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The Mole 1 dozen = 12 1 gross = 144 1 ream = 500 1 mole = 6.02 x 1023

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**I didn’t discover it. Its just named after me!**

Avogadro’s Number 6.02 x 1023 is called “Avogadro’s Number” in honor of the Italian chemist Amadeo Avogadro ( ). I didn’t discover it. Its just named after me! Amadeo Avogadro

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**Calculations with Moles: Using Avogadro’s Number**

How many atoms of lithium are in 3.50 moles of lithium? 3.50 mol Li 6.02 x 1023 atoms Li = atoms Li 2.11 x 1024 mol Li

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Review: Molar Mass A substance’s molar mass (molecular weight) is the mass in grams of one mole of the compound. CO2 = grams per mole H2O = grams per mole Ca(OH)2 = g/mol

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Page 296, #s 7-8 PCl3

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**Calculations with Moles: Converting moles to grams**

How many grams of lithium are in 3.50 moles of lithium? 3.50 mol Li 7.0 g Li = g Li 25 mol Li

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**Calculations with Moles: Converting grams to moles**

How many moles of lithium are in 18.2 grams of lithium? 18.2 g Li mol Li = mol Li 2.6 7.0 g Li

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**Calculations with Moles: Using Avogadro’s Number**

How many atoms of lithium are in 18.2 g of lithium? 18.2 g Li mol Li 6.02 x 1023 atoms Li 7.0 g Li mol Li (18.2)(6.02 x 1023)/7.0 = atoms Li 1.6 x 1024

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Standard Molar Volume Equal volumes of all gases at the same temperature and pressure contain the same number of molecules. - Amedeo Avogadro

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Standard Molar Volume

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**Standard Temperature and Pressure “STP”**

P = 1 atmosphere, kPa T = 0°C, 273 Kelvins The molar volume of an ideal gas is 22.4 liters at STP

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**Calculating Percentage Composition**

Calculate the percentage composition of magnesium carbonate, MgCO3. 24.0 g g + 3(16.0 g) = 84.0 g 100.00

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**Formulas molecular formula = (empirical formula)n [n = integer]**

Empirical formula: the lowest whole number ratio of atoms in a compound. Molecular formula: the true number of atoms of each element in the formula of a compound. molecular formula = (empirical formula)n [n = integer] molecular formula = C6H6 = (CH)6 empirical formula = CH

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Formulas (continued) Formulas for ionic compounds are ALWAYS empirical (lowest whole number ratio). Examples: NaCl MgCl2 Al2(SO4)3 K2CO3

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Formulas (continued) Formulas for molecular compounds MIGHT be empirical (lowest whole number ratio). Molecular: H2O C6H12O6 C12H22O11 Empirical: H2O CH2O C12H22O11

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**Empirical Formula Determination**

Base calculation on 100 grams of compound. Determine moles of each element in 100 grams of compound. Divide each value of moles by the smallest of the values. Multiply each number by an integer to obtain all whole numbers.

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**Empirical Formula Determination**

Adipic acid contains 49.32% C, 43.84% O, and 6.85% H by mass. What is the empirical formula of adipic acid?

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**Empirical Formula Determination (part 2)**

Divide each value of moles by the smallest of the values. Carbon: Hydrogen: Oxygen:

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**Empirical Formula Determination (part 3)**

Multiply each number by an integer to obtain all whole numbers. Carbon: 1.50 Hydrogen: 2.50 Oxygen: 1.00 x 2 x 2 x 2 3 5 2 Empirical formula: C3H5O2

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**Finding the Molecular Formula**

The empirical formula for adipic acid is C3H5O2. The molecular mass of adipic acid is 146 g/mol. What is the molecular formula of adipic acid? 1. Find the formula mass of C3H5O2 3(12.0 g) + 5(1.0) + 2(16.0) = 73.0 g

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**Finding the Molecular Formula**

The empirical formula for adipic acid is C3H5O2. The molecular mass of adipic acid is 146 g/mol. What is the molecular formula of adipic acid? 3. Multiply the empirical formula by this number to get the molecular formula. 3(12.0 g) + 5(1.0) + 2(16.0) = 73.0 g (C3H5O2) x 2 = C6H10O4

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