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Chemical Formulas and Chemical Compounds

Chemical Formulas and Chemical Compounds. Using Chemical Formulas. Definitions:. Formula Mass : sum of the atomic masses of all the atoms in a molecule or formula unit; measured in amu Example: H 2 O For water this can also be called the Molecular Mass. Definitions.

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Chemical Formulas and Chemical Compounds

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  1. Chemical Formulas and Chemical Compounds Using Chemical Formulas

  2. Definitions: Formula Mass: sum of the atomic masses of all the atoms in a molecule or formula unit; measured in amu Example: H2O For water this can also be called the Molecular Mass

  3. Definitions Molar Mass – the mass of one mole of a substance; numerically equal to the formula mass; measure in g/mol • The formula mass of H2O is 18.0153 amu • The molar mass of H2O is 18.0153 g/mol

  4. Sample Problems • What is the mass in grams of 3.04 moles of ammonia vapor, NH3? • Calculate the mass of 0.257 moles of calcium nitrate. • The odor of bananas is due to the compound isopentyl acetate, C7H14O2. How many moles of isopentyl acetate are present in a 5.0 gram sample of the compound? • When bees sting, they also release the compound isopentyl acetate. How many molecules of the compound are there in 2.00 grams?

  5. Sample Problems • Dioxin, C12H4Cl4O2, is an extremely toxic substance. How many moles of dioxin are there in 700.0 grams of the substance? • One type of antibiotic, penicillin F, has the formula C14H20N2SO4. How many molecules of penicillin are there in a 250.0 mg dose.

  6. Class Warmup - Part 1 Consider a sample of 10.0 g of the gaseous hydrocarbon C3H4 . How many molecules are present in the sample?

  7. Class Warmup - Part 2 • Express each of the following as a decimal # a. 56 % b. 0.592 % • Express each of the following as a percentage. a. 0.10 b. 3 cm3/4 cm3 • If you lost 25 marbles and found only 10, what percentage of the marbles did you find? What percentage is still lost? • A 59 g mixture contains 23 g of glucose. What is the percentage of glucose in the mixture?

  8. Percentage Compositon Percentage Composition – the percentage by mass of each element in a compound Remember: According to the law of constant composition the percentage composition for a compound is always exactly the same.

  9. Percentage Composition Example: TNT - 2, 4, 6 trinitrotoluene C – 37.017% H – 2.21883 % N – 18.5002 % O – 42.2644 %

  10. Sample Problems • Calculate the percentage composition of sodium nitrate. • What is the mass percentage of water in the hydrate, CuSO4.5H2O? • Zinc chloride, ZnCl2 is 52.02 % chlorine a. What mass of chlorine is contained in 80.3 g of ZnCl2? b. How many moles of Cl is this?

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