chapter 2: antacids. antacids mixture are a compounds chemical formulas chemical formulas collision...
TRANSCRIPT
Chapter 2: Antacids
Antacids
MixtureMixture
Are a
CompoundsCompounds
ChemicalFormulas
ChemicalFormulas
Collision Theory
Collision Theory
Acids & BasesAcids & Bases
Chemical ReactionsChemical Reactions
Of differentSymbolizedwith
Some are
Balanced Chemical Equations
Balanced Chemical Equations
undergo
Symbolizedwith
Used in
Speed governed by
Antacids versus Acid Inhibitors
Acid InhibitorsAntacids
Neutralizes the acid currently in your system
Controls the amount of acid your body produces
There are two types of medicines you can use
Work quickly but your body will make more acid again
Long-term solution, but needs to build up in your system to be
most effective
Alka-Seltzer ®, Rolaids ®, Tums ®, Malox ®, Mylanta ®
Tagamat ®, Zantac ®, Pepcid AC ®
Is it fair when a commercial compares the fast action of an antacid to an acid inhibitor that takes up to 7 days to build up?
Section 2.1—Types of Matter
Matter can be classified
Matter
Pure Substances
Mixtures
Element CompoundHomogeneous
(Solutions)Heterogeneous
Matter
• Anything that has mass and takes up space• Anything made from atoms• Examples:
– Molecules– Cells– People– Air– Water
Pure Substances versus Mixtures
MixturesPure Substances
Every piece of matter is the same
More than one type of matter mixed together
Matter is classified as either a pure substance or a mixture
Elements versus Compounds
CompoundElements
Every atom is the same type of atom
More than one type of atom chemically bonded together.
Every molecule is the same.
Pure substances are either elements or compounds
Elements
Pure substanceEvery atom is the same
Elements can be found on the periodic table!
Element
Single AtomCannot be separated by chemical or physical processes
Compounds
Pure substanceEvery molecule is the same
Compound
Single Molecule
Made of more than one type of atom bonded together
Can be separated by chemical reactions only
Mixtures
HeterogeneousHomogeneous (aka “solution”)
It looks the same throughout
Different matter can be seen (chunks, bubbles, floaties,
layers, etc.)
Mixtures can be classified as homogeneous or heterogeneous
Mixtures
Not a pure substancePhysical combination of more than 1 type of pure substance
Mixture
>1 different type of matter
Can be separated chemically or physically
Mixture possibilities
• Mixtures can be any combination of solids, liquids and gases:– Solid-solid: Medicine tablet– Solid-gas: Pop Rocks candy– Solid-liquid: Ice water– Liquid-liquid: Lemon water– Gas-Liquid: Carbonated water– Gas-Gas: Air
True solutions, Colloids & Suspensions
ColloidTrue Solution
Particles don’t settle out and are
too small to scatter light
Particles don’t settle out but are large enough to
scatter light
Suspension
Particles will settle out over time
Dissolved Particle Size Increases
Particles Scattering Light
• If the dissolved particles are large enough to scatter light, we say it exhibits the “Tyndall Effect”
SolutionLight passes through unchanged
Colloids exhibit the Tyndall EffectLight is scattered by larger solute particles
Connect these concepts with Antacids
• What type of matter do you think antacids are?– Pure substance (Element or compound)– Mixture (homogeneous or heterogeneous)
Let’s Practice
Tin foilExample:
Determine if each is element,
compound, homogeneous or heterogeneous
mixtures
Copper pipe
Concrete
Carbon tetrachloride
Sports drink
Section 2.2—Naming Chemicals
We need to be able to name the chemicals in the antacids!
Matter can be classified
Matter
Pure Substances
Mixtures
Element CompoundHomogeneous
(Solutions)Heterogeneous
Matter
• Anything that has mass and takes up space• Anything made from atoms• Examples:
– Molecules– Cells– People– Air– Water
Pure Substances versus Mixtures
MixturesPure Substances
Every piece of matter is the same
More than one type of matter mixed together
Matter is classified as either a pure substance or a mixture
Elements versus Compounds
CompoundElements
Every atom is the same type of atom
More than one type of atom chemically bonded together.
Every molecule is the same.
Pure substances are either elements or compounds
Elements
Pure substanceEvery atom is the same
Elements can be found on the periodic table!
Element
Single AtomCannot be separated by chemical or physical processes
Compounds
Pure substanceEvery molecule is the same
Compound
Single Molecule
Made of more than one type of atom bonded together
Can be separated by chemical reactions only
Mixtures
HeterogeneousHomogeneous (aka “solution”)
It looks the same throughout
Different matter can be seen (chunks, bubbles, floaties,
layers, etc.)
Mixtures can be classified as homogeneous or heterogeneous
Mixtures
Not a pure substancePhysical combination of more than 1 type of pure substance
Mixture
>1 different type of matter
Can be separated chemically or physically
Mixture possibilities
• Mixtures can be any combination of solids, liquids and gases:– Solid-solid: Medicine tablet– Solid-gas: Pop Rocks candy– Solid-liquid: Ice water– Liquid-liquid: Lemon water– Gas-Liquid: Carbonated water– Gas-Gas: Air
True solutions, Colloids & Suspensions
ColloidTrue Solution
Particles don’t settle out and are
too small to scatter light
Particles don’t settle out but are large enough to
scatter light
Suspension
Particles will settle out over time
Dissolved Particle Size Increases
Particles Scattering Light
• If the dissolved particles are large enough to scatter light, we say it exhibits the “Tyndall Effect”
SolutionLight passes through unchanged
Colloids exhibit the Tyndall EffectLight is scattered by larger solute particles
Connect these concepts with Antacids
• Inactive ingredients might– Add enough volume to make the pill able to be
handeled– Add color– Add flavor– Allow the tablet to be compressed and formed
Let’s Practice
Tin foilExample:
Determine if each is element,
compound, homogeneous or heterogeneous
mixtures
Copper pipe
Concrete
Carbon tetrachloride
Sports drink
Section 2.2—Naming Chemicals
We need to be able to name the chemicals in the antacids!
Binary Ionic compounds
Definitions
Binary Ionic Compound- compound containing two elements—one metal and one non-metal
+Cation
+Cation
-Anion
-Anion Ionic Compound
Ionic bond- bond formed by attraction between + and - ions
Metals & Non-MetalsIonic Bonds are between metals & non-metals
H He
Li Be B C N O F Ne
Na Mg Al Si P S Cl Ar
K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr
Rb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I Xe
Cs Ba Lu Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po At Rn
Fr Ra Lr Rf Db Sg Bh Hs Mt Uun Uuu Uub Uut
Metals Metalloids Non-metals
These compounds have:2 elements (“binary”)A metal & a non-metal (“ionic”)
To name these compounds:Write the name of the metal (the cation)Write the name of the non-metal (the anion) with
the suffix “-ide”
Identifying & Naming Binary Ionic
The subscripts in the formula do not matter when naming this type
Example #1
NaCl
Cation
Anion
“Sodium”
“Chlorine” becomes “Chloride”
Sodium Chloride
Example #2
Cation
Anion
“Calcium”
“Bromine” becomes “Bromide”
CaBr2
Calcium Bromide
Example #3
K2O
Cation
Anion
“Potassium”
“Oxygen” becomes “Oxide”
Potassium Oxide
Let’s Practice
Example:Write the name for the following
compounds
CaF2
Na3P
NaCl
SrBr2
Polyatomic Ionic Compounds
Definition
Polyatomic Ion- more than one atom that together have a charge
+Cation
+Cation
Polyatomic Ionic Compound- compound containing at least one polyatomic ion
-Polyatomic
Anion
Polyatomic IonicCompound
Common Polyatomic Ions
COMMON POLYATOMIC IONS
Acetate, CH3COO-1 or C2H3O2-1
Ammonium NH4+1
Bromate, BrO3-1
Bromite, BrO2-1
Carbonate, CO3-2
Carbonite, CO2-2
Chlorate, ClO3-1
Chlorite, ClO2-1
Chromate, CrO4-2
Cyanide, CN-1
Dichromate, Cr2O7-2
Dihydrogen phosphate, H2PO4-1
Hydrogen carbonate or bicarbonate, HCO3
-1
Hydrogen phosphate or biphosphate, HPO4
-2
Hydrogen sulfate or bisulfate, HSO4-1
Hydroxide, OH-1
Hypochlorite, ClO-1
Iodate, IO3-1
Iodite, IO2-1
Nitrate, NO3-1
Nitrite, NO2-1
Oxalate, C2O4-2
Perchlorate, ClO4-1
Permanganate, MnO4
-1
Peroxide, O2-2
Phosphate, PO4-3
Phosphite, PO3-3
Silicate, SiO3-1
Sulfate, SO4-2
Sulfite, SO3-2
The Appendix of your book (Page A-2) has the following chart
The only cation (front-half) polyatomic ion is “NH4”
All other polyatomic ions are anions (back-half)
The subscripts within the polyatomic ion is important (it must match exactly with the one on your ion list)
If there are parenthesis, the polyatomic ion is inside (ignore the number outside)
Help Identifying Polyatomic Ions
Practice Identifying Polyatomic Ions
Example:Identify and
name the polyatomic ion in each compound
NaNO3
NH4Cl
Ca(OH)2
(NH4)3PO4
K2CO3
These compounds have:More than 2 capital letters (non starting with H)Contain at least 1 metal & 1 non-metal
To name these compounds:Write the name of the cation (the metal element
name or “Ammonium” for “NH4”)If the anion is a polyatomic ion, write the polyatomic
ion’s name just as it isIf the anion is a single non-metal element, write its
name with the suffix “-ide”
Identifying & Naming Polyatomic Ionic
Example #4
NaNO3
Cation
PolyatomicAnion
“Sodium”
“Nitrate”
Sodium Nitrate
Example #5
Cation
PolyatomicAnion
“Potassium”
“sulfate”
K2SO4
Potassium sulfate
Example #6
Ca(OH)2
Cation
PolyatomicAnion
“Calcium”
“hydroxide”
Calcium hydroxide
Let’s Practice
Example:Write the name for the following
compounds
Ca(NO3)2
Na3PO4
NH4ClO
K2CO3
Multivalent Metals
Definition
Multivalent Metal- metal that has more than one possibility for cationic charge
The Appendix of your book (Page A-2) has the following chart
Common multivalent metals and their charges
Cobalt Co+2 Co+3
Copper Cu+1 Cu+2
Iron Fe+2 Fe+3
Lead Pb+2 Pb+4
Manganese Mn+2 Mn+3
Mercury Hg2+2 Hg+2
Tin Sn+2 Sn+4
These compounds have:One of the multi-valent metals in that chart
To name these compounds:Write the name of the metal element (cation)Write the name of the anion (element name with “-ide” or
polyatomic ion name)Determine the total negative chargeTotal negative charge = total positive charge for all neutral
compoundsDetermine the charge on each metal atomWrite the charge in roman numerals in parenthesis after the
metal’s name
Identifying & Naming Multivalent Metals
Common Ions
N3-
O2-
F-
P3-
S2-
Cl-
Se2-
Br-
I-
Periodic table--Charges of common ions
Use the periodic table to determine charges on common elemental anions
Example #8
CuCl
Cation
Anion
“Copper”
“Chlorine” becomes “Chloride”
Copper Chloride
Chloride has a –1 charge
-1 charge * 1 ion = -1
A –1 charge needs a +1 charge
Therefore, copper must be +1
(I)
Example #9
Fe2(CO3)3
Cation
Polyatomic Anion
“Iron”
“Carbonate”
Iron carbonate
Carbonate has a –2 charge
-2 charge * 3 ions = -6
A –6 charge needs a +6 charge and there are 2 iron ions
Therefore, iron must be +3
(III)
Let’s Practice
Example:Write the name for the following
compounds
PbCl2
PbCl4
MnO
Mn2O3
Binary Covalent Compounds
Definition
Binary Covalent Compound compound made from two non-metals that share electrons
NonmetalNon
metalNon
metalNon
metal Covalent compound
Covalent bond atoms share electrons
These compounds have:2 elements (“binary”)Both non-metals (“covalent”)
To name these compounds:Write the name of the first element with the prefix
indicating the number of atoms (except don’t use “mono-”)
Write the name of the second element with the prefix indicating the number of atoms (including “mono-”) and the suffix “ide”
Identifying & Naming Binary Covalent
Covalent PrefixesThe Appendix of your book (Page A-2) has the following chart
PREFIXES USED IN MOLECULAR COMPOUNDS1. mono-
2. di-3. tri-
4. tetra-5. penta-6. hexa-7. hepta-8. octa-9. nona-10.deca-
Example #10
P2O5
Phosphorus
Oxygen
2 = “di-”
5 = “penta-”Use “-ide”
Diphosphorus pentaoxide
Example #11
Silicon
Oxygen
Don’t use “mono-” on first element
2 = “di-”Use “-ide”
SiO2
Silicon dioxide
Let’s Practice
Example:Write the name for the following
compounds
CO2
N2O4
P4O10
CO
Nomenclature Summary
Naming Chemical Formulas
Starts with a metal or NH4
Does not contain a metal = Binary
Covalent compound
2 capital letters = Binary Ionic
More than 2 elements = Polyatomic Ionic
Mixed Practice
Example:Write the name for the following
compounds
Na2O
K3PO4
Cu(OH)2
(NH4)2S
MgCl2
Section 2.3—Chemical Formulas
We need to be able to read the formulas for chemicals in the antacids!
Your Appendix (Page A-2) has lists of:Common polyatomic ionsMultivalent metalsCovalent prefixes
Use your periodic table to determine the charges of common elements when they form ions
Reminders from Section 2.2
Binary Ionic compounds
Definitions
Binary Ionic Compound- compound containing two elements—one metal and one non-metal
+Cation
+Cation
-Anion
-Anion Ionic Compound
Ionic bond- bond formed by attraction between + and - ions
Metals & Non-MetalsIonic Bonds are between metals & non-metals
H He
Li Be B C N O F Ne
Na Mg Al Si P S Cl Ar
K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr
Rb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I Xe
Cs Ba Lu Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po At Rn
Fr Ra Lr Rf Db Sg Bh Hs Mt Uun Uuu Uub Uut
Metals Metalloids Non-metals
Example #1
Sodium chloride
Cation
Anion
Na+1
Cl-1
NaCl
Na+1Cl-1
+1 + -1 = 0
The compound is neutral…no subscripts are needed.
Example #2
Calcium bromide
Cation
Anion
Ca+2
Br-1
CaBr2
Ca+2Br-1
+2 + -1 = +1
Ca+2Br-1Br-1
The subscript “2” is used to show that 2 anions are needed.
+2 + -1 + -1 = 0
Let’s Practice
Example:Write the following chemical formulas
Cesium chloride
Potassium oxide
Calcium sulfide
Lithium nitride
Polyatomic Ionic Compounds
Definition
Polyatomic Ion- more than one atom that together have a charge
+Cation
+Cation
Polyatomic Ionic Compound- compound containing at least one polyatomic ion
-Polyatomic
Anion
Polyatomic IonicCompound
These compounds:Do not end with “-ide” (except hydroxide & cyanide)Do not use covalent prefixes
To write these formulas:Write the symbol & charge of the cation & anionAdd additional cations or anions to have a neutral compoundUse subscripts to show the number of ions
When using subscripts with a polyatomic ion, you must put the polyatomic ion in parenthesis.
Identifying & Naming Polyatomic Ionic
Example #3
Sodium carbonate
Cation
PolyatomicAnion
Na+1
CO3-2
Na2CO3
Na+CO32-
+1 + -2 = -1
Na+Na+CO32-
The subscript “2” is used to show that 2 cations are needed.
+1 + 1 + -2 = 0
Example #4
Magnesium nitrate
Cation
PolyatomicAnion
Mg+2
NO3-1
Mg(NO3)2 Use parenthesis when adding subscripts to polyatomic ions
Mg+2NO3-
+2 + -1 = 1
Mg+2NO3- NO3
-
The subscript “2” is used to show that 2 anions are needed.
+2 + -1 + -1 = 0
Let’s Practice
Example:Write the following chemical formulas
Sodium nitrate
Calcium chlorate
Potassium sulfite
Calcium hydroxide
Multivalent Metals
Definition
Multivalent Metal- metal that has more than one possibility for cationic charge
These compounds:Will have roman numerals
To write these formulas:Same as binary ionic or polyatomic ionic.The roman numerals tell the charge of the metal
(cation)
Identifying & Naming Multivalent Metals
Example #5
Iron (III) oxide
Cation
Anion
Fe+3
O-2
Fe2O3
Fe+3O2-
+3 + -2 = -1
Fe+3Fe+3O2-O2-
The subscript “2” and “3” are used to show the numbers of atoms needed.
+3 + 3 + -2 + -2 + -2 = 0
Example #6
Copper (II) nitrate
Cation
PolyatomicAnion
Cu+2
NO3-1
Cu(NO3)2
Cu+2NO3-
+2 + -1 = 1
Cu+2NO3-NO3
-
Use parenthesis when adding subscripts to a polyatomic ion
+2 + -1 + -1 = 0
Let’s Practice
Example:Write the following chemical formulas
Iron (II) nitrate
Copper (I) chloride
Lead (IV) hydroxide
Tin (II) oxide
Let’s Practice
Example:Write the following chemical formulas
Iron (II) nitrate
Copper (I) chloride
Lead (IV) hydroxide
Tin (II) oxide
Binary Covalent Compounds
Definition
Binary Covalent Compound compound made from two non-metals that share electrons
NonmetalNon
metalNon
metalNon
metal Covalent compound
Covalent bond atoms share electrons
These compounds:Use covalent prefixes
To write these formulas:Write the symbols of the first and second elementUse the covalent prefixes (assume the first element
is “1” if there’s no prefix) as the subscripts to show number of atoms.
Identifying & Naming Binary Covalent
Atoms do not form charges when bonding covalently…you DO NOT need to worry about charges with this type!
Example #7
Dinitrogen Tetraoxide
N
O
“Di-” = 2
“Tetra-” = 4
N2O4
Example #8
Silicon dioxide
Si
O
“Mono-” is not written for the first element
“Di-” = 2
SiO2
CAUTION!!!
bi-di-
Stands for “2” in covalent compounds
Means there’s a hydrogen in the polyatomic anion
“di” and “bi” do not mean the same thing!
Carbon dioxide = CO2 Sodium biphosphate = Na2HPO4
Let’s Practice
Example:Write the following chemical formulas
Carbon monoxide
Nitrogen dioxide
Diphosphorus pentaoxide
Nomenclature Summary
Writing Chemical Formulas
Does not contain covalent prefixes
Does contain covalent prefixes = Binary
Covalent compound
Ends with “-ide” (except hydroxide &
cyanide) = Binary Ionic
All others = Polyatomic Ionic
Mixed Practice
Example:Write the following chemical formulas
Magnesium hydroxide
Copper (II) nitrate
Iron (III) oxide
Nitrogen dioxide
Sodium bicarbonate
Section 2.4—Defining, Naming & Writing Acids & Bases
We need to know what acids behave when talking about ant-acids!
Acids
Acids – Arrhenius Definition
• Produce Hydronium ion (H3O+1) in water• Hydronium ion is water + a hydrogen cation
H
OH
water
H+1
H
OH
H +1
By this definition, if an acid is to give a H+1 to water, then all acids will have hydrogen as the cation (first element written).
How do Acids produce Hydronium?
H
OH
H -
water acid
Hydrogen cation with some anion
How do Acids produce Hydronium?
H
OH
H -+1
How do Acids produce Hydronium?
H
OH
H+1 -
Hydronium ion Anion
Naming Acids
These compounds have:Start with “H” (more than 1 “H” is OK, too).Do not contain oxygen
To name these compounds:Use “hydro____ic acid”Fill in the blank with the anion’s name without the
last syllable
Naming non-oxygen Acids
Example #1
HBr
Hydrogen cation
Bromine
It’s an acid
No oxygenUse “hydro___ic”
Hydrobromic acid
These compounds have:Start with “H” (more than 1 “H” is OK, too).Do contain oxygen
To name these compounds:Use “___ic acids” for “-ate” anionsUse “___ous acids” for “-ite” anions
Naming Oxygen Acids
Do not use “hydro” with these…the word “acid” is how you know it begins with hydrogen, not “hydro-”
Example #2
Hydrogen cation
Sulfite ion
It’s an acid
“-ite” ionUse “___ous” acid
H2SO3
Sulfurous acid
Example #3
Hydrogen cation
Sulfate ion
It’s an acid
“-ate” ionUse “___ic”
H2SO4
Sulfuric acid
Let’s Practice
Example:Write the name for the following
compounds
HCl
HNO3
H2S
H3PO3
Writing Acid Formulas
To write these formulas:The cation is H+1
Write the anion and chargeBalance the charges by adding the appropriate
subscript to the hydrogen cation
“Hydro-” acids
Example #4
Hydrofluoric acid
Hydrogen cation
Does not contain oxygen
H+1
F-1
HF
H+1F-1
+1 + -1 = 0
The compound is neutral.Subscripts are not needed
To write these formulas:The cation is H+1
If it is an “-ic” acid, the anion is the “-ate” polyatomic ion
If it is an “-ous” acid, the anion is the “-ite” polyatomic ion
Add subscript to the hydrogen cation to balance charges
NON “Hydro-” acids
Example #5
Carbonic acid
Hydrogen cation
From the “___ate” anion
H+1
CO3-2
H2CO3
H+CO32-
+1 + -2 = -1
H+H+CO32-
+1 + 1 + -2 = 0
Example #6
Nitrous acid
Hydrogen cation
From the “___ite” anion
H+1
NO3-1
HNO2
H+NO2-
+1 + -1 = 0
Let’s Practice
Example:Write the
formula for the following acids
Phosphoric acid
Hydroiodic acid
Carbonous acid
Perchloric acid
Bases
Bases – Arrhenius Definition
• Bases produce the hydroxide ion in water
HO-1
Hydroxide Ion
Naming & Writing Bases
Most bases are just ionic compounds with “hydroxide” as their anion
The most common exception to this is ammoniaNH3 (ammonia) is a base even though it doesn’t
contain “-OH” as the anion
Naming Bases
Example #7
NaOH
Sodium
Hydroxide
Sodium Hydroxide
Let’s Practice
Example:Write the
formula or name for each
Ca(OH)2
KOH
Sr(OH)2
Copper (II) hydroxide
Magnesium hydroxide
Section 2.5—Characteristics of Acids and Bases
Now that we know what acids are, how do they act?
Characteristics of Acids & Bases
BasesAcids
Produce H3O+1 (hydronium ion) in water
Produce OH-1 (hydroxide ion) in water
Tastes sour Tastes Bitter
React with active metals to form hydrogen gas Feels slippery
Strength versus Concentration
Review of how acids produce ions
H
OH
H+1 -
Hydronium ion Anion
Strong versus Weak Acids
+
++
-
-
-
Strong acidMost of the acid molecules
have donated the H+1 to water
How many hydronium ion – anion pairs can you find?
How many intact acid molecules can you find?
3
1
Strong versus Weak Acids
+
-
Weak acidOnly a few of the acid
molecules have donated the H+1 to water
How many hydronium ion – anion pairs can you find?
How many intact acid molecules can you find?
1
3
Concentrated versus Dilute
solute solvent
Lower concentration
Not as many solute (what’s being dissolved) particles
Higher concentration
More solute (what’s being dissolved) particles
Combinations of Concentration & Strength
DiluteConcentrated
A lot of acid added & most
dissociates
Not much acid added, but most of
what’s there dissociates
A lot of acid added, but most
stays together
Not much acid added and most of what is there stays
together
Strong
Weak
All of the same ideas apply to bases as well (concentration and strength)
Many people think all acids are dangerous and all bases are more safeVinegar is an acid we eat…some of them are safe!Sodium hydroxide is a very caustic base…not all of
them are less harmful than acids!The stronger and acid or base is (and the more
concentrated it is), the more dangerous it is for you
Other notes
pH
Is a scale to measure the acidity of a sample
pH Scale
1 14
Highly acidic Very basic (not acidic)
neutral
7
Chapter 6 will give more detail about how pH is calculated!
Indicators change color based on pHLiquid indicators – various indicators change colors at different
pH’sUniversal indicator – a combination of liquid indicators to
produce a “rainbow” changing colors at several pH’sPaper Indicators
Paper with a liquid indicator on it (Litmus paper or pH paper)pH meters or pH probes
Electronically determine pH and give a read-out
Ways to measure pH
Common pH indicators
This picture © 1998 David Dice
pH of common substances
SUBSTANCE PH
0.1M HCl 1
Stomach contents
2
Vinegar 2.9
Soda pop 3
Grapes 4
Beer 4.5
Pumpkin pulp 5
Bread 5.5
Intestinal contents
6.5
Milk 6.5
Urine 6.6
Bile 6.9
Saliva 7
Blood 7.4
Eggs 7.8
0.1M NH3 (aq) 11.1
0.1M NaOH 13
Section 2.6—Chemical Reactions
If we’re going to do chemical reactions with antacids, we’d better know how to write them!
OO OO
Bonds and atoms are rearranged to form new compounds.
HH HH
OOHH
HHOOHH
HH HH HHThe compounds in the end are different from those in the beginning
Bonds are broken and formed between different atoms
2 H2 + O2 2 H2O
Chemical Reactions
Chemical Equations
The “sentence” of chemistry that shows how the starting materials and the final products of a chemical reaction
Examples of Chemical Equations
H Cl
HMg H
H Cl
Mg ClCl
H Cl
HMg H
H Cl
Mg ClCl
Word equation: magnesium metal is reacted with aqueous hydrochloric acid to produce aqueous magnesium chloride
and hydrogen gas
Visualization
Formula equation: Mg (s) + 2 HCl (aq) MgCl2 (aq) + H2 (g)
Parts of a Chemical Equation
NaCl (aq) + AgNO3 (aq) AgCl(s) + NaNO3 (aq)
Reactants
States of matter Arrow
Products
The starting materials for the reaction—each compound is separated by a “+”
s = solidl = liquidg = gasaq = aqueous (dissolved in water)
Read as:YieldsProducesFormsMakesetc.
Formed in the reaction
You must write each chemical formula correctly first! (Section 2.2)
“and”, “is mixed with” or “reacts with” = +“yield”, “produces” and “forms” =
Writing Chemical Equations
We will learn to balance equations in the next section, so don’t worry about it now!
Aluminum metal is reacted with hydrochloric acid to form aluminum chloride and hydrogen gas
Let’s Practice #1
Al + HCl AlCl3 + H2
Example:Write the word equation into symbol form
Copper (II) nitrate and sodium hydroxide form copper (II) hydroxide and sodium nitrate
Let’s Practice #2
Cu(NO3)2 + NaOH Cu(OH)2 + NaNO3
Example:Write the word equation into symbol form
NaCl + AgNO3 AgCl + NaNO3
Double Replacement ReactionsThe cations from two compounds replace each other.
ClClN
aNa
AgAg
OO OONN
OO
ClCl
AgAg
NaNa
OO OONN
OO
Two ionic compounds switch ions
Double Replacement Reactions
A X B Z A XBZAA XX BB ZZ AA XXBBZZ
General format of a double replacement reaction:
& balance charges with subscripts when writing formulasRemember to write cations first …
AgCl
CaCl2 + AgNO3
3
Ca(NO3)2 +CaCl2 AgNO3+
Products of a Double Replacement
Only leave subscripts that are in the original compound there if they are a part of a polyatomic ion!
Neutralization Reactions
General format of a neutralization reaction:
X B XBH HO HO
HXX BB XXBBH HOO HO
HH
OOH
Neutralization reactions are double replacement reactions where one cation is “H” and one anion is “OH” and water is formed
& balance charges with subscripts when writing formulasRemember to write cations first …
HOH
H2 SO4 + NaOH
3
Na2SO4 +H2 SO4 NaOH+
Products of a Neutralization Reaction
Only leave subscripts that are in the original compound there if they are a part of a polyatomic ion!
You can write the water as “HOH” when you combine the cation & anion or you can change it to “H2O”
Let’s Practice #3
SrBr2 + HOH
Example:Write the
products for this reaction
Sr(OH)2 + HBr
Let’s Practice #4
CaCl2 + HOH
Example:Write the
products for this reaction
HCl + Ca(OH)2
Section 2.7—Balancing Equations
We need to finish writing those equations we started!
Law of Conservation of Matter/Mass
Law of Conservation of Matter – Matter cannot be created nor destroyed during chemical or physical changes
Also called the Law of Conservation of Mass (since all matter has mass)
How Does the Law Lead to Balancing?
Law of Conservation
of MatterTherefore… So we must…
Matter cannot be created nor destroyed during a chemical or physical change
The matter on the reactants side and the matter one the products side must be the same
Ensure the numbers of each type of atom are the same on both sides of the equation…by balancing!
How do we Balance Equations?
2 H2 + O2 2 H2O
Subscripts
Coefficients
# of atoms in a compound
Number of compounds in the reaction
Subscripts balance charges within a compound.
Coefficients balance atoms in an equation
What do Coefficients Really Mean?
CH4 + 2 O2 CO2 + 2 H2O
Total:1 C4 H4 O
Total:1 C4 H4 O
The equation is balanced.
H
C
H
HH
O O
O O
CO O HO
H
HO
H
H
CC
H
HH
O O
O O
CCO O HO
H
HO
H
How to Balance Chemical Equations
4
Filling each coefficient location lets you and the grader know that you finished the problem rather than you left some blank because you weren’t done!
Place a “1” in any empty coefficient location
_____ __________2
How to Balance By Inspection:
Reactants Products
H
O
4
2 3
2
C 1 1
2
4
44
1 1CH4 + O2 _____ H2 O CO2+
Choosing the Order of Balancing
Save for laterElements that are uncombined
Save for laterElements that appear more than 1 time per side
StartElements that appear
only 1 time per side
StartElements in most
complicated molecules
How do you know what order to balance in?
Pb + PbO2 + H+ Pb2+ + H2O
To balance this equation, use the order: O, H, Pb
2
_____
What about a different order?How is it different if we balance in a different order?
Reactants Products
O
Pb
2
2 1
1
H 1
2
2
_____ __________1 21 2Pb Pb+ O2 H2 O Pb2++H+_____2+
2 4
4
4
You’ll still get to the correct answer, but it will take longer and be more complicated!
H, O, Pb
Polyatomic Ions
Polyatomic ion – Group of atoms that together has a net charge
e.g. Nitrate NO31-
Carbonate CO32-
5 Place a “1” in any empty coefficient location
__________ __________2
Balancing with Polyatomic Ions:
Reactants Products
PO4
Ca
1
1 3
2
H 3 1
1
6
3
3 6Ca (OH)2+H3 Ca3 (PO4)2 H2O+PO4
OH 2 1
HOH
6
2
6 6
Let’s Practice #1
Example:Balance the
following equation
__ HCl + __ Ca(OH)2 __ CaCl2 + __ H2O2 1 1 2
HOH
Did you see the “OH” polyatomic ion & change H2O to HOH?
Let’s Practice #2
Example:Balance the
following equation
__ H2 + __ O2 __ H2O2 1 2
Let’s Practice #3
Example:Balance the
following equation
__ Fe + __ O2 ___ Fe2O34 3 2
Section 2.8—Speeding Up A Reaction
How can we make those antacid reactions occur faster?
Kinetics & Reaction Rates
Kinetics – Study of the rates of reactions
Reaction Rate – Rate at which reactants produce products
Collision Theory
Collision Theory – Defines 3 circumstances to be met for a reaction to occur.
Reactants must collide
Collision must be at the correct orientation
Collision must have minimum energy for reaction to occur
1
2
3
Only a small number of collisions meet the requirements and result in a reaction
Collisions Must Occur
In order for two molecules to react, they must come in contact with one another
FF
FFNN
OO
OO
There’s no way they’ll ever react if they don’t run into one another!
NNOO
OO
FF
FF
Collision with Correct Orientation
For a collision to result in a chemical reaction, it must occur with the correct orientation
FF FF NNOO
OO
This is the correct orientation. The reaction will happen.
FF
FF
This collision had more energy (faster moving molecules). A reaction will occur..
NNOO
OO
Collision with Enough Energy
For a collision to result in a chemical reaction, it must occur with the minimum energy for reaction
FF FF NNOO
OO
Activation Energy
Minimum energy for reaction to occur during a collision
Reaction Coordinate Diagram
Products
Activated complex(Also called the transition state)
Activation Energy
ReactantsEnergy change for reaction
Reaction coordinate diagrams show the energy changes throughout the reaction
Reaction proceeds
Ene
rgy
F + FNO2
FF
FF
Activated Complex
What is an “activated complex”?
Reaction proceeds
Ene
rgy
NNOO
OOFF FF NN
OO
OO
ReactantsActivated Complex
Products
F2 + NO2
F2NO2
Factors Affecting Reaction Rates
Surface Area of ReactantsHow does the surface area of the reactants affect the reaction rate?
Reactants must collide in order to react
Larger surface area means more particles can come in contact with each other at the same time
More reactants can collide at the same time and a fraction of those will result in reaction
As surface area increases, reaction rate increases
Concentrations of ReactantsHow does the concentration of reactants affect the reaction rate?
Only a small fraction of the collisions meet the requirements and result in a reaction
More reactants mean more collisions will occur
If more collisions occur, more will meet the requirements and result in a reaction
As reaction concentration increases, reaction rate increases
Temperature
How does temperature affect the reaction rate?
Reactants must collide with at least energy equal to the activation energy
If molecules are at a higher temperature, they have a higher average kinetic energy
With higher energy molecules, collisions will have higher energy and more often result in reaction
For most reactions, as temperature increases, reaction rate increases
Catalysts
Catalysts – Substance that increases the rate of reaction without being used up
A + B + C D + C
“C” is the catalyst…it is present in the beginning and in the end
Enzymes are catalysts in the body
Catalysts
How do catalysts help speed up the reaction without being used?
They increase the chances that a collision will successfully produce a reaction
For example, catalysts hold one or more of the reactants in place to allow collisions to occur with the correct orientation
Once the reaction has occurred, the catalyst releases the molecule(s) and finds another one to help
Catalysts & Reaction DiagramsReaction Path without catalyst
Reaction Path with catalyst
Reaction proceeds
Ene
rgy
Catalysts lower the activation energy of the reaction by letting it proceed in a different way.
With lower activation energy, a higher percentage of collisions will be successful (they don’t need to collide with as much energy to be successful)
What did you learn about antacids?
Antacids
MixtureMixture
Are a
CompoundsCompounds
ChemicalFormulas
ChemicalFormulas
Collision Theory
Collision Theory
Acids & BasesAcids & Bases
Chemical ReactionsChemical Reactions
Of differentSymbolizedwith
Some are
Balanced Chemical Equations
Balanced Chemical Equations
undergo
Symbolizedwith
Used in
Speed governed by