Chemical Formulas and Chemical Compounds Using Chemical Formulas.

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Presentation transcript:

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 Molar Mass – the mass of one mole of a substance; numerically equal to the formula mass; measure in g/mol The formula mass of H 2 O is amu The molar mass of H 2 O is g/mol

Sample Problems 1.What is the mass in grams of 3.04 moles of ammonia vapor, NH 3 ? 2.Calculate the mass of moles of calcium nitrate. 3.The odor of bananas is due to the compound isopentyl acetate, C 7 H 14 O 2. How many moles of isopentyl acetate are present in a 5.0 gram sample of the compound? 4.When bees sting, they also release the compound isopentyl acetate. How many molecules of the compound are there in 2.00 grams?

Sample Problems 5.Dioxin, C 12 H 4 Cl 4 O 2, is an extremely toxic substance. How many moles of dioxin are there in grams of the substance? 6.One type of antibiotic, penicillin F, has the formula C 14 H 20 N 2 SO 4. How many molecules of penicillin are there in a mg dose.

Class Warmup - Part 1 Consider a sample of 10.0 g of the gaseous hydrocarbon C 3 H 4. How many molecules are present in the sample?

Class Warmup - Part 2 1.Express each of the following as a decimal # a. 56 % b % 2.Express each of the following as a percentage. a b. 3 cm 3 /4 cm 3 3.If you lost 25 marbles and found only 10, what percentage of the marbles did you find? What percentage is still lost? 4.A 59 g mixture contains 23 g of glucose. What is the percentage of glucose in the mixture?

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.

Percentage Composition Example: TNT - 2, 4, 6 trinitrotoluene C – % H – % N – % O – %

Sample Problems 1.Calculate the percentage composition of sodium nitrate. 2.What is the mass percentage of water in the hydrate, CuSO 4. 5H 2 O? 3.Zinc chloride, ZnCl 2 is % chlorine a. What mass of chlorine is contained in 80.3 g of ZnCl 2 ? b. How many moles of Cl is this?