The Mole Q: how long would it take to spend a mole of $1 coins if they were being spent at a rate of 1 billion per second?

Essential questions 1. How is a mole used to indirectly count the number of particles of matter? 2. What is a common everyday counting unit which the mole can be related? 3. How can moles be converted to number of particles and vice versa? MAIN IDEA: Chemists use the mole to count atoms, molecules, ions and formula units.

The Mole The mole is the SI unit for amount of a substance. Definition 1 : A mole is the amount of a substance that contains as many particles as there are in exactly 12 grams of carbon-12.

A Mole Definition 2 : The amount of a substance that contains Avogadro’s number of particles.

Counting Particles Dozen = 12 Ream = 500 sheets Pair = 2 Units for counting, each are appropriate for certain types of objects. Mole = x representative particles

Avogadro’s Number  The mole is also known as Avogadro’s number  Named after Amedeo Avogadro – Italian physicist and lawyer  In 1811 determined the volume of 1 mol of gas  For most purposes we will round it to 6.02 x Remember how to do scientific notation!?

How big is a mole? Avogadro's number of inches is 1,616,434 light years, or across our galaxy and back 8 times. Avogadro's number of seconds is about 19 quadrillion years, 4,240,666 Avogadro's number of cents could repay the United States National Debt 86 million times. United States National Debt Avogadro's number of kilograms is just over 20 times the mass of the earth.

6.02x10 23 PEEPS

The pile of PEEPS would cover the US…

6.02x10 23 PEEPS and be as tall as Mt. Everest.

6.02x10 23 dollar bills

You would spend $1,000,000,000/sec

6.02x10 23 dollar bills spend $1,000,000,000/sec 19 million years to spend

6.02x10 23 pieces of paper

would form a stack tall enough

6.02x10 23 pieces of paper to extend from the sun to Pluto

6.02x10 23 pieces of paper to extend from the sun to Pluto

Moles of substances *Now that you understand just how large a mol is, let’s understand how small atoms are! 1 mol of copper atoms has a mass of g 1 mole of carbon atoms has a mass of g 1 mole of water molecules has a mass g and is 1 mole of sugar molecules has a mass of 1 mole of salt has a mass of g If they all have the same number of particles, why are does 1 mol of each have a different mass?

Calculating # of particles Just like the word dozen, means you have 12 of something. A mole means you have x of something. If you have 2 dozen eggs, you have 2 x 12 eggs If you have 2 moles of eggs you have 2 x x eggs

Calculating the # of particles If you have 0.5 dozen eggs, you have 0.5 dozen x 12 eggs = 6 eggs 1 dozen If you have 0.5 mol of carbon, how many carbon atoms are there? 0.5 mol of carbon x x C atoms = 3.0 x atoms 1 mol of carbon

Used as Conversion factor 1 mole/ x particles x particles / 1 mole Practice converting: How many moles of lead, Pb are in 1.50 x atoms? Get in HABIT of showing work!(write out conversions) Answer 2.49 x mol Pb

More practice Solve the following: How many atoms of zinc are in 7.48 mols of zn? Calculate the number of molecules of H 2 O in 11.5 moles of H 2 O How many moles contain 5.75 x atoms of Al? For examples and help see pages in textbook.

Day 2

Mass and the Mole Essential Questions: 1. Why can the mass of an atom be related to the mass of a mole of atoms? 2. How can the number of moles be converted to the mass of an element?

Day 2 Essential Questions: 1. Why can the mass of an atom be related to the mass of a mole of atoms? 2. How can the number of moles be converted to the mass of an element? MAIN IDEA: A mole always contains the same number of particles, however, moles of different substances have different masses.

Relative Atomic Masses To set up a relative scale of atomic mass, one atom was chosen and assigned a mass value. (Carbon-12) The mass of all other atoms are expressed in relation to this one. One Atomic Mass Unit – or AMU is exactly 1/12 of the mass of the Carbon-12 atom

Atomic Mass Units The carbon-12 atom has been assigned 12 AMU’s Therefore in relation - Hydrogen is approximately 1 AMU Activity – Find how many amu’s are the following. 1. Iron 2. Chlorine 3. Magnesium 4. Why aren’t they whole numbers? Well……

Review What 3 parts is an atom made of? 1. Proton – positive - in nucleus 2. Neutron – neutral – in nucleus 3. Electron - negative - outside of nucleus and much smaller than protons and neutrons.

Average Atomic Masses of Elements In nature, elements occur as a mixture of isotopes. Isotopes are the same element with a different number of neutrons so the mass is different. The percentage of each isotope is always the same, no matter where it is found. Average Atomic Mass is the weighted average of the atomic masses of the naturally occurring isotopes of an element. This is what is on the periodic table.

Example – Carbon There are 3 naturally occurring isotopes of carbon: 12, 13, and C and 13 C are stable, occurring in a natural proportion of approximately 99:1.isotopes

Molar Mass The mass in grams of 1 mole of a pure substance is called the molar mass. The molar mass of an element is = to the atomic mass of the element in atomic mass units (found on the periodic table) – but has the units g/mol

Molar Mass Molar Mass is written in units of g/mol Molar mass can be used as a conversion factor to convert from moles to mass (grams) and back.

Using Molar Mass Suppose while working in the lab you need 3.00 mol of copper for a reaction. How would you measure that amount? The molar mass of Cu is g/mol from the periodic table. So set up a conversion! The answer is 191g.

How are the terms “molar mass” and “atomic mass” different from one another? Molar mass is used to describe the mass of one mole of a compound or element. Atomic mass is used to describe the mass of one atom of an element in AMU’s But they are the same numerically. NOTE : one atom cannot be weighed in grams! It is too small!

MORE PRACTICE! Show your work What is the mass in grams of 3.57 mol of Al? How many moles is 525 g of Ca? Determine the mass in grams from 5.50 x atoms of He.

Avogadro’s Hypothesis Equal volumes of gases at the same temperature and pressure have equal numbers of molecules. This is what led to relative masses