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Stoichiometry. Chapter 9, 10, & 11

Stoichiometry. Chapter 9, 10, & 11. Standard 3 Ms. Siddall. vocabulary. Compound Chemical formula Coefficient Stoichiometry Mole Molar mass Molar volume Avogadro’s number Standard temperature and pressure. Anatomy of a chemical formula.

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Stoichiometry. Chapter 9, 10, & 11

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  1. Stoichiometry.Chapter 9, 10, & 11 Standard 3 Ms. Siddall

  2. vocabulary • Compound • Chemical formula • Coefficient • Stoichiometry • Mole • Molar mass • Molar volume • Avogadro’s number • Standard temperature and pressure

  3. Anatomy of a chemical formula chemical formula: a combination of symbols and numbers that describe the amount and type of atoms that form a compound. CuSO4(aq) Example: • Atomic symbols describe the type of atoms in the compound • (copper, sulfur, oxygen) • subscript numbers describe the number of atoms in the compound • (1 copper, 1 sulfur, 4 oxygen) • physical state of the compound is described using subscript letters • (aq = aqueous)

  4. study question 1 Na2O(s) In the above formula: • How many sodium atoms? • How many oxygen atoms? • What is the physical state? • Is the compound ionic or covalent?

  5. Standard 3a: describing chemical reactions An equation describes a chemical reaction or a physical change • Reactants: chemicals that react • Products: chemicals that are formed • e.x. sodium + oxygen  sodium oxide Na(s) + O2(g) Na2O(s) reactants product

  6. study question 2 Pb(NO3)3(aq) + KI(aq) KNO3(aq) + PbI3(s) • Label the reactants and the products in the reaction above • Are the reactants and products covalent or ionic? • How many oxygen atoms are in the compound Pb(NO3)3?

  7. Symbols describing chemical reactions Copy table 11.1 (page 323) That’s right – open your book to page 323 and copy that table into your notes… go on… do it! This spot had better not be blank when I check your notebook!

  8. study question 3 • What do the following symbols mean? • (l) • (aq) •  • Pb(NO3)3(aq) + KI(aq) KNO3(aq) + PbI3(s) • Which compound is solid?

  9. Balancing chemical equations The Law of Conservation of Matter:Matter cannot be created or destroyed. • For chemical equations: The total number of each type of atom must be the same before and after the reaction Law: Thou shall not create or destroy matter

  10. example • Sodium reacts with oxygen to produce sodium oxide • How many sodium atoms react? • How many sodium atoms are in the product? • This violates the law of conservation of matter! Na(s) + O2(g) Na2O(s) 1 2

  11. study question 4 NaI(s) + Cl2(g) NaCl(s) + I2(s) • Count the number of atoms on the reactants side • Sodium ____ • Iodine ____ • Chlorine ____ • Count the number of atoms on the products side • Sodium ____ • Iodine ____ • Chlorine ____ Does this equation obey the law of conservation of matter?

  12. Example: Na(s) + O2(g) Na2O(s) 4 2 • Coefficients are used to balance the equation • number of atoms or formulas needed in the reaction. These apply to the entire formula (all the atoms) • 4Na = 4 sodium atoms • 2Na2O = 4 sodium atoms and 2 oxygen atoms SUBSCRIPTS CAN NOT CHANGE!

  13. study question 5 2Cu(s) + O2(g) 2CuO(s) • Count the number of atoms on the reactants side • copper ____ • Oxygen ____ • Count the number of atoms on the products side • copper ____ • Oxygen ____ Does this equation obey the law of conservation of matter?

  14. Rules of Balancing Equations • Write the equation using correct formulas. You may NOT change the formula in any way. • Balance the equation using coefficients

  15. Balancing example: sodium and oxygen react to form sodium oxide Take atomic inventory: (you mustobey the Law of Conservation of Matter) Na + O2 Na2O Reactants: Products: Na O Na O 1 2 2 1 Problem: begin with 2 oxygen atoms but end with only 1 This breaks the law of conservation of matter.

  16. Na + O2 Na2O 2 (= Na2O + Na2O) solution: Add the coefficient ‘2’ in front of Na2O Take atomic inventory again: Reactants: Products: Na O Na O 1 2 4 2 Problem: begin with 1 sodium atom but end with 4. This breaks the law of conservation of matter.

  17. 4 Na + O2 2Na2O solution: Add the coefficient ‘4’ in front of Na Take atomic inventory again: Reactants: Products: Na O Na O 4 2 4 2 4 sodium atoms combine with 1 oxygen molecule to form 2 formula units of sodium oxide. This equation obeys the Law of Conservation of Matter.

  18. study question 6 • BALANCE THE FOLLOWING REACTION: H2(g) + O2(g) H2O(l)

  19. Balancing with polyatomic ions • Sometimes polyatomic ions break apart in a chemical reaction and sometimes they do not • e.x. sulfate appears on both sides of the reaction so SO4 can be treated like one atom: Mg(s) + CuSO4(aq) MgSO4(aq) + Cu(s) • e.x. carbonate breaks apart so atoms must be balanced individually: CaCO3(aq) + HCl(aq)  CaCl2(aq) + H2O(l) + CO2(g)

  20. study question 7 • Balance the following equations: • Na2CO3(s) + HCl(aq) NaCl(aq) + CO2(g) + H2O(l) • K2SO4(aq) + CaCl2(aq) CaSO4(s) + KCl(l)

  21. Types of Chemical Reactions. 1. Combination. • Also called synthesis • Two or more reactants combine to form one product • e.x. 2 Na(s) + Cl2(g) 2 NaCl(s) • A + B  AB

  22. study question 8 Which equation represents a synthesis reaction? • 2Ca(s) + O2(g) 2CaO(s) • 2KClO3(s)  2KCl(s) +O2(g)

  23. 2. Decomposition. • One reactant decomposes to form two or more products. • 2H2O(l) 2H2(g) + O2(g) • AB  A + B

  24. study question 9 Which equation represents a decomposition reaction? • Ca(s) + O2(g) CaO(s) • 2KClO3(s)  2KCl(s) +O2(g)

  25. 3. Single Replacement. • An atom replaces an ion in a compound. • Mg(s) + CuSO4(aq) MgSO4(aq) + Cu(s) • Cl2(g) + 2KI(aq)  I2(s) + 2KCl(aq) • A + BC  AC + B

  26. study question 10 Which equation represents a single replacement reaction? • 2NaI(s) + Cl2(g) 2NaCl(s) + I2(s) • 2NaI(aq) + Pb(NO3)2(aq) 2NaNO3(aq) + PbI2(s)

  27. 4. Double Replacement. • Ions from different compounds switch places. • CaCO3(s) + 2HCl(aq) CaCl2(s) + H2CO3(aq) • AB + CD AD + CB

  28. study question 11 Which equation represents a double replacement reaction? • 2NaI(s) + Cl2(g) 2NaCl(s) + I2(s) • 2NaI(aq) + Pb(NO3)2(aq) 2NaNO3(aq) + PbI2(s)

  29. 5. Combustion reactions. • A compound reacts with oxygen • often produces CO2 & H2O • e.x. C3H8(g) + 5O2(g) 3CO2(g) + 4H2O(g) • Note: a combustion reaction can also be a decomposition or a combination reaction

  30. study question 12 • Write the balanced equation for the reaction of CO with O2 to form CO2 and identify the type of reaction.

  31. Standard 3e:The Arithmetic of Equations. • A balanced equation shows the amount of each reactant and product needed or produced in any reaction.

  32. Example. • Mg(s) + 2HCl(aq) MgCl2(aq) + H2(g) • One atom of magnesium combines with 2 formula units of HCl to form one formula unit of magnesium chloride and one molecule of hydrogen gas. • Use equation coefficients to solve quantitative problems.

  33. study question 13 4Na(s) + O2(g) 2Na2O(s) • How many molecules of oxygen are needed to react with 4 atoms of sodium? • How many oxygen atoms is that? • How many formula units of sodium oxide are produced when 4 atoms of sodium are used?

  34. Example. • Mg(s) + 2HCl(aq) MgCl2(aq) + H2(g) • If 1 atom of magnesium is used, 2 formula units of HCl are needed to react. • If 6 atoms of magnesium are used, how many formula units of HCl are needed? 6 atom Mg Fo.U. HCl 2 Fo.U. HCl 12 = 1 atom Mg

  35. Anatomy of a conversion T-Chart: multiply everything on top and divide by everything on the bottom Units for answer Given(units) = answer Units of given What you know What you get Conversion factor

  36. study question 14 Mg(s) + 2HCl(aq) MgCl2(aq) + H2(g) • if 4 molecules of H2 are created • how many Fo.U. of HCl are needed? • How many atoms of Mg are used?

  37. Standard 3b: The Mole Atoms and molecules are so small scientists must use a large number of atoms, molecules or formula units in order to observe chemical reactions. This large number is called: A Mole

  38. Standard 3c: Avogadro’s Number The number of particles in one mole= Avogadro’s number = 6.02 x 1023 = 602,000,000,000,000,000,000,000 Particles = atoms, molecules, formula units, donuts…

  39. study question 15 • How many dollars would you have if you had Avogadro’s number of dollars?

  40. Avogadro’s number is convenient because a mole of any chemical is easily measured in the laboratory. • Instead of using 6.02 x 1023 atoms we use 1 mole of atoms.

  41. study question 16 4Na(s) + O2(g) 2Na2O(s) • How many moles of O2 are needed to react with 4 moles of sodium? • How many moles of O2 are needed to react with 2 moles of sodium? • How many moles of Na2O are produced when 2 moles of sodium are used?

  42. particles volume Standard 3e: stoichiometry 6.02x1023 particles 1 mole 1 mole 22.4L 1 mole 6.02x1023 particles 22.4L 1 mole Moles Moles coefficients 1 mole Molar mass(g) Molar mass(g) 1 mole mass

  43. 1 Mole of any atom has a mass (in grams) numerically equivalent to the mass of a single atom (in amu). This mass is displayed on the periodic table.

  44. study question 17 • What is the mass of one mole of: • Aluminum? • Carbon?

  45. Standard 3d: Molar Mass= the mass of one mole of any substance. • Example: Na2O Sodium = 23g/mole Oxygen = 16g/mole 1 mole Na2O: (2x23g/mole) + 16g/mole = The molar mass for Na2O = 62g/mole

  46. study question 18 • calculate the molar mass of AlCl3 (don’t forget units!)

  47. examples Molar mass! • What is the mass of 3 moles of sodium hydroxide? 3 moles NaOH 40 g NaOH = 120 g NaOH 1 mole NaOH • How many moles of carbon dioxide are in a sample weighing 88g? 88g CO2 1 mole CO2 = 2 moles CO2 44g CO2

  48. study question 19 A person produces just less than 0.5 moles CH4 per day. How many grams is that?

  49. The volume of a Mole 1 mole of any GAS has a volume of 22.4L at standard temperature and pressure • Standard temperature = 0°C • Standard pressure = 1atm

  50. study question 20 • What is the volume of 2 moles of gas? • What is the volume of 0.5 moles of gas? (At standard temperature and pressure)

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