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Sample Problems:

Sample Problems:. 1. How many grams are in 45 L of neon gas at STP?. 1 mol 22.4 L. 20.180 g 1 mol. 45 L. = 41 g. Sample Problems:. 2. How many formula units are in 36.4 g of NaCl ?. 6.02 x 10 23 form.units 1 mol. 1 mol 58.443 g. 36.4 g. = 3.75 x 10 23 formula units .

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Sample Problems:

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  1. Sample Problems: • 1. How many grams are in 45 L of neon gas at STP? 1 mol 22.4 L 20.180 g 1 mol 45 L = 41 g

  2. Sample Problems: • 2. How many formula units are in 36.4 g of NaCl? 6.02 x 1023form.units 1 mol 1 mol 58.443 g 36.4 g = 3.75 x 1023 formula units

  3. Sample Problems: • 3. What is the mass of 550 L of helium gas at STP? 1 mol 22.4 L 4.003 g 1 mol 550 L = 98 g

  4. Sample Problems: • 4. How many liters are in 5.6 x 1024 atoms of helium gas at STP? 5.61024 atoms 1 mol 6.021023atoms 22.4 L 1 mol = 210 L

  5. Find % sodium in Na2O. Molar mass = Na 22.990 x 2 = 45.98 O 15.999 x 1 = 15.999+ 61.979 g % Na = Part Whole 45.98 g 61.979 g = X 100 = 74.19 %

  6. Find the % composition of a compound that has 5.34g C, 0.42g H, & 47.08g Cl. Mass (total)= 5.34g + 0.42g + 47.08g = 52.84g %C = 5.34g C x 100% = C 52.84g %H = 0.42g H x 100% = H 52.84g %Cl = 47.08g Cl x 100% = Cl 52.84g 10.11 % 0.79 % 89.10 %

  7. How many grams of sodium are in 650.0 g of Na2CO3? Na: X ___= _________ C: X ___= __________ O: X ___ = __________ TOTAL: (Whole) 45.98 22.990 2 12.011 12.011 1 15.999 47.997 3 105.988

  8. Formula: part x grams(total) = Answer whole grams Na = x 650.0 g 45.98 105.988 = 282.0 g Na

  9. 4) Calculate the percent composition of C3H7OH (2-propanol).

  10. Percent composition Homework page 15

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