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5
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A couple of strategies help:
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Balance any reactants or products that exist as the free element last
5
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Avogadro’s hypothesis: equal volume of all gases, when measured at the same
temperature and pressure, contain the same number of molecules
Here hydrogen and nitrogen combine to form ammonia
3 H2 (g) + N2 (g)  2NH3
Note ratio: 3 hydrogen combines with 2 nitrogen to form 1 ammonia (3:2:1)
5
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02 x 10^23
Mol (mol): is an amount of substance that contains the same number of elementary
units as there are atoms in exactly 12 g of carbon -12
Formula Masses: average mass of a formula unit relative to that of a carbon -12
atom
There are 6
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4 Molar Mass: Mole to Mass and Mass to Mole conversions:
Molar mass of a substance is the mass of one mole of that substance (equal to atomic
mass)
What is mass in gams of N2 is
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4 moles of n2 = 28 x
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2 g n2
Calculate number of moles of Na in 62
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 molar mass of Na is 23
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5
 x= 62
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763 mol
Stoichiometry: is the quantitative relationship between reactants and products in a
chemical reaction
Coefficients in balanced equation allow us to make statements such as
In consideration of: C3H8 + 5O2  3CO2 + 4H2O
 1 mol of C3H8 reacts with 5 mol of O2
 3 mol of CO2 is produced for every 1 mol of C3H8 that reacts
 4 mol of H2O is produced for every 3 mol of CO2 Produced
Stoichiometric factor: relates the amounts, in moles, of any two substances
involved in a chemical reaction
In consideration of: C3H8 + 5O2  3CO2 + 4H2O
 means 5 mol of O2 is needed to burn 1 mol of C3H8
 ratio is 1/5 or 5/1
When
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105 X 5/1 =
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5 Solutions: a solution is a homogeneous mixture of two or more substances
 substance being dissolved is the solute, substance doing the dissolving is
the solvent

Aqueous Solutions: those in which water is the solvent
Dilute Solution; one that contains a little bit of solute in lots of solvent
Concentrated Solution: one with much solute dissolved in relatively small quantity
of solvent
Molarity: (M): is the amount of solute, in moles, per liter of solution
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50 mol of NaCl in
enough water to produce 2
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5/2 = 1
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Balances do not display
unit sof moles , so we must convert
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L of solution?
 333g KHCO3 / 100 (total weight of KHCO3) = 3
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33 =10 =
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0 Liters of fuel
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5 g of NaCl dissolved in 425 g
of water?
25
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5 + 425= 5
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1 Solids, Liquids and Gases;
sublimation: substances that go directly from the solid state to the gaseous state

6
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1 Acids and Bases: Experimental Definitions
Acid; is a compound that:
 causes litmus indicator dye to turn red
 tastes sour
 dissolves active metals such as zinc and iron, producing hydrogen gas
 reacts with bases to form water and ionic compounds called salts
Base: is a compound that
 causes litmus indicator dye to turn blue
 tastes bitter
 feels slippery to the skin
 reacts with acids to form water and salts
Litmus: is an acid-base indicator
7
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 Chemists often indicate acids by writing H first (HCl, H2SO4)
Arrhenius Base: defined as a substance that releases hydroxide ions (OH-) in
aqueous solution
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These compounds
release hydroxide ions into water when the solid is dissolved in water
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1: write equations to show the ionization of nitric acid HNO3
in water
HNO3 (aq)  H+ (aq) + NO3- (aq)
Now show ionization of solid potassium hydroxide (KOH) in water
KOH (aq)  OH- (aq) + K+
Limitations on Arrhenius Theory:
 a simple free proton does not exist in water solution
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HNO3 (AQ) + H20  NO3 – (AQ) + H3O +
Ammonia is gas at room temperature- when dissolved in water, some of the
ammonia molecules react as shown:
NH3 (aq) + H20  NH4+ (aq) + OH- (aq)
Salts: formed from the neutralization reaction of acids and bases, are ionic
compounds composed of cations and anions
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3 Acidic and Basic Anhydrides:
Nonmetal Oxides: Acidic Anhydrides: acids are made by the reaction of nonmetal
oxides with water:

Here sulfur trioxide reacts with water to form sulfuric acid:
S03 + H2O  H2S04
Here carbon dioxide reacts with water to form carbonic acid
CO2 + H20  H2C03
In general, nonmetal oxides react with water to form acids
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It is very soluble in water
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Zinc Hydroxide, Zn(OH)2 is used as an absorbent in surgical dressings
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4 Strong and Weak Acids and Bases:
Strong Acid: Reacts completely with water
Hydrogen Chloride reacts with water, essentially no HCl remains




HCl + H2O  H3O+ + Cl- (No HCl remains)
We can simply write reaction as: HCl (aq)  H+ (aq) + Cl – (aq)

Weak Acid: reacts only slightly with water
HCN also ionizes in water: HCN (aq)  H+ (aq) + CN- (aq)
Double arrows indicates slight ionization (means ionization is reversible)
There are not a lot of strong: Most common are sulfuric, nitric and hydrochloric acid
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Most familiar strong based is sodium
hydroxide (NaOH) aka Lye
strong Base:
 sodium hydroxide (NaOH)
 potassium hydroxide (KOH)
 and hydroxides of all the other group 1A metals (except for Be OH2)
 group 2A hydroxides are also strong bases
Amphiprotic: a substance, such as water, can either donate a proton or accept a
proton
Most familiar weak base is ammonia (NH3)
7
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6 The PH Scale:
In solution, concentration of ions are measured in moles per liter
 a solution of 1 molar hydrochloric acid (1 M HCl) contains 1 mole of H+ ions
per liter
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02 x 10^23 hydrogen ions
The acidity of a particular solution can be described in moles per liter
PH Scale: 0 to 14, neutral point is 7
 below 7 = acidic
 above 7= basic
 PH of 4 means hydrogen ion concentration of 1x10^-4 mol/L
 PH of 2 means 1 x 10^ -2 mol/L

Bronted-Lowry Theory: a pair of compounds or ions that differ by one proton (H+)
is called a conjugate acid-base pair
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 If base NH3 accepts a proton, it becomes an acid NH4+ and now can donate a
proton)
 If acid HF donates a proton, it can become a base: F-)
Conceptual Example 7
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HBr: conjugate base is Br- (remove H)
B) HNO3: remove No3C) OH-: add OH2+
D) HS04-: add H2S04+
Buffer Solutions: maintains an essentially constant pH when small amounts of
strong acid or strong base are added
If we add a little strong base to this solution, it will react with weak acid:
OH- + HC2 H3 O2  H2O + C2 H3 O2If we add a little strong acid, it will react with the weak base:
H+ + C2H3O2-  HC2H3O2
Self Assessment Questions:
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HCN and CN2
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NH3/H3O+
3
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Added acid will react with: a
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Which of the following pairs could be combined to make a buffer?
C6H5COOH and C6H5COONa
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6
 due to pollutants in the air
Sulfur Dioxide is a precursor to acid rain
7
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CaCO3 is a common antacid ingredient
When a person with excess stomach acid takes antacid, the ph in stomach goes from
a low value to a value nearer 7
7
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Made by heating
limestone (CaCO3) to drive off Co2
CaCO3 (s) + heat  CaO (s) + CO2 (g)
32-35, 37, 43-48
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2 Water in Nature; 2% of the world’s water is drinkable ; 1% is frozen
Carbon dioxide reacts with water to form carbonic acid (H2CO3)
CO2 (g) + H2O (l)  H2CO3
Hard water; water that contains calcium, magnesium, or iron salts

Organic Matter; rain water dissolves matter from decaying plants & animals, small
amounts is good for the soil, however, large amounts will contaminate the
environment
Aerobic Decay (preferred but if you add too much organic matter to water you get
anaerobic decay)
Anaerobic Decay: these compounds smell or are dangerous
 if water is too warm or too polluted you get anaerobic decay

Self Assessment Questions;
1
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Energy to power the water cycle comes from: the sun
3
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The principal cations in water are: NA+ K+ CA
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3 Chemical and Biological Contamination:
Waterborne Disease: estimated 80% of all the worlds sickness is caused by
contaminated water
Cryptosporidium: a protozoa excreted in human and animal feces that resists
standard chemical disinfection
Acid Rain: acids formed from sulfur oxides and nitrogen oxides come down from
sky as rain, fog and snow
 corrodes metals, dissolves limestone and marble
Limestones can neutralize excess acid:
CaCO3 (S) + 2H+ (aq)  CA2+ + Co2 + h2o
Sewage and Dying Lakes:
Break down of organic matter by bacteria depletes dissolved oxygen in water
Aerobic Oxidation: occurs in presence of dissolved oxygen
 AO produced CO2, H2O and inorganic Ions

Biochemical Oxygen Demand (BOD): is the measure of amount of oxygen needed for
this degradation (aerobic)
 if BOD is high enough dissolved oxygen is depleted and no life can survive in
lake or stream
Flowing streams can recover (more oxygen) still streams can remain dead for years
Eutrophication: when algae dies they become organic waste and increases BOD
Anaerobic Decay: instead of oxidizing the organic matter, anaerobic bacteria
reduces it and Methane CH4 is formed
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4 industrial Water Use:
Cyanide is treated with chlorine and a base to form nitrogen gas, bicarbonate and
chloride ions
10OH- + 2 N- + 5Cl2  N2 2HCO3- + 10 Cl - + 4H20
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6 Making Water fit to Drink:
Water Treatment Plants: 2/3 water comes from treatment plants
Chemical Disinfection: chlorine is added to kill and remaining bacteria
Ozone (O3) can kill viruses while chlorine cannot , 100 times more effective in
killing polioviruses
other technologies;

Water contaminated with a variety of microorganisms can be purified by irradiation
with UV light
 disadvantage: no residual protection for drinking water and no taste/odor
control
 Limited effectiveness in turbid water and cost more than chlorine treatment
 Advantage: effective aginst cryptosporidium and no known by products
formed at levels that cause concern
Self-Assessment Questions:
A value of 3 ppm of dissolved oxygen means
3mg O / L H2O
in treatment of public water supplies, flocculation: helps remove dirt and bacteria
public water are aerated to improve taste
Chlorine is added to improve taste
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Some
aeration in this step and aerobic bacteria convert organic matter into inorganic
materials
Activated Sludge Method: combination of primary and secondary treatment
methods – pumps lots of air and creates flocs
 flocs filter and absorb contaminants
Advanced treatments:
Charcoal Filtration: charcoal absorbs organic molecules, charcoal can be
regenerated by heating to drive off the absorbed substances
Reverse Osmosis: pressure forces water through semipermeable membrance
leaving impurities behind
Phytoremediation: passage of effluent into large or natural or constructed lagoons
for storage, allowing for plants to remove metals and other contaminants



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