supplemental packet page 117. this is a chemical recipe for the decomposition of water by...
TRANSCRIPT
2 x 1 mole 2 x 1 mole 1 x 1 mole
by numbers by volume
Chemical Methodsfor counting amountsfor counting amounts
Physcisal Methods
COUNTING
2 H2O 2 H2 + 1 O2
by weighing
by balanced reaction
1 mole any gas = 22.4 L @ 0°C,1atm
1 pr = 21 doz = 12
1 case = 12 or 24
1 hand = 5 fingers
1 foot = 12 inches
1 gummy bear = 1 gram1 penny = 1 gram1 proton = 1 amu1 neutron = 1 amu1 hydrogen-1 atom = 1 amu
1 carbon-12 atom = 12 amu
1 mole = 6.02x10+23
anything anything
Avogadro'snumber
1 mole carbon-12 = 12 grams carbon-12 exactly
(6.02x10+23
) (6.02x10+23
)
numbers to amountsby weighing
2 molecule 2 molecules 1 molecule
2 x A number 2 x A number 1 x A number
2 x 6.02x10+23 2 x 6.02x10
+23 1 x 6.02x10+23
multiply through by A number
A number equals Avogadro's #
Avogadro's # equals 1 mole
2 x 18 grams 2 x 2 grams 1 x 32 grams
count by weighing
H2O H2 O2per
1 moleper
1 moleper
1 moleO2H2H2O
molar massesdefined
the eletrolysis of 36 grams of water will produce 4 grams of hydrogen and 32 grams oxygen
Supplemental packet page 117
2 x 1 mole 2 x 1 mole 1 x 1 mole
Chemical Methodsfor counting amounts
2 H2O 2 H2 + 1 O2
by balanced reaction
2 molecule 2 molecules 1 molecule
2 x A number 2 x A number 1 x A number
2 x 6.02x10+23 2 x 6.02x10
+23 1 x 6.02x10+23
multiply through by A number
A number equals Avogadro's #
Avogadro's # equals 1 mole
2 x 18 grams 2 x 2 grams 1 x 32 grams
count by weighing
H2O H2 O2per
1 moleper
1 moleper
1 moleO2H2H2O
This is a chemical recipe forthe decomposition of waterby electrolysis.
productsreactants
What did John Dalton in 1808 have to say about chemical reactions?
1. Chemical reactions involve just the simple rearrangement of atoms.
2. Atoms are conserved in a chemical reaction.In other words, atoms are not created nor destroyed in chemical reaction.
Is this true for the decomposition of water by electrolysis?
2 H2O 2 H2 + 1 O2
Write the following opposite supplemental packet page 106
2 H2O 2 H2 + 1 O2
1. Chemical reactions involve just the simple rearrangement of atoms.
2. Atoms are conserved in a chemical reaction.In other words, atoms are not created nor destroyed in chemical reaction.
This ture for the below decomposition of water by electrolysis.
H HO
OHH
O
O
H H
HH
4 hydrogen atoms 4 hydrogen atoms
2 oxygen atoms 2 oxygen atoms
Let’s see if John Dalton had assumed correctly.
2 H2O 2 H2 + 1 O2
by balanced reaction
2 molecule 2 molecules 1 molecule
multiply through by A number
2 x A number 2 x A number 1 x A number
A number equals Avogadro's #
2 x 6.02x10+23 2 x 6.02x10
+23 1 x 6.02x10+23
Avogadro's # equals 1 mole
2 x 1 mole 2 x 1 mole 1 x 1 mole
count by weighing
2 x 18 grams 2 x 2 grams 1 x 32 gramsH2O H2 O2per
1 moleper
1 moleper
1 moleO2H2H2O
36 grams H2O produces 4 grams H2 and 32 grams O2
Stoichiometry supplemental packet page 117
2 H2O 2 H2 + 1 O2
by balanced reaction
2 molecule 2 molecules 1 molecule
multiply through by A number
2 x A number 2 x A number 1 x A number
A number equals Avogadro's #
2 x 6.02x10+23 2 x 6.02x10
+23 1 x 6.02x10+23
Avogadro's # equals 1 mole
2 x 1 mole 2 x 1 mole 1 x 1 mole
count by weighing
2 x 18 grams 2 x 2 grams 1 x 32 gramsH2O H2 O2per
1 moleper
1 moleper
1 moleO2H2H2O
⊕
9 voltbattery
OOH H
HH
H HOO
HH
9 voltbattery
(source of electrons)
#
#
H H
O
O
HH
ElectrolysisDr.Gergens - SD Mesa College
Stoichiometry supplemental packet page 118
Reduction is Gain, RIG
2 H2O 2 H2 + 1 O2(l) (g) (g)
0 0
2H+ + 2e- H20
The battery supplies those electrons⊕
9 voltbattery
Remember hydrogen ions’s favorite charge inits combined state is:
H+
⊕
9 voltbattery
2 H2O 2 H2 + 1 O2(l) (g) (g)
Then what happened the oxygen atom in water?
0 0
So oxide ion must have lost electrons
O2- O0 + 2e- Lost electrons in the electrolysis are attractedTo the positive ca hode⊕
Oxidation is loss of electrons, OIL
Remember oxygen ion’s favorite charge inits combined state is:
O2-
2-
O2- O0 + 2e- 2H+ + 2e- H2
0 Oxidation is Loss, OIL
Reduction is Gain, RIG
REDOX,is about the exchange of electrons.
Summary:
21 H2 + 1 O21 H2O
2 H2O 2 H2 + 1 O2(l) (g) (g)
0 0
Take the summation of both half-reactions affords the overall rxn below
Equilibrium
off-balanced(unequal)
reactant to product Equilibrium
balance Precipitation saturation
(solid formation)
gas formation
Up & DownReflux
likeacid reflux
(heart burn)
Supplemental packet page 106
The chemical equation is the shorthand notation for a chemical reaction.
ProductsReactantsreact to produce
Law of Conservation of Mass - Matter cannot be gained or lost in the process of a chemicalreaction. The law of conservation of mass states that we must have a balanced equation.List five factors involved in the construction of an equation or "chemical recipe."1.The identity of products and reactants must be specified.
2.Reactants are written to the left of the reaction arrow (---->) and products to the right.
3.The physical state of reactants and products is shown is parentheses;
(s), (l), (g), (aq). Recall (aq) means aquesous solutoins (solute + solvent)
4.The symbol Δ .over the reaction arrow means that heat energy is necessary for the reaction to occur
5. .The equation must be balanced
Supplemental packet page 106
Steps for balancing a chemical equation
Step 1: Count the number of atoms of each element on both the product and reactant side.Step 2: Determine which atoms are not balanced.Step 3: Balance one atom at a time, using coefficients. Start with atoms that appear
only once in the reactants and only once in the products. Usually leaveHydrogen atoms followed by Oxygen atoms until last.
Step 4: After you believe that you have successfully balanced the equation, repeat Step1, to be certain that mass conservation has been achieved.
Note:
Na2Cl2 )XDO NOT Change subscripts in a molecular formula (i.e., 2 NaCl
Don’t do this!!!!
Supplemental packet page 106
2 Mg + 1 O2 2 MgO 2 21
2 Mg + 1 O2 2 MgO
In balancing, we would like the lowest whole number molar ratio. Where the number out in front is called a molar coefficient.
Write this into our notes
2 Mg + 1 O2 2 MgO
2 Mg + 1 O2 2 MgO 1 12 •
But what if an individual balanced the magnesium first?
12
The reaction is balanced, BUT there is a fractional molar coefficient.We must remove the fraction by multiplying through by 2.
2 1 2
2 • 1 2 • 12
2 • 1
In my opinion, the following is the easiest way to balance, if you:1) always balance oxygens last;
2) then multiply by factor of 2, to remove any fractional molar coefficient that might be present in the balanced reaction.
32
1 Fe2O3 2 Fe + O22 132
32
1 Fe2O3 2 Fe + O2
2 •
4 3 2
2 • 2 2 • 32
2 • 1
Note: We are going for the lowest whole numberMolar coefficient ratio
2 Mg + 1 O2 2 MgO
Finally, name the compounds and give physical states.
(s)
magnesium metalsolid
(g)
oxygengas
(s)
magnesium oxidesolid ionic salt
32
1 Fe2O3 2 Fe + O24 3 2(s)
iron metalsolid
(g)
oxygengas
(s)
iron (III) oxidesolid TM ionic salt
1CO2 + 2H2O 1CH4 + 2O2 Always balance oxygens last
1 1
1 • O2 + 2 • 1O
? • O2 = 4
2?2
2 + 2 = 4
Combustion of methane gas
? • O2 = 7
72
2CO2 + 3H2O 1C2H6 + O2
72
2CO2 + 3H2O 1C2H6 + O2 Always balance oxygens last
1 2
2 • O2 + 3 • 1O
4 + 3 = 7
3?722
2 • 1 2 • 72
2 • 2 2 • 3
2 7 4 6
Combustion of ethane gas
1CO2 + 2H2O 1CH4O + 3O2 Always balance oxygens last
1 1
1 • O2 + 2 • 1O
2 + 2 = 4
2?
1 • O + ? • O2 = 4
1 + ? • 2 = 4 Now solve for “?”
? • 2 = 3-1 -1 Substract one from each side
23
? =23
2 2 Divide each side by 2
Combustion of methanol liquid
1CO2 + 2H2O 1CH4 + 2O2O
1CO2 + 2H2O 1CH4O + 3O21 1 2?232
2 x 1 2 x 32
2 x 1 2 x 2
2 3 2 4
Combustion of methanol liquid
6CO2 + 6H2O1C6H12O6 + 6O2 Now balance the combustion of glucose (blood sugar)
Always balance oxygens last
1 6
1 • O2 + 6 • 1O
1•O6 + ? • O2 = 18
6?6
12 + 6 = 18
6 + ? • 2 = 18 Now solve for “?”
? • 2 = 12
-6 -6 Substract 6 from each side
? = 6
2 2 Divide each side by 2
Combination - Synthesis - PHOTOSYNTHESIS
6 16 6CO2 + H2O C6H12O6 + O2chlorophyllcatalyst
C2H6O + O2 CO2 + H2O
CH2O + O2 CO2 + H2O
combustion
1 2 33
1 1 11
CH4O + O2 CO2 + H2O2 2 43
2x CH4O + O2 CO2 + H2O1 1 23__
2
Don’t leave as a fraction, multiply through by 2Combustion of methanol, CH4O
Combustion of ethanol, C2H4O
Combustion of formaldehyde, CH2O
What reactant was oxidized? What reactant was reduced?
C 4+ O 2–O
2–
Ionic salt transfer reactions in aqueous solution
Ionic salt solubility in water
All group I salts soluble, Li,Na,KAll nitrate salts solubleAll ammonium salts soluble,NH4
+
Driving forces for ion transfer, a force that makes the reaction go.
Physical state formations:If a solid formsIf a liquid formsIf a gas forms
Evidence for chemical change, ∆Color change (tricky)Heat evolved (tricky)
precipitation saturation (solids)If a liquid forms (heat evolved)If a gas forms (bubbles, odor)
A+B- (aq) + C+D- (aq) AD(?) + BC(?)
you’ll need to determine statebased on some rules
Ionic salt transfer reactions in aqueous solutionA+B- (aq) + C+D- (aq) AD(?) + BC(?)
Common sense tells us to mix ionic solutions in order to have an reaction to occur. (we are not going to mix for the sake of mixing)
Use of common sense tells us that,An acids mixed with a base (antacid) causes a neutralization.
H+A- (aq) + M+OH- (aq) H2O (l) + MA(?)Use of common sense tells us that,An acids mixed with carbonate (HCO3
-) produces CO2 water and salt
H+A- (aq) + NaHCO3 (aq) H2O(l) + NaA(aq)
CO2 (g)
A+B- (aq) + C+D- (aq) AD(?) + BC(?)
silver (I) cloride + sodium nitratesilver (I) nitrate + sodium chloride silver (I) cloride + sodium nitratesilver (I) nitrate + sodium chloride Say the product namessilver (I) nitrate + sodium chloride silver (I) chloride + sodium nitrateNow write the ions associated with each substance
Ag+ (NO3)– Na+ Cl- Ag+ (NO3)–Na+Cl-
Now write formuals for the products
AgCl + NaNO3
Identify physical state in aqueous solution
Solubility rules need to be applied.
(s) (aq)
monatomic ions oxy ions, XO–
suffix -atessuffix -ides
isoelectronic chargesPO4
3- SO4
2- ClO4
1-
BO33-
CO32-
NO3-
C4±
N-3 O
2- F
1-
P-3 S
2- Cl
1-
MUST learn X— charges!!!
carbide ion
X- charges
nitride ionoxide ionfluoride
phosphide ionsulfide ionchloride ion
phosphate ionsulfate ionperchlorate ion
borate ioncarbonate ionnitrate ion
Feo Fe 2+ + 2e- OxidationOIL
1 1
Fe(s) + Cl2(g) FeCl2 (s) 1 11
Combination - Synthesis (the REDOX process defined)
Analyzing the half reactions
Cl2o + 2e- 2Cl – Reduction
RIG
Fe 2+Cl –
Cl –
iron (II) chloridechlorine gasiron metal forms>plus
Feo Fe 2+ + 2e- OxidationOIL
Cl2o + 2e- 2Cl – Reduction
RIG
1 1
11
Fe(s) + Cl2(g) FeCl2 (s) 1 11
Combination - Synthesis (the REDOX process defined)
Analyzing the half reactions
Fe 2+Cl –
Cl –
iron (II) chloridechlorine gasiron metal forms
combining both half reactions
1 Fe(s) + 1 Cl2(g) 1 FeCl2 (s)
the electrons on the reactant side cancel the electrons on the product side
2 Mg + 1 O2 2 MgO
What reactant was oxidized?
(s)
magnesium metalsolid
(g)
oxygengas
(s)
magnesium oxidesolid ionic salt
What reactant was reduced?
Mg O O2O Mg 2+ O
2–
Mgo lost electrons
Oxygen gained electrons
What reactant was oxidized?
32
1 Fe2O3 2 Fe + O24 3 2(s)
iron metalsolid
(g)
oxygengas
(s)
iron (III) oxidesolid TM ionic salt
What reactant was reduced?
Fe 3+ O 2–
Fe 3+ O 2–
O 2–
Fe O
Iron metal lost electrons
O2O
Oxygen gained electrons
Combustion of methanol in PLASTIC BOTTLE
REDOX MID-TERM
Fe + Cl2 FeCl21 11
2 H2O 2 H2 + 1 O2
H HO
OHH
O
O
H H
HH
4 hydrogen atoms 4 hydrogen atoms
2 oxygen atoms 2 oxygen atoms
SOLUBILITY in aqueous solutions
BATTERY DEMO
2 x 1 mole 2 x 1 mole 1 x 1 mole
by numbers by volume
Chemical Methodsfor counting amountsfor counting amounts
Physcisal Methods
COUNTING
2 H2O 2 H2 + 1 O2
by weighing
by balanced reaction
1 mole any gas = 22.4 L @ 0°C,1atm
1 pr = 21 doz = 12
1 case = 12 or 24
1 hand = 5 fingers
1 foot = 12 inches
1 gummy bear = 1 gram1 penny = 1 gram1 proton = 1 amu1 neutron = 1 amu1 hydrogen-1 atom = 1 amu
1 carbon-12 atom = 12 amu
1 mole = 6.02x10+23
anything anything
Avogadro'snumber
1 mole carbon-12 = 12 grams carbon-12 exactly
(6.02x10+23
) (6.02x10+23
)
numbers to amountsby weighing
2 molecule 2 molecules 1 molecule
2 x A number 2 x A number 1 x A number
2 x 6.02x10+23 2 x 6.02x10
+23 1 x 6.02x10+23
multiply through by A number
A number equals Avogadro's #
Avogadro's # equals 1 mole
2 x 18 grams 2 x 2 grams 1 x 32 grams
count by weighing
H2O H2 O2per
1 moleper
1 moleper
1 moleO2H2H2O
molar massesdefined
the eletrolysis of 36 grams of water will produce 4 grams of hydrogen and 32 grams oxygen