Ch. 10- The Mole

Why- Within the next 2 months we will be working with chemical quantities. Determining what a reaction will produce or how much we need to go into a reaction with. These math skills can be applied across all science, ALL

professions and many day to day life activities.

Measuring MatterCount, Mass, Volume……

Units indicating a specific number of itemsExamples????

Remember your dimensional analysis….well lets get those gears agrindingWhat is the mass of 90 apples if 1 dozen of the

apples has a mass of 2.0kg

Jan 25- “Mole Day”Hey you….don’t be miserable today…you don’t

want to be labeled as being dismole

Why is it hard to count atoms, ions, or molecules 1x1?

We as chemists use the mole (mol) in the same way we use dozen1 mole = 6.02 x 1023 representative particles

Avogadro’s number- named after him to honor his work on molecular theories

How big is a mole?

If you count to 6.02 x 1023, one number per second, how long will it take?

6.02 x 1023 x 1min/60sec x 1hr/60min x 1 day/24 hr x 1 yr/365 days =

1.9 x 1016 years = 19 quadrillion years!

The earth is 4.6 billion years old, so that’s 4 million times the earth’s age!

Representative particlesRefers the the species present in a substance

Na = atomsCO2 = molecules

NaCl = formula unit

So……

1 mole of Na = 6.02 x 1023 atoms1 mole of CO2 = 6.02 x 1023 molecules

1 mole of NaCl = 6.02 x 1023 formula units

Mole Calculations Representative particle mole

The magnesium we have used in labs is used to make aircraft, auto wheels, tools, and garden furniture. How many moles of magnesium is 1.25 x 1023 atoms of Mg

1.25 x 1023 atoms Mg x ______1 mole _______ =

6.02 x 1023 atoms Mg

2.08 x 10-1 mol Mg

Cont.

Moles Representative Particles

Propane gas (C3H8) is used in cooking and heating. How many molecules are in 2.12 moles of propane.

2.12 mol C3H6 x 6.02 x 1023 molecules C3H6 =

1 mol C3H6

Practice1. What is Avogadro’s #?

2. What is the representative particle for MgS?

3. How many formula units are in 2.34 moles of NaNO3?

4. How many moles are in 3.48 x 1024 atoms of Li?

Remember our friend amu?Decimal from periodic table

Relative values based on the mass of Carbon-12 isotopeSince ratio is relative, changing the unit will not

change the ratioGrams is convenient to use in lab so….lets us it

Molar Mass (IMPORTANT)The atomic mass of an element expressed in grams

is the mass of 1 mole of an element = molar massMolar mass of Mg = 24.3g

round off to 1 decimal place

Find the Molar mass of the following:

K =

Cu =

Na =

“How does a mole turn on the tv…….

….with a remolte control!!!!!”

Molar mass of CompoundsSimply…add the masses of all the elements in

the compound togetherEx. SO3

EX. C9H11NO2

On your own…try

1.) K3PO4

2.) Al2(SO4)3

Mole Land…. Where the fun is multiplied by 6.02 x 1023 times

Mole Mass problemsUse molar mass to convert between moles and

mass

When aluminum reacts with oxygen in the air a tough coating of aluminum oxide(Al2O3) is formed. What is the mass of 9.45 mol of aluminum oxide?

molar mass

9.45 mol Al2O3 x 102.0g Al2O3 = 964 g Al2O3

1 mole Al2O3

Mass Mole Problems

How many moles of Iron (III) Oxide are contained in 92.2 g of pure Fe2O3?

92.2 g Fe2O3 x 1 mole Fe2O3 = 0.578 mole Fe2O3

159.6 g Fe2O3

molar mass

Molar VolumeAvogadro’s hypothesis- equal volumes of

gases at the same temp. and pressure contain equal number of particles

Volume measured at STP (Standard Temp. and Pressure)0°C and 101.3kPa (1 atm)

Molar volume = At STP, 1 mole or 6.02 x 1023 representative particles, of any gas occupies a volume of 22.4 L.

Mole Volume Problems

SO2 is a gas produced by the burning of coal and contributes to the pollution of the environment. Determine the volume, in L, of .60 mol SO2 at STP.

.60 mol SO2 x __22.4 L = 13 L SO2

1 mol SO2

Molar Volume

Volume Mole ProblemsHow many moles would be contained in .200 L of

H2

.200 L H2 x 1 mole H2 = 8.93 x 10-3 mol H2

22.4 L H2

Molar volume

% CompositionRelative amounts of the elements in a

compoundHow important in the real world

% mass of element = _mass of element_ x 100%

mass of compound

% Composition from mass data When a 13.60g sample of a compound containing only Mg

and O is decomposed, 5.40g of O is obtained. What is the % composition of this compound?

% O = _mass of O_ x 100% = 5.40 g x 100% = 39.7 %

mass of MgO 13.60g

% Mg= _mass of Mg__ x 100% = 8.20 g x 100% = 60.3%

mass of MgO 13.60g

% Composition from Chemical Formula

% mass = mass of element in 1 mol compound molar mass of compound

Propane (C3H8) is commonly used in gas grills. What is the percent composition of Propane?

% C = 36.0g x 100% = 81.8%

44.0g

% H = 8.0g x 100% = 18%

44.0g

% PracticeWhat is the percent composition for each

element in the following compounds

C11H12N2O2 -Tryptophan

C6H8O6 – Vitamin C

Magnesium Phosphate