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Lab 8 Gravimetric analysis of salt

Lab 8 Gravimetric analysis of salt. Concepts % composition. A. Percentage Composition. the percentage by mass of each element in a compound. 28 g 36 g. 8.0 g 36 g. A. Percentage Composition. Find the percentage composition of a sample that is 28 g Fe and 8.0 g O.  100 =. 78% Fe.

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Lab 8 Gravimetric analysis of salt

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  1. Lab 8Gravimetric analysis of salt Concepts • % composition

  2. A. Percentage Composition • the percentage by mass of each element in a compound

  3. 28 g 36 g 8.0 g 36 g A. Percentage Composition • Find the percentage composition of a sample that is 28 g Fe and 8.0 g O.  100 = 78% Fe %Fe =  100 = 22% O %O =

  4. 127.10 g Cu 159.17 g Cu2S 32.07 g S 159.17 g Cu2S A. Percentage Composition • Find the % composition of Cu2S.  100 = %Cu = 79.852% Cu %S =  100 = 20.15% S

  5. A. Percentage Composition • How many grams of copper are in a 38.0-gram sample of Cu2S? =79.852% Cu Cu2S is (38.0 g Cu2S)(0.79852) = 30.3 g Cu

  6. 36.04 g 147.02 g A. Percentage Composition • Find the mass percentage of water in calcium chloride dihydrate, CaCl2•2H2O? 24.51% H2O %H2O =  100 =

  7. A. Percentage Composition • How many grams of calcium chloride, are in a 200.0-gram sample of CaCl2•2H2O ? CaCl2 is 75.49% of CaCl2•2H2O (200.0 g Cu2S)(0.7549) = 150.98 gCaCl2

  8. Procedures • Read pg 79 and follow all the procedures • Weigh approx 0.3g of a unknown solid • Add 20 ml of a 0.5M AgNO3 • Collect the precipitate (AgCl)

  9. Procedures • Only do one trial, and get results from 2 other lab groups

  10. Procedures • Weigh approx 0.3g of a unknown solid • Transfer to a 250 ml beaker • Add 150 ml water and 1 ml of 6M HNO3 • Warning HNO3 is corrosive!! • Stir with a glass rod

  11. Step 2Procedures • Add 20 ml of a 0.5M AgNO3 to a 250 ml beaker • Warm slowly on a hot plate for 8 minutes • Do Not boil!!!

  12. Step 3Procedures • Obtain and weigh filter paper • Fold paper as illustrated in diagram 8.1 • Place into glass funnel, and wet paper with distilled water • Transfer precipitate (AgCl), to filter paper • Follow procedures on page 80 carefully

  13. Step 4Procedures • Carefully remove precipitate (AgCl),and filter paper and place on watch glass • Place precipitate (AgCl), filter paper and watch glass in oven for twenty minutes • Determine mass of AgCl,

  14. Step 5Procedures • Determine % composition of Chlorine in silver Chloride

  15. Standard Deviation •  Is the square root of the average of the squares of the deviations when all answers are given as positive signs. • Objective: find std deviation of % chloride • see pgs 80-81

  16. Finding the Standard Deviation • S = √ | xi – μ |2 (n-1)

  17. Finding the Standard Deviation • S = Standard Deviation • n = number of trials •  = sum • µ = Average of the % chlorides • xi = Each individual % • | |2 = The Square of the Absolute value (Always give positive answer) • Report Answer as x  S

  18. What is Due Next week • Pg 85 and 86 • Read up on lab 12

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