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Friday, April 15 th : “A” Day Monday, April 18 th : “B” Day Agenda

Friday, April 15 th : “A” Day Monday, April 18 th : “B” Day Agenda. Homework Problems/Questions Finish Section 7.3 (we’re almost done…) In-Class: Section 7.3 review, pg. 248: #1-7 (6,7 abc ONLY) Concept Review: “Formulas and Percentage Composition”: #11-15

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Friday, April 15 th : “A” Day Monday, April 18 th : “B” Day Agenda

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  1. Friday, April 15th: “A” DayMonday, April 18th: “B” DayAgenda • Homework Problems/Questions • Finish Section 7.3 (we’re almost done…) • In-Class: • Section 7.3 review, pg. 248: #1-7 (6,7 abc ONLY) • Concept Review: “Formulas and Percentage Composition”: #11-15 • Quiz over section 7.3 (last ½ hour) Next time: ACT sample science test Lab Write-Up

  2. Chemical Formulas can give Percentage Composition • If you know the chemical formula of any compound, you can calculate the percentage composition. • From the subscripts, determine the mass contributed by each element and add these to get molar mass. • Divide the mass of each element by the molar mass. • Multiply by 100 to find the percentage composition of that element.

  3. CO and CO2 are both made up of C and O, but they have different percentage compositions.

  4. Using a Chemical Formula to Determine Percentage Composition(Sample Problem I, pg. 247) Calculate the percentage composition of copper (I) sulfide. • The formula for copper (I) sulfide is: Cu2S • because copper is 1+ and the sulfide ion is 2-

  5. Sample Problem I, continued… • Find the molar mass of Cu2S: • Cu = 2 (63.55 g/mol) = 127.1 g/mol • S = 32.07 g/mol Molar mass of Cu2S: 159.17 g/mol

  6. Sample Problem I, continued… 2. Divide the mass of each element in the compound by the molar mass of the compound. 3. Then multiply by 100% to get the % composition. For Cu = 2 (63.55) X 100% = 79.85 % 159.17 For S = 32.07 X 100% = 20.15% 159.17 • Check your work, when added together, the sum should be near 100%

  7. Additional Practice Determine the percentage composition of H2SO3. • Find molar mass of H2SO3. • H: 2 (1.01 g/mol) = 2.02 g/mol • S: 32.07 g/mol • O: 3 (16.00 g/mol) = 48.00 g/mol Molar mass of H2SO3 = 82.09 g/mol

  8. Additional Practice 2. Divide the mass of each element in the compound by the molar mass of the compound. • Then multiply by 100% to get the % composition For H = 2 (1.01) X 100% = 2.46% 82.09 For S = 32.07 X 100% = 39.07% 82.09 For O = 3 (16.00) X 100% = 58.47% 82.09

  9. In-Class Assignments • Section 7.3 review, pg. 248: #1-7 (6,7 a,b,c ONLY) • Concept Review: “Formulas and Percentage Composition”: #11-15

  10. Section 7.3 Quiz“Formulas and Percentage Composition” • Use your guided notes and your book to complete this quiz on your own…

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