x 1024 atoms of neon into grams. October 23, 2013 What is the percent composition of oxygen in Li3PO4? How many grams of oxygen are in 45 grams of Li3PO4? A compound with a molar mass of 284 g/mole contains 43.7% phosphorous and 56.3% oxygen. What is its molecular formula? October 23, 2013 Atoms/ Molecules Div by 6.022x1023 Moles Mult by 6.022x1023 Mult by MW Grams Div by MW October 23, 2013 Chapter 4: The Mole What is the mole? A dozen is to 12 as a mole is to 6.022 x 1023. Atoms and molecules are very small, so chemists are often dealing with LOTS of particles. October 23, 2013 Molar Mass The mass number listed on the Periodic Table is the average atomic mass of an element based on natural abundance. The most useful unit is grams/mole. For example, 1 mole of carbon has a mass of 12.01 grams and 1 mole of sodium has a mass of 22.99 grams. Molar Mass of Molecules The subscripts in a formula tells you how many of each element are present in the molecule. Example: Calculate the molar mass of NaCl. Example: Calculate the molar mass of Mg(NO3)2 October 23, 2013 Conversions with the Mole and Molar Mass Example: Convert 100 grams of carbon into atoms. Example: Convert 3.4 x 1024 molecules into grams of water. October 23, 2013 For the hydrate lab: You will be using grams to calculate moles. The goal is a molar ratio between moles of anhydrate and moles of water. Percent Composition Formula: Example: What is the percent composition of MgSO4?
