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Mole. The mass of a single atom is too small to measure on a balance. E.g. mass of a hydrogen atom = 1.673x10 -24 g An analytical balance can measure up to 4 decimals. To measure atoms in the real world we need a huge number of atoms. That huge # we define as a mole.
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Mole The mass of a single atom is too small to measure on a balance. E.g. mass of a hydrogen atom = 1.673x10-24 g An analytical balance can measure up to 4 decimals. To measure atoms in the real world we need a huge number of atoms. That huge # we define as a mole. 1 mol = 6.02x1023 This number is called as Avagadro’s number. The number of particles as there are in exactly 12 g of C-12. How big is it? Spreading Avagadro # of marbles over Earth’s surface produce a layer of 3 miles thick.
Avagadro’s Number • Just like 1 dozen = 12 • 1 mole of anything = 6.02x1023 that thing • 1 mole of an element = 6.02x1023 atoms • 1 mole of compound = 6.02x1023 molecules
Example: Converting Moles to Molecules and Atoms • Calculate the number of aluminum atoms in 4.5 mole of aluminum. Conversion factor: 1 mol = 6.02 x 1023 2. Calculate the number of molecules of C8H10 in 0.350 mol of C8H10. 3. Calculate the number of carbon atoms in 0.350 mol of C8H10.
Practice: Converting Moles to Molecules and Atoms 1. How many moles of CO2 are there in 1.0 million of CO2 molecules? 2. How many carbon atoms are there in 225 molecules of C3H8O?