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Stoichiometry

Stoichiometry. AKA Chemistry Math. How many atoms are in a mole of carbon?. BELL RINGER. Ridiculous Mole Facts. 3 moles of M&M’s would fill the entire earths oceans (an equivalent amount of water would fill about a ¼ cup). 1 mole of donut holes will cover the earth to a depth of seven miles!.

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Stoichiometry

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  1. Stoichiometry AKA Chemistry Math

  2. How many atoms are in a mole of carbon? BELL RINGER

  3. Ridiculous Mole Facts 3 moles of M&M’s would fill the entire earths oceans (an equivalent amount of water would fill about a ¼ cup) 1 mole of donut holes will cover the earth to a depth of seven miles! 1 mole of pennies would reach to the moon 7-8 times.

  4. Ridiculous Mole Facts One mole of seconds is about 19 quadrillion years, 4,240,666 times the age of the earth, or 954,150 times the age of the universe itself. A one liter bottle of water contains 55.5 moles of water. Avogadro's number of kilograms is just over 20 times the mass of the earth.

  5. Are all moles created equally? VS In chemistry, how an atom reacts is dependent on the number of atoms, not the mass of the atoms. • For example, if you have 100.0 g of Na and react that with 100.0 g of Chlorine they would not react completely. • Chlorine starts out with a mass of 35.5 and Na has a mass of 23 • As a result, we would have a bunch of Na atoms unused. • In chemistry it is much easier to use a quantity of atoms rather than a mass of atoms

  6. Moles What is the mass of a Carbon atom? 12.0 amu If one mole of Carbon atom’s have a mass of 12.0g, how many atoms would that be? That would be 6.02 x 1023 atoms of carbon

  7. 18.0 g/mol Gram Formula Mass(molar mass) = the mass of one mole of something Let’s try out water: H2O Therefore, 1 mole of water has a mass of 18g/mol. H 2 x 1.0 = 2.0 = 16.0 O 1 x 16.0

  8. 58.3 g/mol GFM (practice) Let’s try magnesium hydroxide: Mg(OH)2 Mg x 24.3 = 24.3 1 x 16.0 = 32.0 O 2 x 1.0 H 2 = 2.0

  9. What is the gfm of NH4? BELL RINGER GFM = 18Moles = 72.0 ÷ 18.0 = 4 moles

  10. Molar Mass Practice 6. C6H12O6 1. NaBr 2. PbSO4 7. Fe3(PO4)2 3. Ca(OH)2 8. (NH4)2S 4. Na3PO4 9. Zn(C2H3O2)2 10. AgF 5. (NH4)2CO3

  11. GFM Practice 6. C6H12O6 1. NaBr 102.9 g/mol 180.0 g/mol 2. PbSO4 7. Fe3(PO4)2 303.3 g/mol 357.4 g/mol 3. Ca(OH)2 8. (NH4)2S 74.1 g/mol 68.1 g/mol 4. Na3PO4 9. Zn(C2H3O2)2 164.0 g/mol 183.4 g/mol 10. AgF 5. (NH4)2CO3 126.9 g/mol 96.0 g/mol

  12. Number of moles = given mass (g) gram-formula mass 63g 18g/mol Number of moles = Converting to moles If you have 63g of water how many moles of water do you have? 1. Determine the gfm: 18 g/mol = 3.5 moles

  13. 164.1 g/mol Number of moles = given mass (g) gram-formula mass 10.2g 164.1g/mol Number of moles = Some Practice Criss-cross to get the formula: Ca(NO3)2 • What is the gfm for Calcium nitrate? Ca 1 x 40.1 = 40.1 N 2 x 14.0 = 28.0 O 6 x 16.0 = 96.0 2. How many moles of calcium nitrate do you have if you have 10.2 g? = 0.0622 moles

  14. Number of moles = given mass (g) gram-formula mass ConversionsMoles to Grams 1. How many g are in 0.0700 moles of H2O2? 2. How many g are in 1.2 moles of CaCO3?

  15. Number of moles = given mass (g) gram-formula mass 40.8 g 122.6g Number of moles = Practice Problems 1. If you have 40.8g of KClO3. How many moles do you have? GFM = 122.6 g = 0.333 moles 2. You have 2.5 moles of KClO3. How many grams is that? GFM = 122.6 g Grams = GFM x # moles Grams = 122.6g/mol x 2.5 moles = 306.5 g = 310 g

  16. You have 72.0g of NH4. How many moles do you have? BELL RINGER GFM = 18Moles = 72.0 ÷ 18.0 = 4 moles

  17. 18.0 g Percent Composition -used to find the percentage by mass of an element in a compound What are the % of elements in dihydrogen monoxide? H2O H 2 x 1.0 = 2.0 %= 2.0/18.0 = 11.1% 1 x 16.0 = 16.0 O %= 16.0/18.0 = 88.9%

  18. 101.1 g Percent Composition What are the % of elements in potassium nitrate? KNO3 K 1 x 39.1 = 39.1 % = 39.1/101.1 = 38.7% N 1 x 14.0 = 14.0 % = 14.0/101.1 = 13.8% = 48.0 O 3 x 16.0 % = 48.0/101.1 = 47.5%

  19. 237.9 g/mol Percent Composition Hydrate What is the percentage of water in the following compound CoCl2•6H2O Co 1 x 58.9 = 58.9 % = 58.9/237.9 = 24.8% Cl 2 x 35.5 = 71.0 % = 71.0/237.9 = 29.8% = 108.0 H2O 6 x 18.0 % = 108.0/237.9 = 45.4%

  20. Percent Composition Hydrate What is the percentage of water in the following compound CaSO4•5H2O Ca 1 x 40.1 = 40.1 S 1 x 32.1 = 32.1 = 64.0 O 4 x 16.0 = 90.0 x 18.0 5 H2O % = 90.0/226.2 = 39.8% 226.2 g/mol

  21. Hydrate Lab

  22. How many grams is 0.36 moles of potassium permanganate? BELL RINGER

  23. Empirical and Molecular Formulas H2O CH2O CH2OH HO BH3 CH2O

  24. Empirical and Molecular Formulas Empirical Formula = the formula of a compound expressed as the smallest possible whole-number ratio of subscripts of the elements in the formula Molecular Formula = the formula of a compound in which the subscripts give the actual number of each element in the formula

  25. Determining Formulas from % Percent to mass Mass to moles Divide by small Multiply ‘til whole A compound consists of 72.2% magnesium and 27.8% nitrogen by mass. What is the empirical formula? 1. Assume 100g, so you have: 72.2g Mg and 27.8g N 2. Convert to moles Mg - 72.2/24.3 = 2.97 moles N – 27.8/14.0 = 1.99 moles

  26. Determining Formulas from % Percent to mass Mass to moles Divide by small Multiply ‘til whole 3. Divide by small Mg 2.97 / 1.99 = 1.49 Mg1.49N1 ??? N 1.99 / 1.99 = 1 4. Multiply ‘til whole Mg 1.49 X 2 = 3 Mg3N2 N 1 X 2 = 2

  27. A 50.51 g sample of a compound made from phosphorus and chlorine is decomposed. Analysis of the products showed that 11.39 g of phosphorus atoms were produced. What is the empirical formula of the compound?

  28. In the following example the empirical formula of an iron-oxygen compound will be • determined. At the start of the experiment the mass of iron was 16.76 g. At the end of the • experiment the mass of the iron-oxygen compound was 23.96 g.

  29. Percent Composition Lab

  30. What are the empirical formulas for the following?C6H6CH2ClCH3HC2H3O2 BELL RINGER

  31. As a result the formula would be: Na2SO4 BELL RINGER Problem: A compound contains 32.4% sodium, 22.1% sulfur and 45.0% oxygen. What is the empirical formula? • Na 32.4g • S 22.1g • O 45.0g ÷ 23.0 ÷ 32.1 ÷ 16.0 = 1.41 mol = 0.688 mol = 2.81 mol ÷ .688 ÷ .688 ÷ .688 = 2.05 = 1.00 = 4.09

  32. CHEMICAL REACTIONS Reactants: Zn + I2 Product: Zn I2

  33. Lavoisier 1788 Chemical Equations Because of the principle of the lawconservation of matter, an equation must be balanced. It must have the same number of each kind of atoms on both sides.

  34. Chemical Equations Their Job: Depict the kind of reactants and products and their relative amounts in a reaction. Al (s)+ O2 (g) ---> Al2O3 (s) The numbers in the front are called stoichiometric ____________ 4 3 2 coefficients

  35. Symbols Used in Equations • Solid (s) • Liquid (l) • Gas (g) • Aqueous solution (aq) • Catalyst H2SO4 • Escaping gas () • Change of temperature ()

  36. Balancing Equations When balancing a chemical reaction you may add coefficients in front of the compounds to balance the reaction - • but you may notchange the subscripts. • Changing the subscripts changes the compound. Subscripts are determined by the valence electrons (charges for ionic or sharing for covalent)

  37. Subscripts vs. Coefficients • The subscripts tell you how many atoms of a particular element are in a compound. The coefficient tells you about the quantity, or number, of molecules of the compound.

  38. Why are we learning this? • The coefficients of a chemical reaction indicate relative amounts of reactants and products. Coefficients are MOLE RATIOS Example: H2(g) + Cl2(g)  2HCl(g) 1 mol H2 : 1 mol Cl2 : 2 moles HCl • The relative masses of the reactants and products can also be determined from the coefficients. Example: 1 mol H2 = 2.02 g H2 1 mol Cl2 = 70.90 g Cl2 2 molHCl = 72.92 g HCl Therefore, 2.02g H2 will react with 70.90g Cl2 to form 72.92g of HCl.

  39. Steps to Balancing Equations • Compare the numbers of atoms on each side of the equation • Start with the most complicated molecules FIRST! • Leave H and O until the end • Place COEFFICIENTS in front of the compound to try and balance the atoms • Check your answer to see if: - The numbers of atoms on both sides of the equation are now balanced. • Reduce if possible!!!!

  40. Steps to Balancing Equations ___ Al(s) + ___ Br2(l) ---> ___ Al2Br6(s) 2 3

  41. Practice Balancing Equations 2 __Al + __O2 __Al2O2 3 2 2 __ Fe + __Cl2 __ FeCl3 3 3 __Fe2O3 + __H2SO4 __Fe2(SO4)3 + __H2O

  42. Online Balancing Equations Click on picture above to go to the site!

  43. Balancing Equations ____C3H8(g) + _____ O2(g) ----> _____CO2(g) + _____ H2O(g) 5 3 4 2 11 ____B4H10(g) + _____ O2(g) ----> ___ B2O3(g) + _____ H2O(g) 4 2 10 5

  44. Write and balance the following:Calcium reacts with water to form calcium hydroxide and hydrogen gas. BELL RINGER

  45. Practice Write out the following chemical equation  Methane reacts with oxygen to produce carbon dioxide and water + O2 + H2O CO2 CH4 

  46. Practice Write out the following chemical equation  Hydrogen gas reacts in the presence of oxygen gas to explode and produce liquid water. + O2(g) H2(g)  H2O(l) + energy

  47. Popcorn Lab

  48. Popcorn Day 2

  49. Balance the following:Sodium phosphate + iron (III) oxide  sodium oxide + iron (III) phosphate BELL RINGER Na3PO4 + Fe2O3 ----> Na2O + FePO4 2 3 2

  50. Types of Reactions There are five types of chemical reactions we will talk about: • Synthesis reactions • Decomposition reactions • Combustion reactions • Single replacement reactions • Double Replacement reactions • You need to be able to identify the type of reaction and predict the product(s)

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