Name: ______________________________________
Date: ______
Period: _____
WS9.1
I’d like a mole, please Chemists use the mole all the time to figure out how many atoms or molecules are in a substance. The mole is an amount (6.02 x 1023), also know as Avogadro’s number. More importantly, the average atomic mass in grams for each element has exactly one mole of atoms. For example, a mole of carbon has a mass of 12.01 g, and those 12.01 grams contain 6.02 x 1023 atoms of carbon. We can say that the molar mass of carbon is 12.011 grams per mole. If I needed half a mole of carbon I would mass out 6 grams of carbon, and that would contain 3.01 x 1023 atoms of C. Similarly, 24 g of C is 2 moles of carbon, and contains 1.2 x 1024 carbon atoms. Example: What is the molar mass of water, and how many water molecules would it contain? Solution: Water is H2O. We can find the molar mass by adding up the average atomic masses: 2(1.01) + 16.00 = 18.02 grams/mol. Since this is one mole of water, it will contain 6.02 x 1023 water molecules. ______________________________________________________________________________ Use these relationships to answer the questions below. 1. A mole of aluminum contains _____ g of aluminum, and also consists of ____________atoms of aluminum. If I needed 2 moles of aluminum, I would mass out ______ grams of aluminum, recognizing that it contains______________ aluminum atoms. 2. A mole of TNT (trinitrotoluene, C7H5N3O6) NO2 H
H O2N
NO2 H
H
has a mass of ________grams. If I had 0.1 moles of TNT it would have a mass of _________ grams, and would consist of _____________ molecules of TNT. H
3. The lightest element is ________;a molecule of this element has a molar mass of _________g/mol (remember, in this class, like in the real world, we will use the terms molar mass and mole interchangeably). 4. Determine the molar mass of each of the following molecules: A. Sugar (C6H12O6): B. The smell of fish: triethylamine:
N C. Carbon dioxide D. Water
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