THE MOLE... a unit of counting Quantities in Chemical Reactions

Big Ideas Relationships in chemical reactions can be described quantitatively The efficiency of chemical reactions can be determined and optimized by applying an understanding of quantitative relationships in such reactions.

How Scientists Keep Track of Atoms One way to measure how much of a substance is available is to count the # of particles in that sample However, atoms & molecules are extremely small To solve this problem, scientists developed the concept of the mole SYMBOL IS n. *The mole is a unit songThe mole is a unit

The Mole A dozen donuts = 12 A mole of donuts = 6.023x10 23 a dozen shoes = 12 A mole of shoes = 6.023x mole = 6.02 x entities of a substance 1 mole of anything = 6.023x10 23 = 602,000,000,000,000,000,000,000!!!

WHAT IS THE MOLE? Avogadro’s Constant = N A = x particles 1 mol Units of moles are mol Different types of particles include: atoms OR molecules OR ions OR electrons OR formula units, etc. FYI…. A formula unit is a term used to represent the lowest whole number ratio of ions in an ionic compound. On your calculator: EE or EXP or x10^

WHERE DID THIS NUMBER COME FROM? A mole is the amount of substance that contains as many particles as exactly g of Carbon-12

The Mole- Examples 1 mole of carbon contains 6.02 x atoms of carbon 1 mole of H 2 O contains 6.02 x molecules of H 2 O 1 mole of NaCl contains 6.02 x formula units of NaCl

How Big is Avogadro’s Number? ◦ 6.02 x ÷ 1,000,000 = 6.02 x d o 6.02 x d ÷ 365 d/a = 1.65 x a If you had one mole of dollars, how long would it take to spend it at a rate of $1,000,000 per day? Put this into perspective… o The sun is about 4.6 x 10 9 years old and will burn out in about 5 x 10 9 years. o You will need to spend faster!!

The mole is a BIG number. The green pea analogy puts it into perspective as well: Did you know that 12 pencils will contain a mole of carbon atoms?

Variables to Know n = number of moles N = number of particles N A = Avogadro’s number (6.02 × ) Two possible types of questions: o Moles to Particles  N = n x N A o Particles to Moles  n = N / N A N NANA n

Using Avogadro’s Constant How many atoms in 2 moles of carbon? N = n x N A = 2 moles x (6.02 x ) = 1.2 x particles of C How many moles is 5.0 x particles of iron? n= N / N A = 5.0 x /6.02 x = 8.3 moles of Fe How many atoms in 2 moles of water? N= n x N A = 2 moles x 6.02 x = 1.2 x molecules of H 2 O = 3 atoms per molecule = 3 x (1.2 x ) = 3.6 x atoms in 2 moles of H 2 O

LEARNING CHECK (round to 3 sig. figs.)  How many molecules of CO 2 are in 4.56 moles of CO 2 ?  How many moles of water is 5.87 x molecules?  How many moles is 7.78 x formula units of MgCl 2  How many atoms of carbon are in 1.23 mol of C 6 H 12 O 6 ? 2.75 x molecules mol (or 9.75 x ) 4.44 x atoms C 12.9 moles

Mass to Mole Calculations Atomic Mass ◦Mass of one atom ◦Unit μ = atomic mass unit = a.m.u  Eg. Each hydrogen atom has a mass of 1.001μ ◦1 μ equals approximately 1.67 x g, which is extremely small and not practical to measure. Enter Molar Mass….

Molar Mass (MM) The mass of 1 mole of a substance Mass of x particles Units are g/mol ◦Eg. The molar mass of Hydrogen is 1.01 g/mol

Molar Mass Molar mass and atomic mass have the same numbers except there is a unit difference. The g/mol unit is more useful that μ because… It can be measured in the lab using a scale Atomic MassMolar Mass Li6.94 μ/atom6.94 g/mol Ag μ/atom g/mol

Example Eg. Find the molar mass of water: H 2 O H: 2 x 1.001g/mol O: 1 x g/mol g/mol Eg. Find the molar mass of calcium phosphate: Ca 3 (PO 4 ) 2 Ca: 3 x g/mol P:2 x g/mol O: 8 x g/mol 310.2g/mol

 The same as:  Gram Molecular Mass (for molecules)  Gram Formula Mass (ionic compounds)  Gram Atomic Mass (for elements)  molar mass is just a much broader term than these other specific masses

Mole Calculations MM m n MM = m/n n = m/MM m = MMn N = nN A n = N/N A

HOMEWORK Complete Moles Worksheet. Try all questions to the best of your ability. Good luck!