Avogadro's Number & STP

1. Avogadro's Number & STP ICS III Week 5

2. The Mole • Use the molar mass of an element or compound to convert between the mass of a substance and the moles of a substance CONVERSION FACTORS

3. Moles • 1 dozen = 12 units • 1 gross = 144 units • 1 mole = 6.02 x 1023 units (molecules) • 602,000,000,000,000,000,000,000 molecules

4. Avogadro’s Number • 6.02 x 1023 atoms/molecules in 1 mole • Known to have high accuracy!! • Avogadro’s Number is also a conversion factor!!!!!!!!!!!

5. Moles • Beaker of Water • Mass of water is 18 g • How many moles?? • 1 mole • 1 mole H2O = 18 g • How Many Molecules? • 6.02 x 1023 • 6.02 x 1023 molecules in 1 mole of water!!

6. Moles • Beaker of HCl • Mass of HCl is 36.5 g • How many moles?? • 1 mole • 1 mole HCl = 36.5 g • How Many Molecules? • 6.02 x 1023 • 6.02 x 1023 molecules in 1 mole of HCl!!

7. 1 mole of ANYTHING = 6.02 x 1023 molecules

8. CST Question

9. Convert from grams to moles • Convert from moles to molecules

10. Last Mole Conversion • Gas Laws • 1 mole of gas takes up 22.4 L of space. He O2 CH4 1 mole 1 mole 1 mole 22.4 L 22.4 L 22.4 L 2 g/mol 32 g/mol 16 g/mol

11. Gas Law • 1 mole = 22.4 L • This is only true at Standard Temperature & Pressure (STP)!!! • 0oC or 273 K & 1 atm or 760 mm Hg (Temperature) (Pressure) • If the temperature or pressure changes, then 1 mole = 22.4 L will not hold true anymore!

12. Changing STP Temperature = 0oC Pressure = 1 atm Moles = 1 Volume = 22.4 L Molecules = 6.02 x 1023 What happens when I increase the pressure??? What has changed??? Volume has decrease, pressure has increased. Everything else stays the same!!!!!

13. Volume of Gas @ STP 1 mole 22.4 L 22.4 L 1 mole MOLE Molar mass 1 mole 1 mole 6.02 x 1023 6.02 x 1023 1 mole 1 mole Molar mass Mass in Grams (g) Particles

14. Molar mass 1 mole 1 mole Cr Molar Mass 1 mole Cr 52 g Cr 6.02 x 1023 atoms Cr 1 mole Cr X X