Objective: To reintroduce the mole and introduce two mole conversions Do Now: Solve each proportion = x2. 10 = x

When converting units, use PROPORTIONS! Units _______________ = ________

Example 1 An experiment requires each student to have 8.5cm of magnesium ribbon. If the ribbon is 570cm in length, how many students can conduct the experiment? Units _cm____8.5cm_ = _570cm_ students1 student x student

Example 2 If 0.2 bushel is 1 dozen apples, and 1 dozen apples is 2.0kg, what is the mass of 0.50 bushel of apples? Units _bushels____bushels = ___bushels kg kgkg

The mole Si unit for specified number of particles 1 mole = x (Avogadro’s number) Representative particle- refers to species present in a substance (atoms, molecules, or formula unit)

Representative Particles and Moles SubstanceRPRP in 1 mole Copperatom 6.02 x Watermolecule 6.02 x calcium formula unit6.02 x fluoride

Converting Between Number of particles and Mole 1mol = x (Avogadro’s number) – How to enter this into the calculator:

Using a Calculator: Try evaluating these expressions using the calculator ! = _____

Sample Problem # of atoms of Magnesium = 1.25 x Convert to moles Units __mole 1 mole = x mole__ # of atoms x x 10 23

Try these out How many moles are equal to 2.80 x molecules of silicon? Units ______________ = ________ How many moles are equal to 2.17 x10 23 molecules of bromine? Units _______________ = ________

Molar Mass You learned in chapter 4 that atomic mass is the average masses of single isotope atoms These units are expressed in atomic mass units (amu) In laboratories, it is convenient to work in grams than atomic mass unit

Molar Mass (cont) The atomic mass of an element expressed in grams is the mass of a mole of the element Atomic mass expressed in grams has a unit of grams/mole Example: Molar mass of carbon is g/mol

Other molar mass examples Water (H 2 O) = (1x2)H + (16x 1)O = 18 g/mol Ammonia(NH 3 ) = (___ x 1)N + (___x3)H= 17 g/mol Sodium chloride(NaCl) = (__ x1 )N + (___ x 1)Cl = _____ g/mol

Try These Out Find the molar mass of the following representative particle: Bromine (Br) (hint. It is a diatomic molecule) Aluminum (Al) Calcium Fluoride (CaF)

Objective: To calculate the molar mass of elements. Do Now: Taking the mass of the element from the Periodic Table, find the molar mass of the following: Magnesium Sodium chloride (NaCl)

Steps to find the Molar Mass Look up the atomic mass on the Periodic Table of an element. Multiply the atomic mass by its subscript, if any. Repeat steps 1 and 2 for other elements in compound. Add the molar masses together.

Converting moles to grams molar mass = grams/mole 1.Determine molar mass. 2.You will use the representative particle’s molar mass to convert to moles. Molar mass = ____g___ 1 mol mol

Sample: Find the mass of 2.50 mol of Fe(OH) 2 First, determine the molar mass of iron (II) hydroxide ______ = ___x____ 1 mol 2.50 mol

Try this out Convert 75.0g of N 2 O 3 to moles How much does 3.45 moles of Al 2 O 3 weigh?

Percent Compound: percent by mass of each element in the compound. % of element = mass of element x 100 mass of compound Percent Composition

Find the percent composition of Magnesium Oxide. 1. Find the molar mass. Magnesium (24.3 g/mol) + Oxygen (15.99 g/mol) Molar mass (40.29 g/mol) 2. Use the formula for percent composition. % of Mg= (24.3 / 40.29) x 100 = 60.31% % of O = (15.99 / 40.29) x 100 = 39.69%

Calculate the percent composition of each element in ethane (C 2 H 6 ) 1. Molar Mass = 2. % of C = % of H = Try this out

Which compound has the largest % composition of nitrogen (NH 3 or NH 4 NO 3 ) Try this out

Standard temperature and pressure: (STP) – Temperature = O degrees Celsius or 273 kelvin – Pressure = kilopascal (kPa) or 1 atmosphere (atm) Moles to Volume Conversion

At STP, 1 mole (6.022 x representative particle) of any gas is 22.4L 22.4L is known as molar volume of a gas 22.4L = 1 mole (this is how you convert moles to volume) Mole to Volume

Determine the volume, in liters, of 0.60mol SO 2 at STP. (1 mole SO2 = 22.4L SO2) 22.4 L = __x___ 1 mol 0.60 mol Sample Problem

What is the volume of 3.70mole N 2 at STP? At STP, how many moles are in 0.880L He? Try these out