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Chemical Quantities

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**Describe the concept of the mole and its importance to measurement in chemistry.**

Calculate the mass of compounds in atomic mass units. Calculate the molar mass of various substances. Additional KEY Terms Avogadro’s number

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**Particles are now counted in moles (n).**

Avogadro ( ) Any sample of any gas at the same temperature and pressure will contain the same number of particles. Defined 22.4 L as the molar volume for any gas. Particles are now counted in moles (n).

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**The mass of 1 mole is the molar mass - (g/mol)**

One mole of any particle has a mass equal to its total formula mass – IN GRAMS. The mass of 1 atom of Al = 27.0 µ The mass of 1 mole of Al atoms = 27.0 g The molecular mass of water (H2O) is 18.0 µ ... So...the molar mass of water is 18.0 g/mol.

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**What is the molar mass of ammonium dichromate?**

(NH4)2Cr2O7 Determine the molar mass. 1 mole of (NH4)2Cr2O7 = 2 N + 8 H + 2 Cr + 7 O = 2(14.0g/mol)+ 8(1.0g/mol)+ 2(52.0g/mol)+ 7(16.0g/mol) (NH4)2Cr2O7 = g/mol

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**And Dimensional Analysis**

Mole Questions And Dimensional Analysis

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**Rules for using a Dimensional Analysis**

1. Start with what you know 2. Put ratio units you want to cancel on bottom 3. Put ratio units you need on the top 4. Multiply across the top, Divide across the bottom How many pizzas would 250 pieces of pepperoni make? 250 pepperoni 1 slice 1 pizza = 7.8 Pizzas 4 pepperoni 8 slice

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**154.0 g 1 mole 154.0 g 1 mole or 1.20 x 10-5 mol 1 mol 154.0 g**

What is the mass of 1.20 x 10–5 moles of carbon tetrachloride, CCl4? CCl4 = 1 C + 4 Cl = 1(12.0 g/mol) + 4(35.5 g/mol) = g/mol 154.0 g 1 mole 154.0 g 1 mole or 1.20 x 10-5 mol 1 mol 154.0 g 1.85 x 10-3 g

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**Calculating the Number of Particles**

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**In one mole there is 6.02 x 1023 particles.**

We call this - Avogadro's Number 6.02 x particles 1 mole The term "particle" refers to any individual thing like atoms, formula units, molecules, ions, etc. 6.02 x particles 1 mole or 6.02 x pencils is 1 mole of pencils 6.02 x carbon atoms is 1 mole… 6.02 x water molecules is 1 mole…

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**= = 1 mole 1 mole How many atoms in 25.0 moles of copper?**

25.0 mol Cu 6.02 x particles = 1.51 x atoms 1 mole How many molecules of water in 1.50 x 10–5 moles? 6.02 x particles 1.50 x 10–5 mol H2O = 9.03 x 10 18 molecules of water 1 mole

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**= How many moles is 5 atoms of zinc? 1 mole 8.31 x 10-24 moles**

5 atoms Zn 1 mole = 8.31 x moles 6.02 x particles 5 atoms of Zinc is 8.31 x 10–24 moles.

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**The mole allows the conversion between mass and number of particles.**

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**= = 0.556 mol H20 3.34 x 10 23 molecules H20 1 mole 1 mole 18.0 g**

How many molecules of water in a 10.0 g sample of water? 10.0 g H2O 1 mole = 0.556 mol H20 18.0 g 0.556 mol H2O 6.02 x particles 1 mole = 3.34 x molecules H20

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**Put the two equations together**

10.0 g H2O 1 mole 6.02 x particles of H2O 18.0 g 1 mole = 3.34 x molecules H20 There are 3.34 x 1023 molecules in 10.0 g of water.

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**= 5.14 x 10 23 atoms 1 mole 2 atoms 1 For. U**

How many atoms in 25.0 g of sodium chloride? NaCl = 58.5 g/mol 1 mole 6.02 x For.U 25.0 g NaCl 58.5 g 2 atoms 1 For. U = 5.14 x atoms

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CAN YOU / HAVE YOU? Describe the concept of the mole and its importance to measurement in chemistry. Calculate the mass of compounds in atomic mass units. Calculate the molar mass of various substances. Additional KEY Terms Avogadro’s number

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