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 Measurements What 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: Cl 2 (g) + 2KI(aq) —> 2KCl(aq) + I 2 (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 Mole A 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, grams of carbon-12 or 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 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:

Simple Conversions Using Mole Equivalencies We use mole equivalencies to convert: moles to _______ --> 1 mole of element = _________ moles to the number of _______ --> 1 mole of element = ____________ moles of gas to __________ --> 1 mole of gas = _______ For example: 1.50 mol Na = ________ Na 1.50 mol Na x 23.0 g Na = g Na = 34.5 g Na (sig figs!) 1 mol Na grams Atomic mass in grams 6.02 x particles particles 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 Ni b) _________mol C = g C c) ___________mol Ca = 4.75 x atoms Ca d) 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 CaF 2 = ________ amu atomic mass formula mass ratio (19.0)

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 CaF 2 = ________ g molar mass of H 2 O _________ g molar mass of K 2 SO 4 = _______ g molar mass of SO 3 _________ g molar mass of Cl 2 = __________ g one mole molecule formula unit

Practice 2: More simple conversions using mole equivalencies a. 2.0 mol S0 2 =___________g SO 2 b. _____________ mol F 2 = 1.4 L F 2 c x molecules H 2 O = ______________ mol H 2 O d mol Fe = ______________ atoms Fe f g CO 2 = ______________ molecules CO 2 Multi-step conversions, using mole equivalencies Conversions involving moles, like other conversions, can involve more than one step. When this is the case, it is convenient for you to first plan the conversion. Example problem: 2.3 x molecules H 2 = _____ L of H x molecules H 2 x____ 1 mol H 2 x 22.4 L H 2 = 6.02 x molecules H 2 1 mol H 2 Practice 3: (answer in your composition book): g BeCl 2 = __________ formula units BeCl g H 2 O = __________ molecules H 2 O x molecules I 2 = ____________ moles I L CH 4 = _____________ g CH g NaF = ____________formula units NaF x atoms Ar = ____________ L Ar x molecules Br 2 = __________________ g Br L CO = ______________ molecules CO 9. How many atoms of uranium are in 5.00 g of uranium? 10. What is the volume of 2.6 g of nitrogen gas? 11. What is the mass of 1.0 x molecules of sulfur dioxide? 12. What is the mass of Neon in a sign when the gas tubes have a total volume of 166 mL?

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