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11/18/10

Today's Agenda .th 11/18/10. Recall Have your Comp/Notebooks ready Percent Compositions Empirical Formula Hydrates. 11/18/10. http://teachers.yourhomework.com/blowe/. 1. Lab Tomorrow Website is updated. 11/18/10. http://teachers.yourhomework.com/blowe/. 2. Recall.

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11/18/10

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  1. Today's Agenda .th 11/18/10 • Recall Have your Comp/Notebooks ready • Percent Compositions • Empirical Formula • Hydrates 11/18/10 http://teachers.yourhomework.com/blowe/ 1

  2. Lab TomorrowWebsite is updated 11/18/10 http://teachers.yourhomework.com/blowe/ 2

  3. Recall Find the # of moles of • 1 g of Carbon dioxide CO2 • 1 g of Carbon monoxide CO Find the mass (in g) of • 1 mole Hydrogen chloride HCl • 1 mole Potassium nitrate KNO3Hint: Find the Molar Mass of all Compounds 11/18/10 http://teachers.yourhomework.com/blowe/ 3

  4. Empirical Formula • Empirical Formula – shows the simplest ratio of a compound. • Example: H2OThis shows the simplest ratio of a compound • Non-Example: H4O2This is still water and a chemical formula, but it’s not an empirical formula because it’s not in simplest ratio form. 11/18/10 http://teachers.yourhomework.com/blowe/ 4

  5. Empirical Formula Examples • Write the following chemical formulas in Empirical formula form. • C6H16O2 • Na4S2O8 • Mn4O6 433 11/18/10 http://teachers.yourhomework.com/blowe/ 5

  6. Percentage Composition 333 • Often times, you will be given a percent composition of a substance without knowing the compound. • This means you have to find the Empirical Formula. 11/18/10 http://teachers.yourhomework.com/blowe/ 6

  7. Percentage Composition 444 • Example • Find the Empirical Formula of: • C = 60.0% • H = 13.4 % • O = 26.6% • Find C?H?O? • Assume that you have 100g of each • C = 60.0% x 100g = 60.0 g • H = 13.4 % x 100g = 13.4 g • O = 26.6% x 100g = 26.6 g 11/18/10 http://teachers.yourhomework.com/blowe/ 7

  8. Percentage Composition 444 • Now find the Molar Mass of each element • Molar mass C = 12.01 g/mol • Molar mass H = 1.01 g/mol • Molar mass O = 16.00 g/mo • Calculate the amount of moles for each element: • # of moles C C • # of moles H H • # of moles O O 11/18/10 http://teachers.yourhomework.com/blowe/ 8

  9. Percentage Composition 444 • At this point you can write a chemical formula like this: C5H13.3O1.66 • But you need to get the Empirical Formula because this is not the “simplest” form • Now you take the smallest number “1.66” and divide each number by “1.66” C H O C3H8O1 11/18/10 http://teachers.yourhomework.com/blowe/ 9

  10. 444 Hydrates • Hydrates are anything that has water in it. • Hydrates are a way to say or show how much water is in something • Example: • Cesium Carbonite Dihydrate • Cs2CO2 2H2O • Example: • Cobalt (II) Chloride hexahydrate • CoCl2 6H2O 11/18/10 http://teachers.yourhomework.com/blowe/ 10

  11. 444 Common Prefixes • Hydrate = H2O • di- = 2H2O • tri- = 3H2O • tetra- = 4H2O • penta- = 5H2O • hexa- = 6H2O • hepa- = 7H2O • octa- = 8H2O 11/18/10 http://teachers.yourhomework.com/blowe/ 11

  12. http://teachers.yourhomework.com/blowe/ 44444 Homework • Do the four problems on the mini handout in your comp/notebook. • These problems are also on page 243 in your text book and on-line • This and the notes will count as a stamp for tomorrow.

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