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Stoichiometry

Stoichiometry. Standards 3b-d. Vocabulary. Molecular Mass/molar mass- the combined mass of all atoms in a molecule Mole- the amount of substance in EXACTLY 12.0 grams of Carbon-12 Avogadro's number- 6.02 x 10 23

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Stoichiometry

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  1. Stoichiometry Standards 3b-d

  2. Vocabulary • Molecular Mass/molar mass- the combined mass of all atoms in a molecule • Mole- the amount of substance in EXACTLY 12.0 grams of Carbon-12 • Avogadro's number- 6.02 x 1023 • Mole ratio- the number of moles of “A” over the moles of “B” use coefficients from a balanced equation. (FRACTION that you don’t divide.)

  3. What is Stoichiometry? • The study of quantitative relationships based on balanced chemical formulas and chemical equations. • It allows you to predict… • How much reactant you will use • How much product you will make

  4. Molecular Mass • HOW DO WE FIND MOLECULAR MASS • Add up the masses of all atoms in a molecule. • Units are grams/mole (read as grams per mole) • Ex. H2O = 1+1+16=18g • Why do we care what the molecular mass is? • Used to determine how much you have. • If you are taking Tylenol and you have two choices the generic or name brand, the molecular mass of the compound is used to determine the mg of active ingredient.

  5. Converting from grams to moles • What is a mole? • A mole is a unit of measurement that is used to designate atoms and the amount of substance • Invented to make calculations easier. • A mole of a substance is based on pure Carbon-12 • 1 mole of C-12 contains EXACTLY 6.02x1023 atoms

  6. 1 mole comparisons • 1 mole of C-12 is exactly 12.0 gram • 6.02x1023 particles is Avogadro's number • 1 mole of eggs would be 6.02 x1023 eggs, that would take 10 billion chickens laying 10 eggs per day more than 10 billion years to lay a mole of eggs. • My point of all this a mole is a HUGE number!

  7. 602,000,000,000,000,000,000,000 Sextillion, quintillion, quadrillion, trillion, billion, million, thousand, hundred Avogadro's number

  8. Chocolate chip cookies • 1 c. butter • ½ c. granulated sugar • 1 c. brown sugar • 1 tsp. vanilla • 2 eggs • 2 ½ c. flour • 1 tsp. baking soda • 1 tsp. salt • 2 c. semisweet chocolate chips • Makes 3 dozen cookies • How many eggs are needed for 3 dozen cookies? • How much butter is needed for the amount of chocolate used? • How many eggs would we need to make 9 dozen cookies? • How much brown sugar would I need if I had 1 ½ cups of granulated sugar?

  9. How do my cookies relate to chemistry • Recipe is the reaction • Cups and tsp. are moles • Eggs, butter and sugar are chemical compounds • Everything is about ratios

  10. THE MOLE TRAIN multiply by molar mass multiply by avagadro's number Gram Mole Molecule divide by avagadro's number divide by molar mass

  11. Dimensional analysis • Grams given x (1 mole/ molar mass) • Moles given x (molar mass/1 mole)

  12. Converting between grams and molesTHE MOLE TRAIN • Since we are just looking at grams to moles we only use part of the mole train. • To convert from grams to moles we divide by the molar mass • To convert from moles to grams we multiply by the molar mass

  13. Example-mole train method • How many moles of NaOH are in 24.7 grams of NaOH? • Have 24.7 grams NaOH • Want moles of NaOH • To get moles we need molar mass • 24.7 grams/molar mass of NaOH • 24.7/((22.99+16.00+1.01)) • 24.7/40 • 0.6175 moles of NaOH

  14. Example- dimensional analysis method • How many moles of NaOH are in 24.7 grams of NaOH? • Have 24.7 grams NaOH • Want moles of NaOH • To get moles we need molar mass • 24.7 grams X (1 mole/40 grams) (grams and grams cancel out to leave moles) • 0.6175 moles

  15. Moles to grams-mole train • How many grams of CuSO4 are in 7 moles of CuSO4? • Have 7moles grams CuSO4 • Want grams of CuSO4 • To get moles we need molar mass • 7 moles*molar mass of CuSO4 • 7*((63.55+32.07+(4*16)) • 7*135.14 • 945.98 grams CuSO4

  16. Dimensional analysis method • How many grams of CuSO4 are in 7 moles of CuSO4? • Have 7moles grams CuSO4 • Want grams of CuSO4 • To get moles we need molar mass • 7 moles*(molar mass of CuSO4/1mole CuSO4) • 7mole*(135.14grams/mol) (moles cancel to leave grams) • 945.98 grams CuSO4

  17. Practice problems • Find the number of moles • 2.0 grams of NH3 • 0.9 grams of H2O • 5.2 grams of KOH • Find the number of grams • 4.0 moles of NaCl • 3.0 moles of CaCO3 • 2.1 moles of NaBr

  18. Section Review 7.1 all 

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