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Chemistry 12 Final Project
Transcript of Chemistry 12 Final Project
amount of product formed OR amount of reactant used
time interval time interval amount to sum it up... time symbolizes
"change in" How To Measure A Reaction Rate: To figure out the rate of a reaction you can also look at the physical changes that occur for example:
Color Changes - rate= color intensity/ time
Temperature Changes - rate= temperature/ time
Mass Changes - rate= mass/ time
Concentration Changes - rate= solution/ time
Pressure Changes - rate= pressure/ time ...it is the speed of a reaction also known as the "rate of reaction" What determines the outcome of a reaction rate?
The rate will be dependent on the nature of the reactants and the conditions needed for the reaction to take place. The following factors affect how a reaction occurs: 1) Temperature - if it decreases the kinetic energy (KE) slows down, giving us a slower reaction rate. If it increases the kinetic energy speeds up, causing the reaction rate to double. 2) Concentration Of The Reactants - when the concentration of reactants is increased the speed of both the homogeneous and heterogeneous reactions is increased because there is more of the solution to react with. If you decrease the concentration the rate decreases, giving us a lower chance of a reaction to take place. Homogeneous Reaction: When all the reactants present are in the same phase. Usually these are faster reactions because the molecules reacting have a better colliding capability. The possibilities are all faster moving molecules, for example a reaction with two gases, or two liquids, or two aqueous (dissolved in water) reactants. Two solid reactants do not react as a homogeneous reaction. Heterogeneous Reaction: When all the reactants present are in different phases. Usually these are slower reactions because it takes a larger surface area to get a reaction. There are many more possibilities when considering a heterogeneous reaction, for example a reaction with a solid and a liquid, a liquid and a gas, or a solid and a gas. The only exception to this is that two solid reactants qualify as a heterogeneous reaction. 5) Phases In A Reaction:
solids: slowest to react since there is very little movement, usually the particles just vibrate against each other
liquids: react faster then solids because there is more room to move for the particles
gases: react fast since the particles of a gas substance are already moving fast
aqueous ions: are the fastest reacting particles because of how close they are to each other so it is easy to move around solutions. They also attract a strong charge.
simply said from slowest to fastest...
solids - liquids - gas - aqueous The "Hot Tamale" candies are homogeneous because they are all the same candy mixing with each other. The "Skittles" are heterogeneous because there are more then one flavor or color of candy mixed together. 3) Pressure - this affects the reaction rate the same way concentration does, except this applies to gases only! 4) The Nature Of Reactants - some reactions happen quicker or slower than others because the bonds involved in there make up have different strengths. Stronger bonds = slower reaction, weaker bonds = faster reaction. 6) Surface Area - the larger the area there is to react, the faster the reaction rate will take place. The reactants have a better chance of meeting each other if there is a larger surface area. 7) Catalyst - something added to a chemical reaction that does not get used up or affect the reaction itself, it just speeds up the reaction rate.
Inhibitor - has the opposite affect of a catalyst, where instead of speeding up, it slows down the reaction rate. = Ea (f) Activation Energy in the Forward Reaction
Activation Energy (Ea): the least amount of energy required for a molecule to be able to react, in an endothermic reaction. The activation energy uses the least amount of potential energy (PE) to turn the reactants into the activated complex. If there is not enough energy, no product will form in the reverse of forward direction. The lower the activation energy is or "the smaller the hill is" the faster a reaction rate will be. On a diagram it is said to be what is needed to get over the hill to reach the peak. HIGH Ea=SLOW RATE & LOW Ea=FAST RATE -Rate Determining Step: the slowest step in the overall reaction, which determines the rate. Collision Theory: can be defined as molecules that have the ability to bounce off each other. The bouncing of molecules is a chemical reaction.
for a chemical change to occur two things must be present... Sufficient Energy and Correct Structure (Geometry) We already know that if you have a high concentration the reaction rate will increase. Now we can build upon this to say, if the reaction rate is increased it means we have more collisions taking place. Which of the following units can be used to express the rate of a chemical reaction?
A) ml/g B) mol/L C) g/mol D) mol/min D! Correct! the higher the concentration, the more collisions per second we have. therefore... Kinetic Energy (KE):
the increase in temperature automatically increases the kinetic energy (KE) of molecules giving us a greater reaction rate. The more KE present, the faster the molecules move, and the number of collisions occurring with a greater energy increases. **Temperature is the only factor which affects kinetic energy. Enthalpy (Heat Energy):
the energy or heat aspect of a reaction is called "enthalpy" usually expressed in kJ. The change in heat is shown by H. The two types of change are:
H - combined enthalpies of all reactants
H - combined enthalpies of all products products reactants Endothermic Reaction: Exothermic Reaction: absorbs energy and the products have more energy than the reactants releases energy and the products have less energy than reactants I love ABSORBING
the heat during
these cold winter
months! How to show an endothermic reaction on a potential energy diagram. How to show an exothermic reaction
on a potential energy diagram. [Activation Energies] Activated Complex: the point where kinetic energy (KE) turns into potential energy (PE) to form a not long lasting, unbalanced, molecule with a high energy. At this point the molecules are reorganizing themselves to go from reactants to products. The activated complex is known as the peak or top of the hill on this potential energy diagram. = E Energy Of Reactants
The energy of reactants in a reaction. The reactants are gaining potential energy (PE) by slowing down as they approach one another. react = Ea (r) Activation Energy in the Reverse Reaction
Since reactions can go in both the forward and reverse direction the same rules apply to the reverse direction as they do to the forward. = H
The change in heat energy is measured at this point of the diagram. = E Energy Of Products
The energy of products in a reaction. The products are losing potential energy (PE) by speeding up and turning the PE into KE. prod = Energy Of Activated Complex
The total energy needed to reach the activation complex. What is equilibrium?
Double arrows in a chemical reaction means it is a reversible reaction which is when products can react to form reactants and vice versa. This occurs when two reactions are against each other. Products are made and reactants reform, all in a simultaneous closed system. The rate in for forward direction as it is in the reverse, so reactants are formed just as fast as products.
Solubility is defined as the concentration of a substance in solution at a specific temperature when it is at equilibrium.
Electrolyte is a substance that dissolves to give a solution that has electrically conducting ions. The more ions you have, the higher electrical conductivity.
Non-Electrolyte is a substance that dissolves to give a non-electrical conducting solution that has only molecules. Key Terms: As a result you get either a molecular solution with neutral molecules or an ionic solution that has only ions. The more ions in solution you have, the higher the electrical conductivity. How can you tell if a solution is molecular or ionic? 1) a metal and non-metal compound = ionic
2) a compound made of polyatomic ions = ionic
3) a non-metal and non-metal compound/
organic compound = molecular solution Saturated Solution: a solution that has dissolved the maximum amount of a substance, but it must also meet 2 circumstances:
1) it must contain some undissolved material
2) equilibrium must exist between the dissolved and undissolved material. When a solid is dissolving into a solution the dissolving reaction is always equal to the rate of crystallization of the solid. What is the difference between equilibrium & dynamic equilbrium?
Equilibrium: A reversible reaction that has an equal forward and reverse reaction rate that has a closed system so no products or reactants are lost.
Dynamic Equilibrium: When microscopic or small changes occur at equilibrium. How do you know a reaction has reached equilibrium?
You know equilibrium has been reached when a constant property of color, concentration and pressure change are present.
** equilibrium can only be reached in a CLOSED system, so nothing goes in or out What affects equilibrium?
1) Temperature --> a new equilibrium is
always established at a new temperature
2) It does not matter whether you start
with an excess of products or reactants
because it will eventually reach
3) no MACROscopic or noticeable changes
occur during equilibrium Characteristics Of Equilibrium:
b) reverse reaction occurs at same rate
c) equilibrium is reached by beginning with either reactants or products
d) temperature is constant
The forward and reverse reaction still continue even when equilibrium is reached, which is why equilibrium is called dynamic.
a) forward rate = reverse rate
b) concentration of reactants and products is different
c) concentration of reactants and products stays constant but do not equal each other Enthalpy H: the energy component of a reaction.
A reaction will tend to move to the side with the lowest activation energy because we always want to use minimum energy (minimum enthalpy). This is sometimes known as the "laziness." We want to get over the smallest hill, since that is the least amount of energy needed. Entropy S: the amount of randomness in a system as time goes on. Always want maximum entropy.
Levels Of Randomness
a) solids - very orderly
b) pure liquids - a lot more random than solids
c) solutions - more random than pure liquids because mixtures being more mixed around
d) gases a lot more random than solutions Spontaneous Change: a change that happens by itself and without any help. - enthalpy and entropy are opposite each other = equilibrium
- enthalpy and entropy favor products = 100% completed
- enthalpy and entropy favor reactants = 0% completed REMEMBER catalysts have no impact. It does though allow equilibrium to be reached quicker. Le Chatelier's Principle: Closed system at equilibrium is about to change, it will try to reverse that change. Effect Of Temperature Change:
decrease heat energy, the reaction will shift meaning it has to produce more heat and vice versa
Example: N O 2NO
At time "t" the temperature was changed. Effect Of Concentration Change:
if concentration is increased, reaction shifts decreasing the amount of what was added
Example: 2HI H + I
At time "t1" HI was added. Effect Of Pressure Change:
decrease in volume will increase the pressure, increasing the concentration of any gas
Example: I + Cl 2ICl + energy
-to shift towards the side containing the fewest moles of gas, you must increase the pressure
-adding inert gas has no effect 2 4 (g) --> <-- 2 (g) <-- --> 2(g) 2(g) 2(g) 2(g) --> <-- (g) Keq & The Equilibrium Constant:
-A constant ratio of [reactants] to [products] is called a equilibrium constant which is shown as "Keq".
-Solids in equilibrium are kicked out of town and thrown against a fire hydrant because of constant density. ONLY gases, aqueous and 2 liquids are aloud in this house.
**REMEMBER FOR LIQUIDS THERE MUST BE TWO! NOT JUST ONE ALONE!** The Chemistree! What is a reaction rate? A! Correct! D! Correct! A! Correct! A! Correct! I RELEASE energy
when the contents
inside me gets mixed together to provide relief to athletes everywhere! Reaction Mechanism: This diagram is a visual representation of a reaction mechanism and shows the steps with individual activated complexes and activation energies. Potential Energy Diagram Of A Reaction Mechanism: Catalyst: lowers the energy needed to get over the "hill" to speed up a reaction, but does not get used up in the overall reaction. [The Affect Of A Catalyst On Activation Energy:] -Catalyst: is added as a reactant in a and does play a key role in the reaction. It gets used to lower activation energy, and shows up as a product in another step, leaving us with just as much catalyst as we initially started with. The written formula expression for a reaction mechanism looks like this: Reaction Mechanism: a step by step sequence that makes up a chemical reaction because most reactions are to complex to happen in just a single step. -Reaction Intermediate: can exist on its own and gets formed in one step then used up in another, but doesn't show up in the final reaction. Catalyst in the above reaction is "I". Reaction Intermediate in the above
reaction is "IO". Rate Determining Step in the above reaction is the first step. B! Correct! B! Correct! B! Correct! D! Correct! D! Correct! 2NO N + O The equilibrium: --> <-- (g) 2 2 Keq = [N ][O ]
[HI][HI] Since there is a coefficient in the equilibrium, we always put the coefficient as an exponent: Keq = [N ][O ]
[HI] Has a Keq: 2 2 2 2 2 so far we know...
-changing the concentration or pressure of a gas does not affect the Keq
-changing the temperature DOES change the Keq since the KE of particles are changed, temperature is the ONLY change that affects Keq value
-increasing temperature - increases [reactants] & decreases [products], results in Keq decreasing
-decreasing temperature - increases [products] & decreases [reactants], results in Keq increasing
ex. 2NO + O 2NO + 59kJ
...if we decrease temperature the equilibrium shifts right to make more where it was lost, so the products are favored and the Keq will be bigger
**if Keq is large products are favored
**if Keq is small reactants are favored 2 2 --> <-- 2 Calculations: There are 3 things you will be asked to calculate:
2) Equilibrium Concentrations of products, reactants, or both
3) Initial Concentrations of products, reactants, or both Initial Concentration: B! Correct! Electrochemistry is the change from chemical energy to electrical energy. Batteries is a phenomenal example of this.
For this to happen, electrons must move from one reactant to another.
Example: Zn + Cu+2 --> Cu + Zn+2
the electron moves from Zn to the Cu+2
...we can set up this reaction experimentally to produce electricity Electrochemical Cell a.k.a Battery:
Electrochemical Cell - a system that produces electrical energy
...we can show the reaction from above through a electrochemical cell Electrons flow from the zinc strip to the copper strip. Zn + Cu +2 ------> Cu + Zn +2
This involves the loss and gain of their electrons in the reaction occurring. Half of this is called a half cell or when split up, a half reaction.
Zn --> Zn+2 +2e- and Cu+2 + 2e- --> Cu
LOSING GAINING Salt Bridge: contains an electrolyte solution that does not get in the way of the cells job. It keeps everything neutral. Reactions that go through a lose and gain of electrons are known as redox or reduction-oxidation reactions.
ex. Pb + Au --> Pb + Au
...we can break this redox reaction into its half-reactions to find which is the oxidation and which is the reduction Solutions remain neutral because of ions moving back and forth. If this bridge is removed the reaction will come to a stop. It will also stop if the flow of electrons does not happen. electrolyte solution a.k.a gatorade Oxidizing Agent: whatever the reduction is
...in the last example we saw that the reduction of this reaction:
Pb+2 + Au(s) --> Pb(s) + Au+3
the half reaction was..
Pb+2 + 2e- --> Pb(s)
the oxidizing agent of this reduction reaction is opposite this! so Au(s) is the oxidizing agent which causes Pb+2 to reduce Reduction Reaction: half reaction where they gain electrons, more (-) charged
Pb + 2e --> Pb
...we see that the Pb charge went from +2 to 0 Oxidation Reaction: half reaction where they lose electrons, more (+) charged
Au --> Au + 3e
...we see that the Au charge went from 0 to +3 (s) (s) +3 +2 (s) (s) - +3 +2 - +2 (s) *THE AGENT IS ALWAYS THE OPPOSITE OF THE HALF REACTION* An "agent" is what oxidizes or reduces a reaction. +2 Reducing Agent: whatever the oxidation is
...in the previous example we saw that the oxidation of this reaction:
Pb+2 + Au(s) --> Pb(s) + Au+3
the half reaction was..
Au(s) --> Au+3 + 3e-
the reducing agent of this oxidation reaction is opposite this! so Pb+2 is the oxidizing agent which causes Au(s) to reduce C! Way To Go! B! Super Job! You must have been taught well! How do you find an oxidation number you might ask? We'll tell you! Here's a few simple rules you should follow first!
Nic & Nilams' Rules To Finding Oxidation Numbers:
1. Oxidation number of a free element is always zero. (O , S , P )
2. Oxidation number of single ion is equal to the charge it has. (Cl = -1)
3. Fluorine is always -1
4. Oxygen is always always -2
5. Hydrogen is always always always +1
6. Groups of oxidation numbers are as follows:
a. Alkali Metal: +1
b. Alkaline Earth Metals: +2
c. Halogens: -1
7. the sum of oxidation numbers in a molecule is zero, the sum for an ion is the charge of the ion. What is an oxidation number?
..it is the charge that would be on an atom Na S 0 2 2 3 From Nic & Nilams' rules I now know that O = -2!
So...if I have 3 oxygens, its simply:
-2 (charge) x 3 (oxygens) = -6 -6 note there is no overall charge on the ion From Nic & Nilams' rules I also know that Na is a Alkali Metal so it is = +1! What a life saver these two fabulous kids are!
So...if I have 2 sodiums, its simply:
+1 (charge) x 2 (sodiums) = +2 +2 Since there is no charge on the ion, we know it must equal 0 in the end.
So...since we're certain about oxygen and sodium:
-6 + 2 = -4 --> we know that S must equal +4 to balance this out +4 2 Oh but wait, there's more! Its not over just yet! Since we are being asked for only S not S , we must divide it by 2 to get S on its own!
4 / 2 = +2! (bet you thought it was +4) Using Nic & Nilams' Rules lets try an example! What is the oxidation number of S? 2 so.. S = +2 ! How do you predict whether there is an oxidation or reduction now a days?
If the element on the left is higher than the element on the right, then a redox reaction will occur and be spontaneous. If both elements are on the same side of the table, or the right side is higher then the left, it will be non-spontaneous.
remember..if it is increasing as a oxidizing agent, the reaction is a reduction
if it is increasing a reducing agent, the reaction is a oxidation
lets look at an example! What are standard reduction potentials?
They tell us whether or not a redox reachtion will be spontaneous or non-spontaneous. You may ask how we are to tell this? Not just by assuming because we know what happens when you ASSume. We use the chart of course! left side of table is increasing strength going up the table and increasing as an oxidizing agent right side of table is increasing going down the table and increasing strength as a reducing agent Metals are located at the bottom except for a few. Halogens/oxyanions are at the top. Some metals maybe have more than one oxidation number causing there to be more than one half reaction on the table! BE CAREFUL OF THIS! Make sure when dealing with lone half reactions you use equilibrium arrows because they can go forward and backward. Is the following reaction spontaneous?
Fe + Sr --> Fe + Sr 2+ 2+ the reduction is:
Fe + 2e --> Fe
so..this is the oxidizing agent the oxidation is:
Sr --> Sr + 2e
so..this is the reducing agent 2+ - +2 - we see its higher on the left
and lower on the right, so yes
this is a spontaneous reaction! C! Super! C! Right again! Did you ever wonder how to balance a FULL redox reaction? Yeah..me neither! But here's a few steps on how to do so! Brought to you by the same fabulous pair that brought you oxidation number rules, Nic & Nilam!
Nic & Nilams' Steps To Balancing A Full Redox Reaction:
1. Separate equation into two half reactions. Major atoms should be separated.
2. Balance the half reactions.
3. Multiply the half reactions to ensure the electrons balance properly. NO EXTRA ONE EHH!
4. Now add them together and cancel the electrons and anything else in common. **if it so happens it is in a basic solution use water to cancel out the H+’s! Electrochemical Cell:
to measure the number of volts of a electrochemical cell, you connect a voltmeter in route of electrons flowing from the anode to the cathode which will measure the volts.
Electrode: conductor when a half reaction happens ANODE CATHODE Anode: electrode when oxidation happens towards the anions Cathode: electrode when a reduction happens towards the cations D! Great! A! C! A! Correct! C! C! Trial Keq or "Q":
the trial value of Keq is not the REAL Keq
value, its is just a calculated number that helps us know which way a reaction shifts
-Q < Keq = shift right to products
-Q > Keq = shift left to reactants Keq: Equilibrium Concentrations: BUT like everything else in life there are usually some exceptions..just to throw you off:
HALF CELLS NOT AT STANDARD CONDITIONS:
will decrease reduction potential if the concentration is decreased less than 1M
will increase reduction potential if the concentration is increased more than 1M
Once the cell has reached equilibrium, it goes to 0.0V and the battery dies. Voltage or Electrical Potential: the rate of work done by the voltage per electron transferred at which electrons are flowing in an electrochemical cell.
In a half reaction that happens to be reversed, the sign of its E^0 is reversed (-) instead of (+) Cell potential can be calculated by..
E^0 cell = E^0 red - E^0 ox
What does this mean you may ask?
energy of the cell = energy of the reduction - energy of the oxidation
Where do I get numbers to put into the formula?
Once you know which is the reduction and which is oxidation, voltages can be found on your chart!
If E^0 cell is POSITIVE in a redox reaction it should be spontaneous
If E^0 cell is NEGATIVE in a redox reaction, the reaction is non-spontaneous
Surface areas have no effect on cell potential! -Inert electrodes can be used when ions, liquids, or gasses in a half reaction are present.
-Increasing the amount of electrode material will make the cell last longer. BIGGER BATTERIES LAST LONGER! lets see all this talk in action:
Pb+2 + Au(s) --> Pb(s) + Au+3
ox: Au(s) --> Au+3 + 3e-
red: 2e- + Pb+2 --> Pb(s)
ox: Au(s) = +1.0
red: Pb+2 = -.13
E^0 cell = (-.13) - 1
= -1.13 D! B! D! Like Mr. E with some of his students, some half cells are not at saturated state so they might need a bit of a "extra push" with more voltage! Its possible to have many different reactions going on in a cell. The one highest on the left side of the chart and the one on the lowest right hand side of the chart is the strongest reaction and is liked the best.
Follow Nic & Nilams' 3 "Do It Yourself" Steps:
1. List everything present including ionic solutions separated into ions
2. Find highest on left and lowest on right
3. This reaction you now have will occur
ELECTROLYSIS: giving electricity to a molten ionic compound or possibly a solution with ions so it produces a chemical change
ELECTROLYTIC CELL: where electrolysis can occur inside -Rusting applies to the oxidation of iron, whereas corrosion is the oxidation of any other metals.
-The big boys in charge of rusting iron are water and oxygen.
-When water sits on iron, a spontaneous reaction happens
-Anode is the O2 area lacking in O2
Fe --> Fe+2 + 2e-
-Cathode is the O2 rich area.
1/2 O2 + H20 + 2e- --> 2OH-
-Fe+2 joins OH- and makes Fe(OH)2 which oxides to Fe2O3 Ever wonder why a car gets rust built up on it after a while? Yes? Great! No, we'll tell you anyway! So kids if you're ever going to by a car, and don't want it to look like that, here's how to prevent it!
-coat metal with paint or plastic protector (purple is a great color for any car!)-put a metal that is corrosive resistant to the surface of the metal, for example zinc! D! Your awesome! * hint if you remember reading about a
purple car..you should know this! B! Acid: ionic compound that starts with "H" ex. HBr, H3PO4
Base: ionic compound that ends with "OH" ex. NaOH, Fe(OH)3
Salt: ionic compound that neither starts with "H" nor ends with "OH" ex. CaCO3, BaSO4 General Properties of Acids and Bases:
Properties of Acids:
a) acids react with bases
b) acids are electrolytes
c) acids react with some metals (Mg, Zn) to produce H2(g)
d) acid turns litmus paper red
e) acids taste sour (ex. lemon juice, vinegar)
Properties of Bases:
a) bases react with acids
b) bases are electrolytes
c) bases feel slippery
d) bases turn litmus paper blue
e) bases taste bitter The Truth Behind H+(aq):
Hydrogen atoms have protons surrounded with one electron. If it is removed, we now have a naked proton. This high concentrated positive charge is very much so attracted to anything negatively charged.
Proton: is an H+
Hydronium Ion or Hydrate Proton: is H30+ where water is added.
ON A SIDE NOTE: H+ can now also be written as H30+ Now that we know what solubility is how do we calculate it?
-Solubility is calculated in mols/L or simply M (molarity)
-[ ] square brackets are used to show concentration
-knowing stoichiometry is helpful A salt will always break apart into ions when it dissolves in solution (NaCl --> Na + Cl). When we calculate solubility we are looking to calculate the concentration of all the ions present.
NaCl --> Na + Cl
.1M .1M 1M Types Of Acids:
Monoprotic Acid: supply only one proton - HCl
Diprotic Acid: supplies two protons - H2SO4<---examples from notes
Triprotic Acid: supplies three protons - H3PO4
Polyprotic Acid: can supply more than one proton - H2SO4
Amphoteric Substance: can act as either an acid or a base. examples from notes... H20, H2PO4-, HS-A substance is amphiprotic if it has an negative charge, and has a removable hydrogen. Conjugate Acids and Bases:
Conjugate Acid-Base Pair: a pair of chemical parts which are only different by one proton
Conjugate Acid: part of a conjugate pair which has one extra proton
Conjugate Base: part of conjugate pair which doesn't have the extra proton
REMEMBER: organic acids end in COOH and the H is acidic
Organic bases have NH3 or an NH group. The nitrogen accepts an extra proton
...basically its just a proton transfer
ex. acid= H2O2 base= HO2-
acid= H3BO3 base= H2BO3- What do strong acids and bases do?
Strong Acid and Base: an acid or base which is 100% ionized in solution Weak Acid and Base: an acid or base which is less than 100% ionized in solution
Weak and strong refer to the percentage of ionization.
Dilute and concentrated refer to the molarity of a solution. The Acid Base Table:
Some other things noticable on the table
1. higher an acid on the left the stonger the acid
2. lower a base on the table the stronger it is
3. stronger the acid the weaker the conjugate base
4. when an acid is with water, H3O+ is produced
5. when a base is with water OH- is produced
Leveling Effect: we can say water has levelled all the strong acids to the same strength therefore the strongest acid that can exist in aqueous solution is H30+ vs. Bronsted_Lawry Definition Of Acids and Bases:
Acid: a substance that donates a proton
Base: a substance that accepts a proton Relative Strengths Key Points:
-When you have two acids, the stronger one out of the two will be more successful in donating a proton than the weaker one because in a way, it wants to give one away more than another.
-If your dealing with a bronsted lowry acid base equilibrium, the side that has the weaker acid will be more favored. (Think Le Chatalier's Principle!) weak bases: found on the right side of the table in the white section
So Strong Acids: are the top 6 acids on the relative strengths of bronsted-lowry acids and bases.
Strong Bases: can be found on the lower right side of the table, all metal hydroxies are 100% dissociated in solution making them a strong base.
The weak acids: on the left side of the table in the white section There are 3 ways to express a precipitation reaction:
Formula Equation: all reactant and product ionic compounds are balanced
Total Ionic Equation (Complete Ionic Equation): all soluble ionic compounds are broken down into individual ions; the solid non-soluble ionic compound stays as a compound and does not
Net Ionic Equation: the overall balanced equation that shows only ions present in the reaction and the solid that is formed, all other ions are known as "spectator ions" that just get cancelled out The Solubility Product:
-In dynamic equilibrium we learned about the Keq expression [producuts/reactants], now we learn that Keq=Ksp and Ksp is simply, Ksp=[products]
-Ksp = the Solubility Product Constant (solids are still omitted from the Ksp equation)
-The two ways you will learn about Ksp is by solving for Ksp when you are given concentrations of ions or by solving for ion concentrations when you are given Ksp Common Ion Effect:
-when you lower the solubility of a salt by adding in another with a common ion
-this has a relation to Le Chatalier’s principle <-- Hey what’s up buttercup?! We would just like to let you know that you’re a dump truck load of OK! Honestly, literally, actually, for real though, it’s been a phenomenal semester in Chemistry 12 with the good old Mr. Eckert and the most unbelievable majestic learning experience we have ever been part of! Our brains are all now watered with your Tim Horton’s Double Double love from the roots when we were planted in September to now in January where we have blossomed into sweet bright red Oklahoma, Oklahoma, Oklahoma, Oklahoma apples. We are now ready to be distributed across the world into many different pathways your students chose to go into. On behalf of all the cool kids in Chemistry 12, Block Four at Clayton Heights Secondary School in Cloverdale Canada, THANK YOU FOR BEING SO AWESOME!! A! C! Predicting The Solubility Of Salts:
Is there a difference between soluble and low solubility?
Yes there is! A substance with low solubility has a salt concentration of less than .1M in saturated solution, so it will form a precipitate. A soluble substance does not form a precipitate. Predicting Whether A Precipitate Will Form:
-Like we have learned in dynamic equilibrium we know we can create a trial value (Q) for Keq to compare!
-The first step is to disassociate the equation into its ions. Say we are using NaCl for example.
NaCl --> Na+ + Cl-
-Now we can write out the Ksp expression, and compare the actual Ksp to the trial.
-Q<Ksp a precipitate will not form
-Q=Ksp a saturated solution is formed
-Q>Ksp a precipitate will form D! Arrhenius Definition Of Acids And Bases:
Acid: a substance that releases H+(aq) in solution
Base: a substance that releases OH-(aq) in solution
Salt: is an ionic compound produced when the acid and base react making it neither acid nor base: acid + base --> salt + water
ex. HCl + NaOH --> NaCl + HOH D! C! HYDROLYSIS
Hydrolysis: reaction that produced an acidic or basic solution from a salt and water reaction.
ALL SALTS ARE 100% IONIZED IN WATER
First off, we need to find ions that do not react in water to make an acidic or basic solution, known as spectator ions.
Spectator ions: conjugate ions of strong acids or bases and do not take part in the reaction. They spectate, get it? Haha classic
Spectator Cations: ions of alkali metals, and alkaline earth metals
Spectator Anions: First five anions at the top right of the acids and bases table
What to do to figure out the behavior of a salt in water:
1.Find ions made when salt dissociates
2.Ignore the spectators
3.For the rest of the ions that remain
a)they will act as an acid if on the left side of the table
b)they will act as a base id on the right side of the table.
EXAMPLE: KCl <--> K+ + Cl- This is neutral
NH3 + H2O <--> NH4+ + OH- This is basic Calculations Involving Kb:
When weak bases are put into water, some of the base will ionize. This means some OH- is produced. The higher Kb, the more OH-
Calculations are similar to weak acids but with two changes:
-Kb has to be calculated and cant be taken from the table unless you previously took the time to calculate them all, like us smart kids do.
-Solution left over will be basic which means [OH-] will be used rather than [H30-] The Equilibrium Constant For The Ionization Of Water:
Acidic Solution: [H30+] > [OH-]
Basic Solution: [H30+] < [OH-]
Neutral Solution: [H30+] = [OH-]
SELF-IONIZATION OF WATER: H20 + 59KJ <--> H+ + OH- OR 2H2O + 59KJ <----> H30+ + OH-
Equilibrium Expression (Kw) at 25 degrees Celsius: Kw= [H+][OH-] = 1.00X10 -14^
OR Kw= [H3O+][OH-] = 1.00X10 -14 Calculations Involving Ka:
When a weak acid like HA is put into water, some acid ionizes. Afterward a certain amount of H3O+ is made. The amount made depends of the Ka value of the weak acid. To solve these problems we use something called an ICE TABLE like we saw in equilibrium! See how much its all connected?
You will need: -[HA], or the original concentration of the weak acid-Ka of the acid-finally [H3O+] or the pH of the acid solution. pH and pOH:
pH = -log[H3O+] pOH = -log[OH-]
pH scale: 0------------------7----------------14 pOH scale: 0------------------7--------------------14
Acidic neutral Basic Acidic Basic neutral
Heres a chart to help us show what to do to find what: -When temperature is increased the concentration of H30+ AND OH- is increased along with the electrical conductivity
-When temperature is decreased the concentration of H30+ AND OH- is decreased along with the electrical conductivity
Kw will stay as a constant if [H30+] increases and [OH-] decreases OR, [H30+] decreases and [OH-] increases.
For example, If water is added, [H30+] will increase and cause the water equilibrium to shift to use up more H30+ The greater the value of Ka, the stronger the acid....... just sayin!