Wednesday, January 20, 2010

January 20, 2010

Stoichiometry

  • The coefficients in balanced equations represent moles
  • Also conversion factors
  • what you need/what you have

Example #1

How many moles of Sodium metal are needed to react with 0.0250 mol of Magnesium Chloride

Balanced equation: MgCl2 + 2Na ----> 2NaCl + Mg

0.0250mol MgCl2 X 2Na/1 MgCl2 = 0.0500mol of Na

Example #2

How many grams of oxygen is needed when 0.480mol of water is produced?

Balanced equation: 2H2 + O2 ----> 2H2O

0.480mol H20 X 1O2/2H20 = 0.240mol of O2

Then use the mol to find g

o.240mol X 32g/ 1mol = 7.8 grams of O is needed

* Make sure you take time to balance the equation properly

This ties together everything we've learned so far...pretty easy huh?

http://www.youtube.com/watch?v=-W9-sNfM5Xo

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