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Notes #3: STP WCHS Chemistry
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So far… only 1 way to count molecules
Moles = How many molecules ONLY for: PURE solids, liquids & gases (compounds & elements) Moles = Mass FW
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MOLES OF A GAS STP = Standard Temperature & Pressure
“Perfect world” conditions (always for us!) :) Standard Temp = 0o C Standard Pressure = 1 atm IMPORTANT! The volume of 1.00 mole of ANY gas under STP is 22.4 Liters!
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All take up the same amount of space (volume) !
EXAMPLES 1 mole Helium (He) vs. 1 mole Nitrogen (N2) vs. 1 mole SF6 All take up the same amount of space (volume) ! Think of this like a parking lot… There are 602 sextillion parking spaces… Only 602 sextillion cars can fit, but the cars can be all different sizes
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All take up the same amount of space (volume) !
1 mole Helium (He) mole Nitrogen (N2) mole SF6 Volume of 22.4 Liters Volume of 22.4 Liters Volume of 22.4 Liters But no matter what, 1 mole of any gas ALWAYS has a volume of 22.4 Liters!!!
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Moles of = volume in Liters gas at STP 22.4
NEW FORMULA! Moles of = volume in Liters gas at STP Like a universal formula weight! :)
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To go from mL to L, MOVE DECIMAL 3 times to LEFT!
QUICK REFRESHER To go from mL to L, MOVE DECIMAL 3 times to LEFT! 1475. mL mL mL 1.475 L 0.056 L L 2 Things to Remember: Don’t do any rounding after converting! Number & unit must match. Ex: 0.17 L, 170 mL
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RECAP! 2 EQUATIONS FOR FINDING MOLES
Be careful! Are we talking about a mass (grams)? Moles = mass FW Are we talking about a gas at STP (liters)? Moles of = volume in Liters gas at STP
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QUICK REFRESHER ON MOLES
1 mole = 602 sextilltion molecules HOW WE COUNT MOLECULES!!!! Na P → Na3P 3 Na P Na Na P Na 6 Na P → 2 Na3P Na P Na Na P Na P Na Na Na P Na ONCE YOU KNOW MOLES OF ONE THING, YOU KNOW MOLES OF EVERYTHING
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