4/5/16 Today I will explain the mole and use it in calculations Warm Up What is a dozen?

Chapter 10 -The Mole

In chemistry, we often use the term “the mole”!

The Mole Mole - The number of atoms of an element equal to the number of atoms in exactly 12.0 g of carbon-12. How many atoms is that?????

There are 602,000,000,000,000,000,000,000 atoms in this sample! The Mole There are 602,000,000,000,000,000,000,000 atoms in this sample!

1 mole = 6.02 x 1023 A counting number The Mole 12 2 144 Dozen = ? Pair = ? Gross = ? 12 2 144 1 mole = 6.02 x 1023

Elements Avogadro’s Number Ionic Compounds Formula units In chemistry, we use avogadro’s number as the number of atoms, molecules, formula units, ions, etc. in a mole!!! (Particles) Ionic Compounds Formula units Covalent Compounds Molecules Elements Atoms

1 mole of any element = 6.02 x 10 23 particles The Mole 1 mole of any element = 6.02 x 10 23 particles Avogadro’s number! Examples: 1mol C = 6.02 x 10 23 atoms C 1mol NaCl = 6.02 x 10 23 formula units NaCl 1mol SO2 = 6.02 x 10 23 molecules SO2

How big is a mole? https://www.youtube.com/watch?v=TEl4jeETVmg

THE MOLE 1 mole = 6.02 x 1023 particles We can convert using factor label!! 1. What do you know? 2. Start with what you are given 3. Set up your identity. x ------ 4. Whatever unit is on top goes on the bottom. 5. Plug in conversion factors 6. Cancel Units! Multiply by top… Divide by bottom. Answer should have same # of sig figs as given

Example How many atoms are in 2.5 moles of tin? 6.02 x 1023 atoms What do we know about moles and atoms? 1 mole = 6.02 x 1023 atoms! 6.02 x 1023 atoms 2.5 moles x = 1.5 x 1024atoms 1 mole

Example How many moles are equivalent to 550 molecules of SO3? What do we know about moles and molecules? 1 mole = 6.02 x 1023 molecules! 1 mole 550 molecules x = 9.1 x 10-22 mole 6.02 x 1023 molecules

Homework Mole-Particle Conversions

4/6/16 Today I will measure the mass of a mole Warm Up – What do you know about the mass of an atom?

How much is a mole? The mass of an atom is based on how many protons and neutrons it has. Since all atoms have different masses, one mole (6.02x1023atoms) would also have different masses!

How much is a mole?

Mass Atomic Mass Based on protons + neutrons Average of isotopes on the periodic table Atomic Mass Units What is the atomic mass of zinc? 65.38 amu Since the actual mass of an atom is so small, these are relative mass units. Relative to the mass of each atom.

Formula Mass Formula Mass Sum of the atomic masses for all elements in a compound. Also in amu

Find the atomic mass of each atom rounded to the tenth Formula Mass Find the atomic mass of each atom rounded to the tenth Multiply by the number of each type of atom Add up the atomic masses (unit amu)

Formula Mass Determine the formula mass of acetic acid, HC2H3O2. H – 1.0 x 4 = 4.0 12.0 x 2 = 24.0 16.0 x 2 = 32.0 60.0 amu

Molar mass - Mass in grams of 1 mole of any substance. Equivalent to the formula/atomic mass. Examples: Molar mass of Zn = 65.4 g Molar mass of HC2H3O2 = 60.0 g

Mass What’s the difference? Atomic/Formula mass is the mass on ONE particle (amu) Molar mass is the mass of 6.02 x 1023 particles (g)

WHAT DO WE KNOW? 1 mole = 6.02 x 1023 particles 1 mole = molar mass (g)

Converting 1 mole = molar mass (g) 1 mole = 18.0g 18.0 g 2.5 moles What is the mass of 2.5 moles of water (H2O)? 1 mole = molar mass (g) 1 mole = 18.0g H – 1.0 x 2 = 2.0 O – 16.0 x 1 = 16.0 18.0g 18.0 g 2.5 moles x = 45 g 1 mole

Converting How many moles in 128 g C6H12O6 (glucose)? 1 mole = molar mass (g) 1 mole = 180.0g C – 12.0 x 6 = 72.0 H – 1.0 x 12 = 12.0 O – 16.0 x 6 = 96.0 180.0g 1 mole 128 g x = 0.711 mole 180.0 g

Homework Mole-Mass Conversions Remember: 1 mole = 6.02 x 1023 particles 1 mole = molar mass (g)

4/7/16 Today I will measure the number of moles in a gas. Warm Up – What are our 2 mole conversion factors?

MOLAR VOLUME 1 mole of any gas (at STP) will always occupy 22.4 L of space. STP – Standard Temperature and Pressure (1 atm and 0°C)

THE MOLE 1 mole = 6.02 x 1023 atoms/molecules/F.U.s 1 mole = molar mass (g) 1 mole = 22.4 L (of gas at STP)

How many liters are equivalent to 0.25 moles of O2 at STP? Mole Conversions How many liters are equivalent to 0.25 moles of O2 at STP? 1 mole = 22.4 L 22.4 L 0.25 mole x = 5.6 L 1 mole

Homework 1-step mole conversions review

4/8/16 Objective – to perform 2 step molar conversions Warm Up – What is the molar mass of Mg3(PO4)2?

2 step conversions Molar Conversions How many grams are in 31.5 L of nitrogen gas (N2) at STP? We don’t have a conversion that relates grams and liters???

Particles (atoms, molecules, fu) Volume (L) Mass (g) Particles (atoms, molecules, fu) 1 mol = 22.4 L 1 mol = molar mass (g) 1 mol = 6.02x1023 p

MOLE CONVERSIONS How many grams are in 31.5 L of nitrogen gas (N2) at STP? L  mol 1 mole = 22.4 L mol  g 1 mole = molar mass 1 mole = 28.0g 1 mole 28.0 g 31.5 L x x = 39.4 g 22.4 L 1 mole

Practice Problem #1 How many molecules of hydrogen gas are in 210g H2? 1 mol = molar mass 1 mol = 2.0 g 1 mol = 6.02x1023 molecules 1 mole 6.02x1023 molecules 210 g x x = 6.3 x 1025 molecules 2.0 g 1 mole

Practice Problem #2 What is the volume (in L) of 2.0 x 1024 atoms of Argon? 1 mol = 6.02x1023 atoms 1 mol = 22.4 L 1 mole 22.4 L 2.0x1024 atoms x x = 74 L 1 mole 6.02x1023 atoms

Homework Two Step Mole Conversions

4/11/16 Objective – to practice mole conversions Warm Up What is the molar mass of Al2(SO4)3

Practice How many moles are in 5.7 x 1022 molecules of water?

Practice How many molecules are there in 75 grams of MgCl2?

Practice What volume will 3 moles of carbon dioxide occupy?

Practice How many grams are in a 2.3 L balloon full of Xenon?

Homework All Mole Conversions Review 42 g 430g (431.36 g) 1 x 1023 molecules (1.34 x 1023) 0.274 mol 100,000 g (125,000) 5 x 1023 molecules (4.816x1023) 240 L (241.86) 3.7 x 1024 atoms 5.27 x 1023 molecules 56.8 L 9440 g (9438.1) 1.34 x 1024 molecules 5.2 mol

4/12/16 Objective – to calculate percent composition Warm Up How many molecules are in 12.2 L of CO2 gas at STP?

Quiz

Type 1: Percent Composition The percent by mass of each element in a compound.

Type 1: Percent Composition Determine the % composition of each element in the following compound: Na2SO4

Type 1: Percent Composition Determine the % composition of each element in the following compound: Al2(CO3)3

Type 1: Percent Composition Hydrates – compounds that contain water. Example : MgSO4  5H2O Determine the formula mass of this compound. (Here, we want to look at the water separately)

Type 2: Percent Composition of Data Determine the percent composition of a compound that contains 2.20 g sulfur and 3.30g of oxygen.

4/13/16 Today I will continue to solve percent composition problems Warm Up – What is the percent composition of aluminum chlorate?

Type 3: Using Percent composition. Determine the mass of an element in a given quantity of a compound. Example: Determine the mass of Ag in 120g of AgCl. Ag – 107.9x1 = 107.9g Cl – 35.5x1 = 35.5 g 143.4 g so…. 75.2 % of 120g = mass Ag 0.752 x 120 g = mass Ag 90.2 g = mass Ag 107.9g/143.4g x 100 = 75.2% Ag

Type 3: Using Percent Composition 1. Determine the mass of Ca, in 400g of CaCO3. Answer: 160g.Ca 2. Determine the mass of K, in 50g of KClO34H2O. Answer: 10.0 g K

Homework Percent Composition & Conversions Review WS

4/14/16 Objective – to determine empirical formulas Warm Up – What is the percent composition of magnesium nitrate?

Determining Chemical formulas Empirical Formula (Simplest Formula)– Smallest whole number ratio of atoms in a chemical formula. For ionic compounds, we always have the empirical formula (that’s why we reduce/cancel). For covalent compounds, the empirical formula can be different from the actual formula!

Calculating an Empirical Formula: 1. If given percent: Take the given % and change to grams. (You have assumed 100g) If given grams: Leave them in grams! 2. Convert each value to moles. (using factor label) 3. Divide all answers by the smallest value. (ratio) 4a. If all answers are very close to whole numbers, round to the nearest whole number. b. If not, then multiply each by the same whole number to give a whole number value for all elements. 5. Write the formula with the ratio values as subscripts

Answer : Na2SO4 Practice Problem Find the simplest formula for a compound that contains 32.38% Na, 22.65% S, 44.99% O. Answer : Na2SO4

Answer: K2Cr2O7 Sample Problem Determine the simplest formula for a compound that contains 26.56% K, 35.41% Cr, 38.08% O. Answer: K2Cr2O7

Review Problem #44. Find the empirical formula for a compound which contains 6.5g K, 5.9g Cl and 8.0g O.

Homework Empirical Formulas & Mole Review WS

4/15/16 Hydrate Lab

4/18/16 Today I will write molecular formulas Warm Up - Determine the empirical formula for a compound that is 75% Carbon and 25% Hydrogen.

Calculating the Molecular Formulas Molecular Formula – is a multiple of an empirical formula; tells the actual number of atoms of each element in a molecular compound For example, if the empirical formula is CO2, possible molecular formulas are C2O4 and C6O12 Molecular Formula = (Empirical Formula)x “Multiplier”

Calculating the Molecular Formulas Molecular Formula = (Empirical Formula)x Molecular mass – mass of the molecular formula. This must be given in the problem Empirical formula mass – mass of the empirical formula. This is found through calculations

Molecular Formula 1st step – determine the empirical formula 2nd step – determine the mass of the empirical formula 3rd step – determine the multiplier (x) *Round to whole # 4th step – multiply empirical formula by x

(CH)6 = C6H6 Sample Problem Determine the molecular formula of a compound having a simplest formula of CH and a formula mass of 78.110g Step 1: Empirical formula is done for you: CH! Step 2 – Mass of empirical Formula: 13.0g Step 3 Step 4 (CH)6 = C6H6

Sample Problem #2 A compound with a formula mass of 34g is found to consist of .44g H and 6.92g O. What is its molecular formula?

Ribose is an important sugar that is found in DNA and RNA Ribose is an important sugar that is found in DNA and RNA. Ribose has a molar mass of 150 g/mol and a chemical composition of 40.0 % Carbon, 6.67 % hydrogen and 53.3 % oxygen. What is the molecular formula for ribose?

Homework Molecular Formulas WS

4/19/16 Objective – to review problems Warm Up – How many molecules are in 32.1 L of CO gas?

Types of Problems Mole Conversions Molar Mass One step Two step % Composition Type 1 - % comp of formula Type 2 - % comp of data Type 3 – Using % comp Empirical Formulas Write in grams Convert to moles Divide by smallest Round to whole # (or multiply) Make #’s subscripts Molecular Formulas Empirical Formula Mass of Empirical Formula Multiplier Multiply

4/20/16 Today I will review chapter 10 The explosive, TNT, is composed of 37.0% C, 2.20% H, 18.5% N and 42.3% O. a) Determine the empirical formula for TNT. b) The molar mass for TNT is 227g/mol. What is the molecular formula for TNT?