March 20

DO NOW Q:List everything that you know about the mole and its uses.

Announcements:

Important Dates: (that means…write it down in your calendar)

Unit 6 Notes-

Chemical MeasurementsWhat are all the different ways in which we make measurements in chemistry?-Counting-Massing-Measuring out volume, etc.

Which technique we employ is determined, in large part, by our purpose.

It is also necessary, when determining which technique to use, to consider what type of measurement is easiest to make or even feasible. Consider the chemical reaction below:

Cl2(g) + 2KI(aq) —> 2KCl(aq) + I2 (s)

The number of molecules and formula units that interact is know, but it’s impossible to actually study this reaction at the atomic level in a chemistry laboratory; we cannot count out just one or two atoms or molecules of anything! We have to use another way to measure out the necessary quantities of chlorine and potassium iodide.

The MoleA mole is a quantity of something just like a dozen (12), gross (144), or ream (500).

We use these more familiar quantities to count out large quantities because it’s more convenient. We can convert from the individual item to the quantity units by using simple conversion factors.

Try the problems below using factor labeling:•5 dozen eggs = ______________ eggs•1152 pencils = _______________ gross of pencils•5000 pieces of paper = ______________reams of paper

5 dozen eggs = ______________ eggs

1152 pencils = _______________ gross of pencils

5000 pieces of paper = ______________reams of paper

mole = the number of atoms of an element that would be found in, say, 12.01 grams of carbon-12 or 14.01 grams of nitrogen-14 (the molar mass)

mole = ____________ atoms (this number is called “________________ number”)

mole =_________ L of any gas at STP (standard temperature and pressure: 273 K and 1.0 atm)

6.02 x 1023 Avogadro’s

22.4

one atom of Ar = _______ amu

one mole of Ar atoms =______ g = molar mass of Ar

one atom of Na = __________ amu

one mole of Na atoms ______ g = molar mass of Na

one atom of Pb =_______ amu

one mole of Pb atoms= ________ g molar mass of Pb

one atom of B = ________ amu

one mole of B atoms = ________ g = molar mass of B

This means that we can use the atomic masses on the periodic table to convert instantly to grams. The mass of one mole of atoms is called the molar mass. Use the periodic table to determine the following:

39.9 207.2

39.9 207.2

23.0 10.8

23.0

10.8

Simple Conversions Using Mole Equivalencies

grams Atomic mass in grams

6.02 x 1023 particlesparticles

Liters of gas 22.4 L

34.5g

Practice 1: Do the following conversions using the mole equivalencies above. Use factor labeling and show your work.

a) 2.0 mol Ni = _______ g Nib) _________mol C = 24.02 g Cc) ___________mol Ca = 4.75 x 1026 atoms Cad) 0.115 mol Xe = __________L of Xe

Atomic masses of elements formula mass of a compound molar mass of a compound

We can work easily with the mass of a compound in the same way

we do with elements. Determine the mass of a unit of sodium

chloride or calcium fluoride by adding up _______________of the

component elements in their proper ____________. The sum is

called the ________________

one atom of Na = ___________ amu one atom of Ca = ____________ amu

one atom of Cl = ____________ amu two atoms of F = ____________ amu

formula mass of NaCl = _______amu formula mass of CaF2 = ________ amu

atomic mass

formula mass

ratio

23.0

35.5

58.5

2 (19.0)40.1

78.1

The molar mass of a substance is determined the same way, but you are finding the mass of ________ instead of the mass of just one ________ (for a covalent compound) or one __________ (for an ionic compound). molar mass of NaCl = ________ g

molar mass of CaF2 = ________ g molar mass of H2O _________ g

molar mass of K2SO4 = _______ g molar mass of SO3 _________ g

molar mass of Cl2 = __________ g

one molemolecule

formula unit

58.578.1

18.016

174.3

80.1

71

http://ed.ted.com/lessons/daniel-dulek-how-big-is-a-mole-not-the-animal-the-other-one