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Stoichiometry: Mathematics of chemical formulas and equations

Stoichiometry: Mathematics of chemical formulas and equations. mole = (mol) 602000000000000000000000. Mole. A mole is just a number pair = 2 trio = 3 quartet = 4 dozen = 12 baker’s dozen = 13 gross = 144. Avogadro’s Number. 6.02x10 23. How BIG is a mole?.

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Stoichiometry: Mathematics of chemical formulas and equations

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  1. Stoichiometry: Mathematics of chemical formulas and equations

  2. mole = (mol) 602000000000000000000000 Mole • A mole is just a number pair = 2 trio = 3 quartet = 4 dozen = 12 baker’s dozen = 13 gross = 144

  3. Avogadro’s Number 6.02x1023

  4. How BIG is a mole? There are ~ 6.6 billion people on Earth How many Earths would it take to equal the population of 1 mole? 9.12 x 1013

  5. If you had a mole of cats . . . They would create a sphere larger than Earth!

  6. If you had a mole of $$$$$ and you spent $800 billion dollars a day how many years would it take to spend a MOLEion dollars? 2.06 x 109 years

  7. If you had a mole of H2O could you swim in it? NO! Water molecules are so small that a mole of H2O = 18ml

  8. How small are atoms? • There are more atoms in one gram of salt than grains of sand on all the beaches of all the oceans in all the world.

  9. Just one granule of sugar contains 1 x 1017 molecules • Each time you take a breath of air, you inhale about 2 x 1022 molecules of nitrogen and 5 x 1021 molecules of oxygen.

  10. In chemistry we don’t work with individual atoms or molecules because they are too small to be weighed or measured • We have to work with LOTS of atoms in order to measure them THAT’s WHERE THE MOLE COMES IN!

  11. The number of grams in a mole is different from substance to substance. If you're like most students, it's this  that's confusing you. Picture it this way: a dozen elephants have a different weight than a dozen rabbits- but in each case, you have a dozen animals. Similarly, a mole of oxygen gas has a different weight than a mole of water- but in each case, you have 6.02×1023molecules.

  12. Why use moles? You often want to know how many molecules you have in a sample of a substance. Counting the molecules individually would be completely impractical. Even if you had a way to see the individual molecules, there are just too many, even in a tiny sample. Moles were defined to solve the problem of counting large numbers of molecules. With moles, you count the number of molecules in the sample by weighing it.

  13. of the in Gram ATOMic Mass • mass in grams is equal to 1 mole of atoms of an element • In other words…… 1 mol C atoms = 6.02 x 10 23 C atoms = 12g C

  14. PracticeRemember . . .1 mole = 6.02x1023atoms or molecules =______ g from the periodic table

  15. Stoichiometry of Chemical Formulas

  16. of the in Gram Formula MassGram Molecular Mass Molar Mass • mass in grams of 1 mole of a substance • In other words . . . Add it all up! 1 mole of NaCl = 58g = 6.02x1023 particles of NaCl 1 mole of H2O = 18g = 6.02x1023 molecules of H20

  17. Now….. • Use the gram formula mass and the gram atomic mass to determine • how many moles or atoms of an element are found in some mass of a substance • how much mass that element contributes to the mass of the entire substance Use factor label & follow the units!

  18. Stoichiometry of Chemical Formulas • If you have 1 molecule of (NH4)2SO4 • How many atoms of N are there? • How many atoms of H? SO….. • If you have 1 mole of of (NH4)2SO4 • How many moles of N are there? • How many moles of H?

  19. “it’s a simple matter of weight ratios . . .” Stoichiometry of Chemical Equations • The study of quantitative relationships that can be derived from chemical equations.

  20. Stoichiometry cookies • If you look at chemical equations as recipes it may be easier to understand that • changing the amount of a reactant will change the amount of the product IN THE SAME RATIO!

  21. Examining Molar Relationships in Balanced Equations 6CO2 + 12 H2O + 2804kJ  6O2 + C6H12O6 +6H20 Balanced equations • Law of conservation of mass / matter • ATOMS are not createdor destroyed during a chemical reaction, they are only rearranged to form new substances. • # atoms on reactant side = # atoms on product side • Law of conservation of E • E on the reactant side = E on the product side

  22. Mole - Mole Relationships Practice

  23. Types of Chemical Reactions

  24. SYNTHESIS Reaction • 2 or more reactants combine to build a single product General Formula: A + B  AB 3H2 + N2 2NH3

  25. Particle Diagram

  26. DECOMPOSITION reaction • A compound is broken down into 2 or more simpler substances General Formula: AB  A + B 2H2O  2H2 + O2

  27. Particle Diagram

  28. SINGLE REPLACEMENT reaction • One of the reactants is a single element. It becomes part of a compound as a product. General Formula: A + BX  B + AX Mg + CaBr2 Ca + MgBr2

  29. Particle Diagram

  30. DOUBLE REPLACEMENT reaction • TWO elements switch places during the process of the reaction. General Formula: AB + CD AD + CB LiCl + KBr LiBr + KCl

  31. Particle Diagram

  32. Combustion • Oxygen is always a reactant • CO2 and H2O are always products • _______ + O2 CO2 + H2O

  33. Practice • 2Al + 3CuSO4 Al2(SO4)3 + 3Cu • 2H2 + O2  2H2O • C12H22O11  11H2O + 12C • KCl + AgNO3  KNO3 + AgCl • CH4 + 2O2  CO2 + 2H2O

  34. The End

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