What the heck is a mole? We have Avagadro ( and others) to thank for this…….. 6.02 x 1023 is the number of “things” per mole of the substance. Here is a tutorial for an over view and for a reference as you work through these problems http://www.wiley.com/college/chem/spencer053872/tutorial/gramsmoles/gramsmoles1.html We can use this to do mathematical conversions to determine mass, volume, and number of atoms or molecules in a given substance. For example let’s check out this video to convert moles methane (CH4) to grams of methane. http://www.sciencegeek.net/Chemistry/Video/Unit4/GMV2.shtml Once you have finished the video let’s practice by completing these problems (be sure to include units!):
1. How many moles are represented by 16.0 g of ethanol, C2H5OH ? ❖ C = 12.011g/mol H = 1.00797g/mol O = 16.00g/mol
❖ 2C + 6H + O
❖ *16.0g/(46.07g/mol) = .35 mol
2. How many moles of NaCl are in 16.0 grams of NaCl?
❖ Na = 23.00g/mol Cl = 35.45g/mol
❖ Na + Cl
❖ *16.0g/(58.45g/mol) = .27 mol
3. How many moles of potassium hydroxide, KOH are in 40.6 g? ❖ K = 39.00g/mol O = 16.00g/mol H = 1.00g/mol
❖ K + O + H
❖ *40.6g/(56.00g/mol) = .725g/mol
4. How many moles of glucose, C6H12O6 are in 27.2 g of glucose? ❖ C = 12.011g/mol H = 1.00797g/mol O = 16.00g/mol ❖ 6C +12H + 6O
How are we doing? How about the opposite? What if you want to determine the mass of a substance that is represented by moles? Check this video out………….. http://www.sciencegeek.net/Chemistry/Video/Unit4/GMV1.shtml
Once you are finished let’s practice it again….
1. How many grams in 0.158 moles of KMnO4?
❖ K = 39.00g/mol Mn = 54.93g/mol O = 16.00g/mol
❖ K + Mn + 4O