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Chapter 3

Chapter 3. Matter-Properties and Changes. Outline Chapter 3 Be sure to include all vocab words. Law of Definite Proportions. The law states that regardless of the amount, a compound is always composed of the same elements in the same proportion by mass.

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Chapter 3

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  1. Chapter 3 Matter-Properties and Changes

  2. Outline Chapter 3 • Be sure to include all vocab words

  3. Law of Definite Proportions • The law states that regardless of the amount, a compound is always composed of the same elements in the same proportion by mass. • Percent by mass (Percent composition) • Shows the ratio of the mass of each element to the total mass of the compound as a percentage • Percent by mass = mass of element / mass of compound x 100

  4. Percent composition • Percent by mass of every element involved

  5. Ex. Pg 75 • Practice problems pg. 76 #20-24

  6. Law of Multiple Proportions • The law states that when different compounds are formed by a combination of the same elements, different masses of one element combine with the same relative mass of the other element in a ratio of small whole numbers.

  7. Law of Multiple Proportions • Cu+1 + Cl-1 = CuCl • Cu+2 + Cl-1 = CuCl2 • Quick lesson • What type of bond is this? • Ionic – opposite charges attract • Does the subscript 2 mean that the chlorine atoms are combined? • No (Show why) • + - - or - + - • Why does this type of reaction occur? • Metals tend to lose electrons but they can lose different numbers of electrons

  8. Law of Multiple Proportions • Cu+1 + Cl-1 = CuCl • Cu+2 + Cl-1 = CuCl2 • Use table 3-6 • Calculate the ratio of Cl per fixed mass of Cu. • What if you are only given %? • Always use a total of 100 g. • What if you are given mass? • Don’t worry about doing percentages • Always put the biggest number on top when getting whole number ratio.

  9. You have 100 g of CuCl and 40 g of CuCl. • What law is shown when the percent composition is calculated? • You have 10 g of C and 20 g of O in compound I. You have 10 g of C and 10 g of O in compound II. Calculate the ratio of O per fixed mass of C. • What law is shown when the ratio is calculated?

  10. Practice problem pg 77 #30

  11. Homework • Pg 83 60-69

  12. Math • x/y ÷ a/b = xb/ya

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