Ch. 3 Molecules and Compounds

hydrogen gas H2

explosive gas

oxygen O2

must be present for combustion to occur

Water H2O

a liquid under normal conditions with a much higher boiling point than its constituents

When two or more elements combine to form a compound

an entirely new substance is formed

chemical bonds

compounds are composed of atoms held together by chemical bonds

Ionic bonds

metal atoms lose electrons to become cations (+)

Nonmetal atoms gain electrons to form anions (-)

the electrostatic attraction forms an ionic bond

covalent bonds

when a nonmetal bonds with another nonmetal or a metalloid, electrons are shared rather than transferred

results in the formation of a molecule

types of chemical formulas

molecular formula, empirical formula, structural formula

molecular formula

shows the actual number of atoms of each element present

empirical formula

shows the relative number of atoms of each element present

structural formula

uses lines to represent how the atoms are connected

Glucose molecular formula

molecular: C6H12O6

empirical: CH2O

Empirical formula of C4H8

CH2

Empirical formula of B2H6

BH3

Empirical formula of C5H12

C5H12

What part of the atom do you think the spheres in the molecular space filling models represent? How big would a superimposed nucleus be?

Each sphere represents the electron cloud of an atom. The nucleus would be too small to see

atomic elements

single atoms as the basic unit

molecular elements

naturally exist as molecules (H2, N2, O2, X2, P4, S8, Se6,7,8)

molecule

basic unit of a covalent compound

formula unit

basic unit of an ionic compound

Polyatomic ion

composed of a group of covalently bonded atoms with an overall charge

Carbonate, nitrate, sulfate, phosphate, ammonium, and hydroxide

Carbonate

CO3^2-

Nitrate

NO3^-

Sulfate

SO4^2-

Phosphate

PO4^3-

Ammonium

NH4^+

Hydroxide

OH^-

Xenon

atomic element

NiCl2

ionic compound

Bromine

molecular element

NO2

molecular compound

NaNO3

ionic compound

Fluorine

molecular element

N2O

molecular compound

Silver

atomic element

K2O

ionic compound

Fe2O3

ionic compound

molecular compound is composed of

2 nonmetals

ionic compound is composed of

metals and nonmetals

Which statement best summarizes the difference between ionic and molecular compounds?

molecular compounds contain highly directional covalent bonds, which results in the formation of molecules. Ionic compounds contain nondirectional ionic bonds, which result in the formation of ionic lattices

ionic compounds occur throughout the Earth’s crust as minerals

Limestone, CaCO3

Gibbsite, Al(OH)3

Soda Ash Na2CO3

Foods we eat

table salt, NaCl

calcium carbonate, CaCO3

potassium chloride, KCl

Ionic compounds are very stable because of?

the strong attraction between the (+) and (-) charges

ionic formulas

always contain positive and negative ions

sum of the charges in the chemical formula must be zero

a formula represents the smallest whole number ratio of atoms

Ionic compound formula for potassium and sulfur

K^+

K2S

S^2-

ionic compound formula for aluminum and nitrogen

Al^3+

AlN

N^3-

Naming ionic compounds

the cation is named first and the anion second with the ending -ide

some metals (transition metals) may have more than one form and special naming is used

Name Ag3N

Silver nitride

Formula for rubidium sulfide

Rb2S

Fe^2+

Iron (II) or ferrous

Fe^3+

Iron (III) or ferric

Cu^+

Copper (I) or cuprous

Cu^2+

Copper (II) or cupric

Sn^2+

Tin (II) or stannous

Sn^4+

Tin (IV) or stannic

Pb^2+

Lead (II) or plumbous

Pb^4+

Lead (IV) or plumbic

Name FeS

Iron (II) sulfide

Name PbCl4

Lead (IV) chloride

Formula for ruthenium(IV) oxide

RuO2

name Li2Cr2O7

lithium dichromate

name Sn(ClO3)2

Tin (II) chlorate

formula for cobalt (II) phosphate

Co3(PO4)2

hydrated ionic compounds

hydrates contain a specific number of water molecules associated with each formula unit

lattice waters are part of the molar mass

waters of hydration must be designated

\

naming molecular compounds

some have common names; H2O is water, NH3 is ammonia

the first element in the name will be the one more “metal like” of the nonmetals

prefixes - mono, di, tri, tetra, penta, hexa

NI3

nitrogen triiodide

PCl5

phosphorus pentachloride

P4S10

tetraphosphorus decasulfide

name N2O5

dinitrogen pentaoxide

formula for phosphorus tribromide

PBr3

The compound NCl3 is named nitrogen trichloride, but AlCl3 is simple aluminum chloride. Why?

NCl3 is a molecular compound

AlCl3 is a ionic compound

acids

molecules that release H+ ions when dissolved in water

naming binary acids

composed of hydrogen and a nonmetal

hydro + (base name of nonmetal + ic) + acid

name HI

hydroiodic acid

name HF

hydrofluoric acid

naming oxyacids

contain hydrogen and a oxyanion (polyatomic ions)

oxyanions ending with -ate: base name of the oxyanion + -ic acid

oxyanions ending with -ite: base name of the oxyanion + -ous acid

Name HC2H3O2 (aq)

oxyanion is acet**ate**

acid name is acetic acid

name HNO2 (aq)

oxyanion is nitrite

acid name is nitrous acid

formula for perchloric acid

HClO4

\
ClO4^- is perchlorate

SO2

sulfur dioxide

HClO4 (aq)

perchloric acid

CoF2

cobalt (II) fluoride

H2SO3 (aq)

sulfurous acid

formula mass of calcium nitrate

CaNO3^- = Ca(NO3)2

40.08

\+2(14.01 + 16.00(3))

=

164\.10 amu

calculate the number of ibuprofen molecules in a tablet containing 200.0 mg of ibuprofen (C13H18O2)

200\.0 mg (1 g/1,000 mg)(1 mol/206.31 g)(6.022 x 10^23/1 mol)= 5.838 x 10^20 molecules

what is the mas of a sample of water containing 3.55 x 10^22 H2O molecules

3\.55 x 10^22 molecules (1 mol/ 6.022 x 10^23)(18.02 g/1 mol)= 1.06 g H2O

mass percent composition

expression of how much of each element present in a compound

\
mass % of element = (mass of element in 1 mol of compound/mass of 1 mol of the compound) x 100

calculate the mass percent composition of oxygen in acetic acid (C2H4O2)

2(12.01) + 4(1.01) + 2(16.00) = 60.06

\
32/60.06 x 100 = 53.28%

calculate the mass percent composition of sodium in sodium oxide

2(22.99) + 16.00 = 61.98

\
45\.98/61.98 x 100 = 74.19%

what mass in grams of iron (III) oxide contains 58.7 g of iron? Iron (III) oxide is 69.94% iron by mass

58\.7 (100/69.94)= 83.9 g

when 22 g of sodium chloride is consumed, what mass of sodium was consumed? (NaCl= 39%)

22 (39/100) = 8.6 g

determine the mass of oxygen in a 7.2 g sample of Al2(SO4)3

Al2(SO4)3 = 342.17

O= 192

\
12(16.00) / 2(26.98) + 3(32.07) + 12(16.00) = 192/342.17

0\.561(7.2) = 4.0 g O

how many grams of carbon are present within 7.25 mL of butane? (C4H10) d=0.601

7\.25(0.601/1 mL)(1 mol/58.14)(4 mol C/1 mol)(12.01 g/1 mol) = 3.60 g C

The molecular formula for water is H2O. Which ratio can be correctly derived from this formula?

2 mol : 1 mol H2O

a sample produces 165 g carbon, 27.8 g hydrogen, and 220.2 g oxygen. calculate the empirical formula of the compound

165(1 mol/12.01) = 13.7/13.7= 1

27\.8(1 mol/1.01) = 27.5/13.7 = 2

220\.2(1 mol/16.00) = 13.8/13.7=1

\
CH2O

C 60.00%

H 4.48%

O 35.52%

Determine the empirical formula

60\.00(1mol/12.01)=4.996/2.22=2.25(4)=9

4\.48(1mol/1.01)=4.44/2.22=2(4)=8

35\.52(1mol/16.00)=2.22/2.22=1(4)=4

C9H8O4

C 75.69%

H 8.80%

O 15.51%

Determine the empirical formula

75\.69(1/12.01)=6.302/0.9694=6.5(2)=13

8\.80(1/1.01)=8.71/0.9694=9(2)=18

15\.51(1/16.00)=0.9694/0.9694=1(2)=2

\
C13H8O2

a compound has empirical formula CH and a molar mass of 78.11 g/mol. What is the molecular formula?

CH= 12.01 + 1.01= 13.02

78\.11/13.02=6

C6H6

A compound with the precent composition shown below has a molar mass of 60.10 g/mol. Determine the molecular formula

C 39.97%

H 13.41%

N 46.62%

39\.97(1/12.01)=3.328/3.328=1

13\.41(1/1.01)=13.28/3.328= 4

46\.62(1/14.01)=3.328/3.328=1

CH4N = 12.01+4(1.01)+14.01=30.06

60\.10/30.06=2

C2H8N2

Combustion analysis

empirical formula can be determined

particularly useful for compounds containing carbon and hydrogen

an unknown compound is burned in the presence of pure oxygen, all carbon is converted to CO2 and the hydrogen to H2O