chem 101 week 4

Chem 101Powerpoints

Week ending 2/10/2012End of Chapter 2Chapter 3 Part 1

Naming Compounds that contain a Metal and a Non-Metal

• There are two types of Binary Ionic Compounds that result from the combination of an anion and a cation

I. Metal present forms only one type of cation

II. Metal present can form two or more cations with different charges

Type I Binary Ionic Compounds

• The cation is always named first and the anion second

• A simple cation (from a single atom) takes its name from the name of the element

ie. Na+ - sodium• A simple anion (obtained from a single atom) is

named by taking the first part of the element name (root) and adding the suffix –ide

ie. Cl- - chloride

Examples of Type I Compounds

• NaCl sodium chloride• KI potassium iodide• CaS calcium sulfide• CsBr cesium bromide• AlCl3 aluminum chloride

Type II Binary Ionic Compounds• Recall that the transition metals can form more than one type

of cation• When a transition metal is present you must specify which

cation is involved in the compound• Newer method uses roman numerals to specify the charge

on the cationie. FeCl2 -iron can form Fe+2 and Fe+3

-it must balance the anions charge -Cl- x 2 = -2 -therefore the cation must be Fe+2

- Iron(II) chloride

Older Method of Naming Type II Compounds

• The older method uses the endings –ic and –ous to indicate charge on the transition metal in a compound

• -ic – designates the ion with higher charge• -ous- designates the ion with the lower charge ie. Fe+2 -Ferrous and Fe+3 –Ferric FeCl2 – ferrous chloride

More Type II Names

• Fe2O3

• Fe must cancel the charge of the oxide• O-2(3) = 6• Therefore Iron (III) oxide or ferric oxide

• PbCl4

• Lead must cancel the charge on chloride• Cl-1 (4) = 4• Therefore lead (IV) chloride not lead (II)

Binary Compounds Containing Only Non-Metals

• Compounds that contain 2 non-metals or a non-metal and metalloid

• Rules for Naming Binary Compounds Containing Only Non-Metals

1. The first element in the formula is named first using the full element name

2. The second element is named as though it were an anion3. Greek prefixes are used to denote the numbers of atoms

present4. The prefix mono is never used for naming the first element

Greek prefixesNumber Prefixes

1 mono

2 di

3 tri

4 tetra

5 penta

6 hexa

7 hepta

8 octa

Examples

• CO • Compound of two non-metals • Carbon monoxide not monocarbon monoxide

• BF3 Boron trifluoride

• NO nitrogen monoxide• N2O5 dinitrogen pentoxide

Compounds that Contain Polyatomic Ions

• Compounds like NH4NO3

• Contain polyatomic ions – charged entities composed of several atoms bound together

-polyatomic ions are given special names that must be memorized in order to name compounds containing them

-most impt. Ones are in table 2.3 on pg. 61 and in handout

Oxyanions

• Series of polyatomic ions that contain an atom of a given element and a different number of oxygen atoms

• ClO-, ClO2-, ClO3

-, ClO4-

• SO32-, SO4

2-

Oxyanions

• When there are 2 members: -the one with the smaller number of oxygen

atoms ends with -ite -The one with the larger number of oxygen

atoms ends in –ate• When more than two members: -hypo (less than) is added as a prefix -per (more than) is added as a prefix

Oxyanions

• SO42- SO3

2-

sulfate sulfite

• NO3- NO2

-

nitrate nitrite

• ClO- ClO2- ClO3

- ClO4-

hypochlorite chlorite chlorate perclorate

Naming Compounds with Polyatomic Ions

• Similar to naming Binary Ionic compounds• Must learn to recognize the common

polyatomic ions• When the polyatomic ion is combined with a

transition metal, a roman numeral is required to specify cation charge

Compounds with Polyatomics and Oxoanions

– Na2SO4

sodium sulfate– KNO3

potassium nitrate– Mn(OH)2

manganese (II) hydroxide– Na2SO3 sodium sulfite– NH4Cl ammonium chloride

Writing Chemical Formulas from Names

• Thus far we have focused on determining a compounds systamatic name from a chemical formula

• Being able to reverse the process is crucial!• Laboratory procedures describe compounds by name

yet reagent jars typically show the formula only• It is essential that you be able to get the formula of a

compound from its name!

To write chemical formulas from names

• **it is essential to learn the name, composition and charge of the common polyatomic ions

• if you do not recognize these ions by formula and by the name you will not be able to write the compounds name given its formula or the compounds formula given its name

• Must also learn the names of the common acids

Acids

• When dissolved in water certain molecules produce hydrogen ions H+ (protons)

• Such molecules are called acids• Acids have a sour taste and turn blue litmus

red• Acids can be viewed as a molecule with one or

more H+ ions attached to an anion

Naming Acids

• An acids name will depend on whether the anion part of the acid contains oxygen

Rules for Naming Acids

1. If the anion does not contain oxygen the acid is named using the prefix hydro- and the suffix –ic attached to the root name for the anion element followed by the word “acid”

2. When the anion contains oxygen the acid name is formed from the root name of the central element of the anion or the anion name with a suffix of –ic or –ous

–When the anion ends in –ate the suffix -ic or -ric is used –When the anion ends in –ite the suffix –ous is used

Naming Acids

HCl (g) hydrogen chlorideHCl(aq) hydrochloric acidHCN(aq) hydrocyanic acidH2S(aq) hydrosulfuric acidH2SO4(aq) sulfuric acid (sulfate)

H3PO4(aq) phosphoric acid (phosphate)

HC2H3O2(aq) acetic acid (acetate)HNO3(aq) nitric acid (nitrate)H2SO3(aq) sulfurous acid (sulfite)HNO2 (aq) nitrous acid (nitrite)

Oxyacids

• Acids formed from oxyanions• To name oxyacids we use Rule #2 -ate → -ic or –ric -ite → -ous

Acid Anion Name HClO4 perchlorate Perchloric acid

HClO3 chlorate Chloric acid

HClO2 chlorite Chlorous acid

HClO Hypochlorite Hypochlorous acid

Final Note

• Thus far we have focused on determining a compounds systamatic name from its chemical formula

• REVERSING THE PROCESS IS CRUCIAL! –laboratory procedures describe compounds by

name, yet reagent jars typically show the formula only

–it is essential that you be able to write the formula of a compound from its name

A base can be defined as a substance that yields hydroxide ions (OH-) when dissolved in water.

NaOH sodium hydroxide

KOH potassium hydroxide

Ba(OH)2 barium hydroxide

2.7

Hydrates are compounds that have a specific number of water molecules attached to them.

BaCl2•2H2O

2.7

LiCl•H2O

MgSO4•7H2O

Sr(NO3)2 •4H2O

barium chloride dihydrate

lithium chloride monohydrate

magnesium sulfate heptahydrate

strontium nitrate tetrahydrate

CuSO4•5H2O CuSO4

2.7

Organic chemistry is the branch of chemistry that deals with carbon compounds

C

H

H

H OH C

H

H

H NH2 C

H

H

H C OH

O

methanol methylamine acetic acid

2.7

Functional Groups

Chapter 3

Part 1

Mass Relationships in Chemical Reactions

Chapter 3

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

By definition: 1 atom 12C “weighs” 12 amu

On this scale

1H = 1.008 amu

16O = 16.00 amu

Atomic mass is the mass of an atom in atomic mass units (amu)

Micro Worldatoms & molecules

Macro Worldgrams

3.1

Natural lithium is:

7.42% 6Li (6.015 amu)

92.58% 7Li (7.016 amu)

7.42 x 6.015 + 92.58 x 7.016100

= 6.941 amu

3.1

Average atomic mass of lithium:

Average atomic mass (6.941)

© 2009, Prentice-Hall, Inc.

Formula Weight (FW)• A formula weight is the sum of the atomic

weights for the atoms in a chemical formula.

• So, the formula weight of calcium chloride, CaCl2, would be

Ca: 1(40.1 amu) + Cl: 2(35.5 amu)

111.1 amu

• Formula weights are generally reported for ionic compounds.

Formula mass (formula weight) is the sum of the atomic masses (in amu) in a formula unit of an ionic compound.

1Na 22.99 amu1Cl + 35.45 amuNaCl 58.44 amu

For any ionic compound

formula mass (amu) = molar mass (grams)

1 formula unit NaCl = 58.44 amu1 mole NaCl = 58.44 g NaCl

3.3

NaCl

Do You Understand Formula Mass?

What is the formula mass of Ca3(PO4)2 ?

3.3

1 formula unit of Ca3(PO4)2

3 Ca 3 x 40.08

2 P 2 x 30.978 O + 8 x 16.00

310.18 amu

© 2009, Prentice-Hall, Inc.

Molecular Weight (MW)

• A molecular weight is the sum of the atomic weights of the atoms in a molecule.

• For the molecule ethane, C2H6, the molecular weight would be

C: 2(12.0 amu)

30.0 amu+ H: 6(1.0 amu)

Molecular mass (or molecular weight) is the sum ofthe atomic masses (in amu) in a molecule.

SO2

1S 32.07 amu2O + 2 x 16.00 amu SO2 64.07 amu

For any molecule

molecular mass (amu) = molar mass (grams)

1 molecule SO2 = 64.07 amu

1 mole SO2 = 64.07 g SO2 3.3

© 2009, Prentice-Hall, Inc.

Percent Composition

One can find the percentage of the mass of a compound that comes from each of the elements in the compound by using this equation:

% element =

(number of atoms)(atomic weight)

(FW of the compound)

x 100

© 2009, Prentice-Hall, Inc.

Percent Composition

So the percentage of carbon in ethane is…

%C =(2)(12.0 amu)

(30.0 amu)

24.0 amu

30.0 amu= x 100

= 80.0%

© 2009, Prentice-Hall, Inc.

Moles

© 2009, Prentice-Hall, Inc.

Avogadro’s Number

• 6.02 x 1023

• 1 mole of 12C has a mass of 12 g.

© 2009, Prentice-Hall, Inc.

Molar Mass

• By definition, a molar mass is the mass of 1 mol of a substance (i.e., g/mol).– The molar mass of an element is the mass number

for the element that we find on the periodic table.– The formula weight (in amu’s) will be the same

number as the molar mass (in g/mol).

© 2009, Prentice-Hall, Inc.

Using Moles

Moles provide a bridge from the molecular scale to the real-world scale.

© 2009, Prentice-Hall, Inc.

Mole Relationships

• One mole of atoms, ions, or molecules contains Avogadro’s number of those particles.

• One mole of molecules or formula units contains Avogadro’s number times the number of atoms or ions of each element in the compound.

Molar mass is the mass of 1 mole of in gramseggsshoes

marblesatoms

1 mole 12C atoms = 6.022 x 1023 atoms = 12.00 g

1 12C atom = 12.00 amu

1 mole 12C atoms = 12.00 g 12C

1 mole lithium atoms = 6.941 g of Li

For any element

atomic mass (amu) = molar mass (grams)

3.2

One Mole of:

C S

Cu Fe

Hg

3.2

1 amu = 1.66 x 10-24 g or 1 g = 6.022 x 1023 amu

1 12C atom12.00 amu

x12.00 g

6.022 x 1023 12C atoms=

1.66 x 10-24 g1 amu

3.2

M = molar mass in g/mol

NA = Avogadro’s number

x 6.022 x 1023 atoms K1 mol K

=

Do You Understand Molar Mass?

How many atoms are in 0.551 g of potassium (K) ?

1 mol K = 39.10 g K

1 mol K = 6.022 x 1023 atoms K

0.551 g K 1 mol K39.10 g K

x

8.49 x 1021 atoms K

3.2

Do You Understand Molecular Mass?

How many H atoms are in 72.5 g of C3H8O ?

1 mol C3H8O = (3 x 12) + (8 x 1) + 16 = 60 g C3H8O

1 mol H = 6.022 x 1023 atoms H

5.82 x 1024 atoms H

3.3

1 mol C3H8O molecules = 8 mol H atoms

72.5 g C3H8O1 mol C3H8O60 g C3H8O

x8 mol H atoms

1 mol C3H8Ox

6.022 x 1023 H atoms1 mol H atoms

x =

KE = 1/2 x m x v2

v = (2 x KE/m)1/2

F = q x v x B3.4

Ligh

t

Ligh

t

Hea

vy

Hea

vy

Percent composition of an element in a compound =

n x molar mass of elementmolar mass of compound

x 100%

n is the number of moles of the element in 1 mole of the compound

C2H6O

%C =2 x (12.01 g)

46.07 gx 100% = 52.14%

%H =6 x (1.008 g)

46.07 gx 100% = 13.13%

%O =1 x (16.00 g)

46.07 gx 100% = 34.73%

52.14% + 13.13% + 34.73% = 100.0%

3.5

3.5

Percent Composition and Empirical FormulasDetermine the empirical formula of a compound that has the following percent composition by mass: K 24.75, Mn 34.77, O 40.51 percent.

nK = 24.75 g K x = 0.6330 mol K1 mol K

39.10 g K

nMn = 34.77 g Mn x = 0.6329 mol Mn1 mol Mn

54.94 g Mn

nO = 40.51 g O x = 2.532 mol O1 mol O

16.00 g O

3.5

Percent Composition and Empirical Formulas

K : ~~ 1.00.6330

0.6329

Mn : 0.6329

0.6329= 1.0

O : ~~ 4.02.532

0.6329

nK = 0.6330, nMn = 0.6329, nO = 2.532

KMnO4

3.6

g CO2 mol CO2 mol C g C

g H2O mol H2O mol H g H

g of O = g of sample – (g of C + g of H)

Combust 11.5 g ethanolCollect 22.0 g CO2 and 13.5 g H2O

6.0 g C = 0.5 mol C

1.5 g H = 1.5 mol H

4.0 g O = 0.25 mol O