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**Chapter 10 “Chemical Quantities”**

Yes, you will need a calculator for this chapter!

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**Section 10.1 Da Mole: A Measurement of Matter**

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How do we measure items? Measure mass in grams. Measure volume in liters. Measure amount in MOLES.

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**We’re not talking about this kind of mole!**

What is the mole? We’re not talking about this kind of mole!

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**Moles (mol) It is an amount.**

Defined as the number of carbon atoms in exactly 12 grams of carbon-12. 1 mole = 6.02 x of representative particles. 6.02 x 1023 is called: Avogadro’s number. 1 mole = 6.02 x 1023 = Avogadro’s number

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**Similar Words for amount**

Dozen: Mole: 1 dozen muffins = 12 muffins 1 mol muffins = x 1023 muffins 2 dozen puppies = 24 puppies 2 mol puppies = 1.2 x 1024 puppies 36 m&m stuffed donuts = 3 dozen donuts 2.4 x 1024 m&m stuffed donuts = 4 mol donuts

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**What are Representative Particles?**

The smallest pieces of a substance: Changes based on what we’re looking at For a molecular compound: it is the molecule. For an ionic compound: it is the formula unit (ex: NaCl, MgS). For an element: it is the atom. 1 mol of CO2 molecules, 1 mol of NaCl formula units, and 1 mol of H atoms all equal 6.02 x 1023 of that thing. Remember the 7 diatomic elements? (made of molecules)

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Measuring Moles The atomic mass on the PT is also the molar mass (g/mol) – mass (in grams) of 1 mole of that atom = 16.0 g/mol Since the mole is the number of atoms in 12 grams of carbon-12, Gram atomic mass (GAM)- Equals the mass of 1 mole of an element in grams (from periodic table) 12.01 grams of C has the same number of pieces as 1.01 grams of H and grams of Fe. We can write this as: 12.01 g C = 1 mole C (this is also the molar mass) (**Remember we can count things by weighing them.)

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**Find the Molar Mass (g/mol) of the following:**

Nitrogen Aluminum Zinc 14.01 g/mol 26.98 g/mol 65.39 g/mol

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**What about compound mass?**

In 1 mole of H2O, there are 2 moles of H atoms and 1 mole of O atoms To find the mass of a compound: Determine number of each element present Multiply the number times their mass (from the periodic table) Add them up for the total mass

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**Calculating Compound Mass**

Calculate the mass of magnesium carbonate, MgCO3. 24.31 g/mol g/mol x (16.00 g/mol) = 84.32 g/mol MgCO3

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**Practice Problem: What is the mass of one mole of CH4?**

1 mole of C = g/mol 4 mole of H x 1.01 g = 4.04g/mol 1 mole CH4 = = g/mol 12

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**Mole Practice 1 mol = particles 2.5 mol MgCl2 = ? particles MgCl2 =**

x 1024 Fe particles = ? mol Fe 2.5 mol 6.02 x 1023 particles 1.5 x 1024 particles of MgCl2 1 mol 7.2 x 1024 particles 1 mol 12 mol Fe 6.02 x particles

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**Molar Mass Practice 47 g/mol 180 g/mol 4. Molar mass of BeF2 =**

5. Molar mass of C6H12O6 = Be = 9.0 g/mol (19.0) = 47 g/mol F = 19.0 g/mol C = 12.0 g/mol 6(12.0) + 12(1.0) + 6(16.0) = H = 1.0 g/mol 180 g/mol O= 16.0 g/mol

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**Section 10.2 Mole-Mass and Mole-Volume Relationships**

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**Use to make conversion factors from these. **

Since Molar Mass is… Number of grams in 1 mole. grams per mole (g/mol) Use to make conversion factors from these. - Use molar mass to convert to grams or mols of a substance.

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**For example How many moles is 5.69 g of NaOH? =**

How many grams in .53 mol of NaOH? .142 mol NaOH 1 mol NaOH 5.69 g NaOH 40.0 g NaOH 40.0 g NaOH 21.2 g NaOH .53 mol NaOH 1 mol NaOH 17

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**28.1 grams C 1.000 mol Mg Practice Problems:**

How much would 2.34 moles of carbon weigh? How many moles of magnesium is g of Mg? 28.1 grams C 1.000 mol Mg

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**The Mole-Volume Relationship**

Under different circumstances, gases can change. Two things effect the volume of a gas: a) Temperature and b) Pressure **We need to compare all gases at the same temperature and pressure.

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**Standard Temperature and Pressure**

abbreviated STP 0ºC (273K) and 1.0 atm pressure At STP 1 mole of gas occupies L= molar volume 22.4 L/mol of any gas at STP 20

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**Practice Problems: = 0.253 mol O2**

What is the volume of 4.59 mole of CO2 gas at STP? How many moles is L of O2 at STP? 4.59 mol CO2 22.4 L CO2 = 103 L CO2 1 mol CO2 5.67 L O2 1 mol O2 = mol O2 22.4 L O2

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**12.3 L CH4 22.4 L CH4 8.8 g CH4 1 mol CH4 16.0 g CH4 1 mol CH4**

What is the volume of 8.8 g of CH4 gas at STP? = 22.4 L CH4 8.8 g CH4 1 mol CH4 16.0 g CH4 1 mol CH4 12.3 L CH4

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**Summary: These four items are all equal: a) 1 mole**

b) molar mass (in grams/mol) c) 6.02 x 1023 particles (atoms, molecules, or formula units) d) 22.4 L of a gas at STP **Thus, we can make conversion factors from them.

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**Avog. # Practice problems:**

How many molecules of CO2 are in 4.6 moles of CO2? How many moles of water is in 5.87 x molecules? How many atoms of carbon are in moles of Carbon? How many moles is 7.78 x 1024 formula units of MgCl2? 2.8 x 1024 molecules of CO2 mol H2O (or 9.75 x 10-2) 7.405 x 1023 atoms C 12.9 moles MgCl2

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**Mixed Practice Problems:**

How many atoms of lithium is 1.0 g of Li? How much would 3.45 x 1022 atoms of U weigh? What is the volume of 10.0 g of CH4 gas at STP? 8.7 x 1022 atoms Li 13.6 g U 14.0 L CH4

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**Section 10.3 Percent Composition and Chemical Formulas**

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**Percentage Composition**

Percentage by mass of each element in a compound

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**Calculating Percent Composition of a Compound**

Like all percent problems: part whole Find mass of each element (from the periodic table) Next, divide by total mass of compound; then x 100 x 100 % = percent

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**Percentage Composition**

Find the % composition of Cu2S. g Cu g Cu2S %Cu = 100 = 79.85% Cu 32.07 g S g Cu2S %S = 100 = 20.15% S

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**Percentage Composition**

Find the mass percentage of water in calcium chloride dihydrate, CaCl2•2H2O? 36.04 g g %H2O = 100 = 24.51% H2O

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**Empirical Formula (EF)**

Lowest whole number ratio of atoms in a compound C2H6 simplify subscripts CH3

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**Empirical Formula (EF)**

Just find lowest whole number ratio C6H12O6 CH4N Formula is not just ratio of atoms, it is also ratio of moles. In 1 mole of CO2 there is 1 mole of carbon and 2 moles of oxygen. In one molecule of CO2 there is 1 atom of C and 2 atoms of O. = CH2O = this is already the lowest ratio.

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Formulas (continued) Formulas for ionic compounds are ALWAYS empirical (the lowest whole number ratio = cannot be reduced). *Remember, we simplify beforehand 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 (Correct formula) Empirical: H2O CH2O C12H22O11 (Lowest whole number ratio)

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Formulas Empirical Formula (EF) = lowest whole number ratio of elements in a compound. Molecular Formula (MF) = the actual ratio of elements in a compound. The two can be the same. CH2 = C2H4 = C3H6 = H2O = H2O is also MF EF MF MF EF 35

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**Last extra practice slide**

How many O atoms are in 5 mol of Al2O3? How many Al atoms are in 5 mol of Al2O3? mol O 6.02e23 atoms O 5 mol Al2O3 3 1 mol Al2O3 1 mol O 9.03e24 atoms O 5 mol Al2O3 2 mol Al 6.02e23 atoms Al 1 mol Al2O3 1 mol Al 6.02e24 atoms Al

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