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Prentice Hall Chemistry (c) 2005

Prentice Hall Chemistry (c) 2005. Section Assessment Answers Chapter 10. By Daniel R. Barnes Init: 11/25/2008. Stack the boxes Grab the banana. 9. Three ways by which one might measure the amount of a material are:. by mass by volume, and by number of particles (“count”).

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Prentice Hall Chemistry (c) 2005

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  1. Prentice Hall Chemistry(c) 2005 Section Assessment Answers Chapter 10 By Daniel R. Barnes Init: 11/25/2008 Stack the boxes Grab the banana

  2. 9. Three ways by which one might measure the amount of a material are: • by mass • by volume, and • by number of particles (“count”). 10.1 Section Assessment

  3. 10. Avogadro’s number is 6.022 x 1023 There are 6.022 x 1023 molecules in a mole of a substance. Okay, well, if it’s not a molecular substance, like for instance, if it’s a noble gas or a metal, there are 6.022 x 1023atoms in a mole of that substance. 10.1 Section Assessment If the substance is an ionic compound, technically, you have to say that there are 6.022 x 1023formula units in a mole of the substance. There’s no such thing as a “salt molecule”. EXTRA CRUD ALERT!

  4. 11. The molar mass of an element is the element’s average atomic mass, expressed in grams (or grams per mole). Example: the molar mass of gold is 196.97 g/mol. Example: the molar mass of iron is 55.85 g/mol. Example: the molar mass of argon is 39.95 g/mol. 10.1 Section Assessment

  5. 11. The molar mass of an element is the element’s average atomic mass, expressed in grams (or grams per mole). Example: the molar mass of gold is 196.97 g/mol. You don't have to have this part in your answer. You should know by now that Mr. Barnes' answers are longer than your bookwork answers need to be. HOWEVER: Some elements occur as molecules. Most of these are diatomic gases, such as H2, N2, O2, F2, and Cl2. For these diatomic elements, the molar mass of the element is more appropriately expressed as two times the average atomic mass of the element. 10.1 Section Assessment Example: the molar mass of nitrogen gas is . . . 14.01 x 2 = 28.02 g/mol Then, there’s ozone, a rare allotrope of the element oxygen, whose formula is O3. Its molar mass is three times the average atomic mass of oxygen. 16.00 x 3 = 48.00 g/mol

  6. 11. The molar mass of an element is the element’s average atomic mass, expressed in grams (or grams per mole). This part on its own is good enough if that's all you've got in your bookwork. 10.1 Section Assessment

  7. 12. The molar mass of a compound is calculated by . . . Adding up the average atomic mass of every atom in one molecule of the compound. The answer is expressed in grams (or grams per mole) as usual. EXAMPLE: What is the molar mass of carbonic acid, H2CO3? H: C: O: 2 1 3 x 1.01 x 12.01 x 16.00 = 2.02 = 12.01 = 48.00 10.1 Section Assessment 62.03 g/mol

  8. ) 0.2490866 6.022 1.500000000 13. How many moles is 1.50 x 1023 molecules of NH3? 1.50 x 1023 molecules 1 mol x 6.022 x 1023 1 molecules 1.50 1023 10.1 Section Assessment x mol = 0.249 x 10(23-23) mol 6.022 1023 = 0.249 x 100 mol 2.49 x 10-1 mol

  9. 6.022 x 1.75 10.53850 10.5 x 5 52.5 14. How many atoms are in 1.75 mol CHCl3? 6.022 x 1023 1.75 mol molecules 5 atoms x x 1 1 mol 1 molecule CHCl3 = 52.5 x 1023 atoms = 5.25 x 1024 atoms 10.1 Section Assessment

  10. 15. What is the molar mass of CaSO4? Ca: S: O: 1 1 4 x 40.08 x 32.07 x 16.00 = 40.08 = 32.07 = 64.00 10.1 Section Assessment 136.15 g/mol

  11. Sorry! No 10-2 yet! Under construction soon!

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