 # Unit 2 Lesson #5 Avogadro’s Number & The Mole (p.14-16)

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Unit 2 Lesson #5 Avogadro’s Number & The Mole (p.14-16)
How Big is A Mole?

A. What is the Mole? 1. A counting number (like a dozen)
2. Avogadro’s number (NA) 1 mole =  1023 representative particles

3. Using Dimensional Analysis to Make Conversions
a. Convert 48 eggs to dozens of eggs Conversion factor : 48 eggs X 1 dozen 1 12 eggs b. Convert 6 dozen to number of eggs 6 dozen X 12 eggs 1 1 dozen

4. Molar Conversion Factors
a. # of Particles (atoms, molecules, ions, etc.) 1 mole =  particles b. Molar mass = mass of 1 mole of a substance 1 mole = molar mass c. Molar Volume = 22.4 Liters for any gas at STP (Standard Temperature Pressure) *STP = T = 0o C or 273 K P = 1.0 atmosphere (atm) 1 mole = molar volume

Mole Relationships

Representative Particles & Moles
Substance Chemical Formula Representative Particle Rep Particles in 1.00 mole Carbon C 6.02 x 1023 Nitrogen gas N2 Calcium ion Ca2+ Magnesium fluoride MgF2

Representative Particles & Moles
Substance Chemical Formula Representative Particle Rep Particles in 1.00 mole Carbon C Atom 6.02 x 1023 Nitrogen gas N2 Molecule Calcium ion Ca2+ Ion Magnesium fluoride MgF2 Formula unit

B. Mole to Particle Conversions
6.022  1023 NA MOLES NUMBER OF PARTICLES (particles/mol) Particles = atoms, molecules, formula units, ions, etc NA atoms/mol NA molecules/mol

1. How many molecules are in 2.50 moles of C12H22O11?
6.02  1023 molecules C12H22O11 1 mol C12H22O11 2.50 mol C12H22O11 = 1.51  1024 molecules C12H22O11

2. If you have 2.23 x 1018 atoms of sodium, how many moles is that?
2.23  1018 atoms Na 1 mole Na 6.02  1023 atoms Na 3.70 x 10-6 moles Na =

= 2.26  1024 formula units Ca(OH)2
3. How many formula units is 3.75 moles of calcium hydroxide? 6.02  1023 formula units Ca(OH)2 1 mol Ca(OH)2 3.75 mol Ca(OH)2 = 2.26  1024 formula units Ca(OH)2

C. Molar Mass Conversions
1. Molar Mass = The mass of one mole of an element or compound Atomic mass (on the PT) tells the... mass of each atom (amu) grams per mole (g/mol) 2. Round to 2 decimal places

3. Molar Mass Examples 12.01 g/mol 26.98 g/mol 65.39 g/mol a. carbon
b. aluminum c. zinc 12.01 g/mol 26.98 g/mol 65.39 g/mol

4. Molar Mass Examples H2O 2(1.01) + 16.00 = 18.02 g/mol NaCl
a. water b. sodium chloride H2O 2(1.01) NaCl = g/mol = g/mol

5. Molar Mass Examples NaHCO3 22.99 + 1.01 + 12.01 + 3(16.00)
a. sodium bicarbonate b. sucrose NaHCO3 (16.00) = g/mol C12H22O11 12(12.01) + 22(1.01) + 11(16.00) = g/mol

6. Molar Mass Examples Mg(OH)2 24.31 + 2(16.00) + 2(1.01)
a. magnesium hydroxide b. ammonium sulfate Mg(OH)2 (16.00) + 2(1.01) = g/mol (NH4)2SO4 2(14.01) + 8(1.01) (16.00) = g/mol

D. Molar Mass Conversions
6.02  1023 NA MASS IN GRAMS MOLES NUMBER OF PARTICLES (g/mol) (particles/mol) Particles = atoms, molecules, formula units, ions, etc NA atoms/mol NA molecules/mol

1. How many moles of carbon atoms are in 26 g of carbon?
26 g C 1 mol C 12.01 g C = 2.2 mol C

2. Find the mass of 2.1  1024 molecules of NaHCO3.
1 mol NaHCO3 6.02  1023 Molecules NaHCO3 84.01 g NaHCO3 1 mol NaHCO3 = 290 g NaHCO3

3. How many atoms are in 22.5 grams of potassium?
6.02  1023 atoms K 1 mol K 22.5 g K 1 mol K 39.10 g K = 3.46 x 1023 atoms K

E. Molar Volume Conversions
NA Molar Mass Molar Vol * Molar Volume = 22.4 Liters for any gas at STP

What is the volume at STP of 4.00 g of CH4?
4.0g X 1 mole X L = 5.6 L g mole

2. How many grams of He are present in 8.00 L of He at STP?
8.0 L X 1 mole X grams = 1.4 g L mole