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Compounds

Learn how to interpret chemical formulas by understanding the number of elements in compounds through subscripts and symbols. Practice dimensional analysis to calculate moles and grams for different compounds. Examples provided for better understanding.

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Compounds

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  1. Compounds Unit 2 Topic 2

  2. Chemical Formula • A chemical formula represents the number of each type of element bonded together in a compound. • The number of capital letters indicates how many types of elements are present (each element has only one capital letter).

  3. Subscripts • A subscript directly after an element’s symbol indicates how many of that element there is in the compound (if there is no subscript then there is only one of that element). • H2O Subscript indicates 2 Hydrogen atoms

  4. Symbol • If the symbol of a compound contains parentheses, then the subscript outside the parentheses is multiplied by each element inside the parentheses. • This information is used to determine the number of each type of element in the compound. You will need to be able to do this proficiently before you learn how to add up molecular masses.

  5. Examples • Calcium Phosphate • Ca – 3 • P -- 2 • O -- 8

  6. Examples • Ammonium Carbonate • N – 2 • H – 8 • C – 1 • O – 3 • Total = 14

  7. Dimensional Analysis • Calculate the number of smacks in one lardo 1 lardo 12 tolls 3 smacks = 1 x 12 x 3 = 9 smacks 1 x 4 1 lardo 4 tolls What do I know about lardo? 4 tolls = 3 smacks 12 tolls = 1 lardo 8 lardos = 7 fleas Will either of these help me get to smacks?

  8. Dimensional Analysis • Calculate the number of moles in 7.7 g Na 7.5 g Na 1 mole = 7.5 x 1 = 0.33 moles 22.99 22.99 grams What do I know about Na? Will this help me get to grams? 1 mole Na = 22.99 g

  9. In your spiral: Label this 2.2 • 2 moles of CaF2 = ? Grams 1 mole of CaF2 = 78.06 grams 2 moles x 78.06 grams = 1 mole Calculator: 2 moles x (78.06/1) = 156.12 grams

  10. 2.2 continued • 243.18 grams of CaF2 = ? moles 1 mole of CaF2 = 78.06 grams 243.18 grams x 1 mole = 78.06 grams Calculator: 243.18 x (1 / 78.06) = 3 moles

  11. More problems • 4 moles of Be(OH)2 = ? Grams • 86 grams of Be(OH)2 = ? moles • 0.25 moles of Ba(NO2)2 = ? Grams • 114.66 grams of Ba(NO2)2 = ? moles

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