chem unit5
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Back to Moles
• • number of atoms in exactly 12 grams carbon-12
Avogadro’s Number• There are 6.02 x 1023 particles in a
mole of any substance.
Molar Mass
• Mass of one MOLE of pure substance
• Helium: 4.00 grams -------> 4 grams per mole
• Lithium 6.94 grams ---------> 6.94 grams per mole
• Mercury 200.59 grams -------> 200.59 grams per mole
0.1 Moles of Uranium
•(0.1 moles) x 238 grams/mole
= 23.8 grams
0.1 moles Uranium
•How many atoms?
• 6.022 x 1023 atoms/mole x 0.1 moles
= 6.022 x 1022 atoms
Molecules
•5 moles of CO2
= 5 moles x 6.022 x 1023 molecules/mole
= 3.1 x 1024 molecules of CO2
Molar Mass
•Mass in grams of one moleof the substance
CO2: mass C + 2 (mass O)
= 12 + 2(16) = 44 grams
Mass -> Moles
•Converting from g to moles:
For 112 grams of C2H4:
Grams of SubstanceGrams of
Substance Molar mass MOLES
Mass -> Moles•Converting from g to moles:
For 112 grams of C2H4:
112 g x 1 mole/28 g = 4 moles
Grams of SubstanceGrams of
Substance Molar mass MOLES
Moles -> Molecules• Converting from moles to Molecules
For 4 moles of C2H4:4 moles x 6.02 x 1023 molecules/mole = 2.41 x 1024
molecules
MolesMolesAvogadro’s Number molecules
Law of Definite Proportions
• Joseph Proust
• Regardless of the source, a compound always has the same proportion of elements
Law of Definite Proportions
•Copper (II) Carbonate
CuCO3 -> Copper + Carbon + Oxygen
51.36% 9.72% 38.85%
Percent Composition
•CO CO2
28 g/mole 44 g/mole
C: 12/28 = 42.86% C: 12/44 = 27.27%O: 16/28 = 57.14% O: 32/44 = 72.73%
Two different compound with different percentcompositions and different properties
Empirical Formula
• Smallest whole number ratio of atoms in a compound
• CaffeineMolecular formulaC8H10N4O2
Empirical formulaC4H5N2O
Percent Composition -> Empirical Formula
•Vinegar
•C: 40%H: 6.67%
•O: 53.33%
Percent Composition -> Empirical Formula
•Vinegarassume 100 g
C: 40 gramsH: 6.67 gramsO: 53.33 grams
Percent Composition -> Empirical Formula
C: 40 g x 1mole/12g = 3.33 moles
H: 6.67 g x 1 mole/1g = 6.67 moles
O: 53.33 g x 1 mole/16 g = 3.33 moles
Percent Composition -> Empirical Formula
C: 40 g x 1mole/12g = 3.33 moles
H: 6.67 g x 1 mole/1g = 6.67 moles
O: 53.33 g x 1 mole/16 g = 3.33 moles
Empirical Formula:
CH2O
Percent Composition -> Empirical Formula
C: 40 g x 1mole/12g = 3.33 moles
H: 6.67 g x 1 mole/1g = 6.67 moles
O: 53.33 g x 1 mole/16 g = 3.33 moles
Actual Formula:
C2H4O2
Percent Composition -> Empirical Formula
C: 40 g x 1mole/12g = 3.33 moles
H: 6.67 g x 1 mole/1g = 6.67 moles
O: 53.33 g x 1 mole/16 g = 3.33 moles
Actual Formula:
C2H4O2
Empirical Formula-> Molecular Formula
Empirical Formula: CH2O
Molecular Formula: C2H4O2
Molecular Formula is a whole number multiple of empirical formula
Empirical Formula-> Molecular Formula
Butyric Acid = butter flavor Empirical formula = C2H4O
Molar mass = 88 g/mole
Molecular formula =
Empirical Formula-> Molecular Formula
Butyric Acid = butter flavor Empirical formula = C2H4O
Molar mass = 88 g/mole Mass of emp. formula = 44 Molecular formula =
Empirical Formula-> Molecular Formula
Butyric Acid = butter flavor Empirical formula = C2H4O
Molar mass = 88 g/mole Mass of emp. formula = 44 Molecular formula = C4H8O2
Formula -> Percent Composition
Empirical formula Butyric Acid: C2H4O
Molar mass C x 2 = 12 x 2 = 24 Molar mass H x 4 = 1 x 4 = 4
Molar mass O = 16
44 g/mole
Formula -> Percent Composition
Empirical formula Butyric Acid: C2H4O
C = 24/44 = 0.545 = 54.5% H = 4/44 = 0.091 = 9.1%
O = 16/44 = 0.364 = 36.4%
Chemical VS. Physical Change
Physical Chemical
Chemical VS. Physical Change
Physical Chemical• change in phase • atomic rearrangement
• change in appearance, • energy change
shape (absorption or release)
Chemical Equations
Shorthand symbols:(s), (l), (g) = solid, liquid, gas phases
(aq) = substance in aqueous solution
--> = reaction event AX -> BY
<=> reaction in equilibrium (reversible)
Chemical Equations
Silicon tetrachloride and water react to form silicon dioxide and hydrochloric acid
Chemical Equations
Silicon tetrachloride and water react to form silicon dioxide and hydrochloric acid
SiCl4 + H2O SiO2 + HCl
Reactants Products
Chemical Equations
Silicon tetrachloride and water react to form silicon dioxide and hydrochloric acid
SiCl4 + 2 H2O SiO2 + 4 HCl
Balanced
Balancing Chemical Equations
Conservation of Matter:
H2 + O2 ---------------> H2O
Balancing Chemical Equations
Conservation of Matter:
2 H2 + O2 ---------------> 2 H2O
Balancing Chemical Equations
propane gas + oxygen gas -> carbon dioxide gas + water vapor
Balancing Chemical Equations
propane gas + oxygen gas -> carbon dioxide gas + water vapor
C3H8(g) O2(g) -> CO2(g) H2O(g)
Balancing Chemical Equations
propane gas + oxygen gas -> carbon dioxide gas + water vapor
C3H8(g) O2(g) -> 3 CO2(g) H2O(g)
Balancing Chemical Equations
propane gas + oxygen gas -> carbon dioxide gas + water vapor
C3H8(g) O2(g) -> 3 CO2(g) 4 H2O(g)
Balancing Chemical Equations
RULES:
•Identify reactants and products
•Count atoms
•Insert coefficients
•Check your work
Balancing Chemical Equations
aluminum metal and iron (II) nitrate react to form aluminum nitrate and iron metal
Balancing Chemical Equations
aluminum metal and iron (II) nitrate react to form aluminum nitrate and iron metal
Al + Fe(NO3)2 Al(NO3)3 + Fe
Balancing Chemical Equations
aluminum metal and iron (II) nitrate react to form aluminum nitrate and iron metal
2 Al + 3 Fe(NO3)2 2 Al(NO3)3 + 3 Fe
Balanced
Types of Chemical Equations
1. Combustion
2. Synthesis
3. Decomposition
4. Single Displacement
5.Double Displacement
6.Acid – Base*
Combustion
Reaction of a carbon-based compound with oxygen
2 C4H10 + 13 O2 8 CO2 + 10 H2O
butane
Combustion
Alcohol lamp
C2H5OH + 3 O2 2 CO2 + 3 H2O
Synthesis
Forming a single compound from two or more reactants
H2 + O2 H2O
Synthesis
Forming a single compound from two or more reactants
2 Na + Cl2 2 NaCl
Decomposition
Breakdown of a single compound(Opposite of synthesis)
2 NaN3 2 Na + 3N2
Decomposition
Breakdown of a single compound(Opposite of synthesis)
NH4NO3 N2O + 2 H2O
Single Displacement
A single element reacts with a Compound and displaces another element from that compound
Zn + 2 HCl ZnCl2 + H2
Single Displacement
A single element reacts with a Compound and displaces another element from that compound
2 K + 2 H2O 2 KOH + H2
Activity Series
Element ReactivityK
CaNa
React with cold water and acids to replace hydrogen; react with oxygen to form oxides
MgAlZnFe
React with steam (not cold water) and acids to replace hydrogen; react with oxygen to form oxides
NiPb
Do not react with water; react with acids to replace hydrogen; react with oxygen to form oxides
H2
Cu React with oxygen to form oxides
AgAu Unreactive; form oxides only indirectly
Activity Series
What will happen if iron (steel wool) is added to a copper(II) sulfate solution?
Activity Series
Fe(s) + CuSO4 (aq) -> Cu(s) + FeSO4(aq)
Double Displacement
Two compounds exchange ions andForm new compounds
Pb(NO3)2 + KI PbI2(s) + 2 KNO3
Net Ionic Equations
When aqueous solutions are mixed, new ionic combinationsare made.
Mass and Charge must beconserved.
Na2SO4(aq) + Sr(NO3)2(aq) SrSO4(s) + 2 NaNO3(aq)
precipitate
Net Ionic Equations
Precipitate = insoluble solid thatSeparates from solution
Na2SO4(aq) + Sr(NO3)2(aq) SrSO4(s) + 2 NaNO3(aq)
precipitate
Net Ionic Equations
Na2SO4 - > 2 Na+ + SO42-
Sr(NO3)2 - > Sr2+ + 2 NO3-
NaNO3 - > Na+ + NO3-
Na2SO4(aq) + Sr(NO3)2(aq) SrSO4(s) + 2 NaNO3(aq)
precipitate
Net Ionic Equations
Na2SO4 - > 2 Na+ + SO42-
Sr(NO3)2 - > Sr2+ + 2 NO3-
NaNO3 - > Na+ + NO3-
2 Na+ + SO42- + Sr2+ + 2 NO3
- SrSO4(s) + 2 Na+ + 2 NO3-
spectator ions precipitate
Solubility Rules
All alkali metal and NH4+ salts are
soluble;
All nitrates (NO3) are soluble;
All Halides (F, Cl, Br, I) are solubleexcept Ag+ and Pb2+
Sulfates(SO4), except for Ca2+, Ba2+, Sr2+, Pb2+ are soluble
Carbonates (CO3) are insoluble except for alkali metal and NH4.
Net Ionic Equations
Li2CO3 + BaBr2 BaCO3 + 2 LiBr
Net Ionic Equations
Li2CO3 -> 2 Li+ + CO32-
BaBr2 -> Ba2+ + 2 Br-
Li2CO3 + BaBr2 BaCO3 + 2 LiBr
precipitate
Unit 5 Review
Molar Mass g <-> atoms/molecules <-> moles
Percent Composition Empirical and Molecular Formula
Chemical equations: Word Equations, Balancing