Unit Ten: Introducing the Mole

  What’s a mole? Ted ed video: what is a mole The mole is a unit of measure. Just like meters tells us length and seconds tells us how much time, the mole measures an amount (how much). Units of measure similar to mole include: Dozen = 12 Ream = 500 Mole = 6.02 x 1023

Why do chemists use the mole? The unit mole is based on Avogadro’s number which is equal to 6.023 x 1023. This number is very, very large. Atoms and molecules are very, very small. Since the atoms and molecules are very small, we need a very large unit to describe them. For this reason, the unit mole is mostly used in chemistry.

How small is an atom? How many moles of chalk does it take to write your name? _____ g chalk (CaCO3) I mole ________atoms __________ g CaCO3 1 mole

Unit Conversions: Unit conversions (dimensional analysis) allows us to compare two separate units of measure by using a conversion factor. Example: 2 dozen eggs = ? Eggs 12 eggs = __X___ 1 doz. 2 doz. here’s the math: 2 dozen x 12eggs = 24 eggs dozen [12 eggs/dozen] is the conversion factor that lets us compare eggs & dozen

Unit Conversion & dimensional analysis Set up to cancel units: 2 dozen x 12eggs = 24 eggs dozen This set up allows us to make many comparisons in one calculation: Ex: Convert 12 days to seconds: 12 days x 24 hrs. X 60 min. X 60 sec = 1036800 sec. 1 day 1 hr. 1 min

Unit conversion and dimensional analysis:   Determine the final label by crossing out the units that cancel: 1) mi x hr x min x m x cm = hr min s mi m 1) mi x hr x min x m x cm = cm hr min s mi m s

Unit Conversions: Convert 3.0 centimeters to feet Strategy: cm  inches  feet 3.0 cm x 1 in x 1 ft = 2.54 cm 12 in

Molar Mass Conversions: The unit mole now allows us to relate mass to atoms and molecules. This is important since atoms and molecules are so small , we can use the unit mole to obtain tangible measurements. Molar mass describes how many grams in one mole of an element or compound. It is a conversion factor between grams and moles.

Molar Mass Conversions: Molar Mass describes how many grams in one mole of an element or compound. It is determined just like formula mass. We add the mass of all the contributing elements. This information is found on the periodic table. When converting mass to moles we divide by the molar mass. When converting moles to mass we multiply by the molar mass.

Molar mass conversions: Calculate the molar mass of sodium hydroxide (NaOH) Na = 23.0g O = 16.0g H = 1.0 g 40.0 g/mole Convert 226g of NaOH to moles: Convert 1.4 moles of NaOH to grams: Convert 28.0 grams of NaOH to moles:

the Mole Road: Grams  Moles Find the number of moles in 92.2 g iron Moles  Grams Calculate the mass, in grams, of 0.250 moles of sodium. Moles  Atoms Calculate the number of atoms in 3.2 moles of carbon Grams  Atoms Calculate the number of atoms in 2.5 grams of silver.