Chapter 3

Front 1

Idea behind the mole

Back 1

If we took just the right number of atoms, we could manage to have X grams of an element for which each atom ahas a mass of X u's

Front 2

The convention is to define the masses of all atoms by comparing them to the...

Back 2

12C standard

Front 3

Avogadro's Number

Back 3

The number of atoms of any element that means we have a sample whose mass in grams is equal in magnitude to the mass of each of its atoms in u (6.02214129 x 10^23)

Front 4

1 mole

Back 4

Avogadro's number of things

Front 5

2 ways to interpret the masses given on the periodic table

Back 5

1. Atomic mass of an element (in u)
2. Molar mass of an element (in g/mol)

Front 6

To determine how many moles of a substance are present when you know the mass of a sample of that substance...

Back 6

You need to figure out how many times heavier the sample is in comparison to the mass of each mole (ie. divide by the molar mass)

Front 7

Percent composition (by mass)

Back 7

Expresses the relative contribution to the molecular mass of the compound by each element in the compound

Front 8

Percent composition and empirical formula both express...

Back 8

The relative amounts of the elements present in a compound (and therefore one can be determined from the other)

Front 9

The empirical formula is a ______ of the _______

Back 9

subunit, molecular formula

Front 10

The molecular mass is always an _______ of the empirical mass

Back 10

integer multiple

Front 11

Structural (constitutional) isomers

Back 11

Compounds consisting of the same collection of atoms, but the atoms are bonded in different ways within the 2 compounds. Because of this the compounds will have different properties

Front 12

Coefficients in chemical reactions tell us either...

Back 12

1. How many molecules of each type are involved OR
2. How many moles of molecules of each type are involved

Front 13

A chemical equation is balanced when...

Back 13

Equal numbers of each type of atom appear on both sides of the equation

Front 14

Coefficients vs. Subscripts

Back 14

Coefficients indicate relative numbers of molecules or moles of each species where subscripts show the relative numbers of atoms of a particular element that are present within a molecule

Front 15

Stoichiometry

Back 15

The analysis of the mole relationships among the reactants and products of a chemical reaction

Front 16

To perform stoichiometric calculations, we always work in...

Back 16

moles

Front 17

The number of moles of any species consumed or produced in a reaction is proportional to...

Back 17

its coefficient in the chemical equation

Front 18

If we combine the reactants in other than the _____, one reactant will be used up before the other(s) and at that point, the reaction will _____

Back 18

stoichiometric amounts, stop

Front 19

Limiting reactant/reagent

Back 19

The reactant which is completely consumed first and limits the amount of reaction that can occur

Front 20

Excess reagent

Back 20

Any reactant for which part of the starting amount remains unreacted

Front 21

Once the limiting reagent has been identified, it can be used to predict...

Back 21

1. How much product should form
2. How much of the excess reagent(s) should be consumed

Front 22

Theoretical Yield

Back 22

The maximum feasible amount of product produced (assuming reaction will run perfectly, will go to completion, and that you will be able to extract all of the product from the final reaction mixture)

Front 23

In real life, you _____ get the theoretical yield

Back 23

Never

Front 24

Actual Yield

Back 24

The amount of product that is obtained when the reaction is actually carried out

Front 25

The actual yield is always ______ the theoretical yield

Back 25

Less than

Front 26

Percent yield

Back 26

How close the actual yield is to the theoretical yield