Chapter 10

 Identify the number that each word refers to:  Couple - _______________  Dozen - _______________ Use dimensional analysis to solve the following problems. a. A cake recipe requires 8 eggs. How many dozens of eggs are required to make 5 cakes?

 The mole represents a large number of extremely small particles.

 How is the mole used indirectly to count the number of particles of matter?  What is a common everyday counting unit that the mole can be related to?  How can moles be converted to number of representative particles and vice versa? Vocabulary  Avogadro’s Number  Mole  Molecule

 SI base unit used to measure the amount of substance. 1 mole = x mole = 602,213,670,000,000,000,000,000  Abbreviated as mol

1 mole

THE MOLE IN PERSPECTIVE 1. One mole of paper would make a stack that would reach to the moon more than 80 billion times 2. One mole of grains of sand would be more than all of the sand on Miami Beach 3. One mole of blood cells would be more than the total number of blood cells found in every human on earth

4. A one liter bottle of water contains 55.5 moles of water 5. One mole of seconds is about 19 quadrillion years, 4,240,666 times the age of the earth, or 954,150 times the age of the universe itself 6. One mole of cents could repay the United States National Debt 86 million times THE MOLE IN PERSPECTIVE

MOLES & PARTICLES  How many molecules are in 3.0 moles of H 2 O?  How many moles of Aluminum, are in 4.02 x atoms of Al?

Section 2

 Why can the mass of an atom be related to the mass of a mole of atoms?  How can the number of moles be converted to the mass of an element and vice versa?  How can the number of moles be converted to the number of atoms of an element and vice versa? Vocabulary  Conversion Factor  Molar Mass

MOLAR MASS:  The mass of one mole of pure substance  Units are always expressed as grams per mole (g/mol)  Ex. Lithium = 6.94 g/mol

CALCULATE THE MOLAR MASS OF:  Cu  NaCl  Ca 2 SO 4  Al(NO 3 ) 3

MOLAR CONVERSIONS:

 How many moles of oxygen in 3.98 g of oxygen?  How many moles of carbon in 5.01 grams of carbon?

 Calculate the molar mass of Au (gold).  How many grams are in two moles of Au?

MOLES & MASS  What is the mass of 3.0 mols of NaCl?  How many mols are in 30.0 g of H 2 O?

MOLES & PARTICLES & MASS  Calculate the mass of 3.7 x molecules of MgCl 2.  How many atoms are in 100.0g of Silver?

Section 3

 What are the mole relationships shown by a chemical formula?  How is the molar mass of a compound calculated?  How can the number of moles be converted to the mass of a compound and vice versa?  What conversion factors are applied to determine the number of atoms in a known mass of compound? Vocabulary  Representative particle

 Chemical formulas give the relative numbers of atoms or moles of each element in a compound  Always a whole number ratio.  Example:  n determine the formula for the compound by knowing the relative number of moles of each element in a compound.

Section 4

 What is mean by the percent composition of a compound?  How can the empirical and molecular formulas for a compound be determined from mass percent and actual mass data? Vocabulary  Percent by mass  Percent composition  Empirical formula  Molecular formula

 Percent by mass of each element in a compound.  % composition of any pure substance is always constant, whatever the source or sample size.  Useful in identifying the characteristic of any substance.  Used by investigators from many fields, Analytical chemistry, forensics etc. to determine the identity of unknown materials.

 Remember that percentage of anything is part over whole:  For elements in a compound, do mass of element over mass of compound.

 Calculate the percentage composition of each element in NaNO 3.  27.05%Na, 16.48% N, 56.47% O  Calculate the percentage composition of Oxygen in Ag 2 SO 4.  69.19% Ag, 10.28% S, 20.52% O

 Empirical formulas – consists of the symbols for the elements combined in a compound, with subscripts showing the smallest whole-number ratio of the different atoms in the compound.  Molecular Formulas – a multiple of the empirical formula.

 Determine the mass of each element  Convert into moles  Divide by the smallest mole or the elements present  Determine the ratio  Write the formula (Usually elements are listed from left to right on the Periodic Table of Elements)

 Determine the empirical formula of a compound that is composed of 36.5% sodium, 25.4 % sulfur, and 38.1 % oxygen.  STEP 1: Find the number of moles of each element present. Since the amount of each element is given in percentage, you must convert the percentage to a mass. If 100 grams of the sample are assumed, the percentages given are the same as grams.

 STEP 2: Determine the whole number mole ratio. Divide each mole number by the smallest mole number.  STEP 3: Use the mole ratio for the subscripts of each element in the formula. Na 2 SO 3

 A compound is analyzed and found to contain 36.70% K, 33.27% Cl, and 30.03% O. What is the empirical formula of the compound?  A g sample of tetramethyllead, a gasoline additive, is found to contain g of lead, of carbon, and hydrogen. Find its empirical formula.

Section 5

 What is a hydrate and how does its name relate to its composition?  How is the formula of a hydrate determined from laboratory data? Vocabulary  Crystal lattice  hydrate

 Must drive off the water by heating the compound  Substance remaining after heating is anhydrous (without water)  Example: Hydrated cobalt (II) chloride is a pink solid that turns a deep blue when the water of hydration is driven off and anhydrous cobalt (II) Chloride is produced.

 To determine the formula for a hydrate, you must determine the number of moles of water associated with one mole of the hydrate.

 2.50 g CuSO 4 · x H 2 0  1.59 g CuSO 4  0.91 g H 2 0 (Hydrate – Anhydrous) CuSO 4 · 5 H 2 0

 Drying Agents:  Storage of solar energy