Equilibrium Flashcards

• Microscopic properties are continuously changing (molecular level) while microscopic properties are constant in equilibrium (e.g. pH, temp, and other observable properties). Dynamic equilibrium means that the fwd and rev rxns are occuring at the same rate so macroscopic properties and concentrations are constant (change is occuring equally microscopically), if we can observe change the solution is not in a state of dynamic equilibrium. Requirements for this are that the temp must remain constant (or else Kc changes) and the system must remain closed.
• Three examples are solubility equilibriums (saturated solutions with excess solide), State equilibriums (e.g. water and ice) and chemical rxns at a constant temp. (e.g. soda)

• Homogeneous expression means that the state is the same (aq, gas or liquid...solid state is not useful in equlibrium) Heterogeneous expression means diff. state.
• The rules for equilibrium law expression (Kc) is that concentrations are always in mol/L, product concentrations are always in numerator while reactant concentrations are always in denominator and concentrations are always raised to the power of the coefficients in the balanced chemical eqxn for the rxn. Lastly Always include gaseous and aqueous solutions, only include liquids there are 2 or more (include all if this is the case, leave out if theres 1) and never include solids.

Whats favoured?	Concentration of products vs reactants at equilibrium	Corresponsing arrow and percent rxn
Products/rxn fwd	[products]>[reactants]	⇋ (>50% on top)
Ractants/rxn rev	[reactants]>[products]	⇋ (<50% on top)
Quantative	>99% products	-->

• Since Kc is a ratio of products/Reactants at equilibrium it means the larger the Kc the more products at equilibrium, the smaller the more reactants at equilibrium.
• If Kc is much greater than 1 that means products could dominate at equilibrium and that the equilibrium favours the products, if Kc is much less than one then reactants dominate and are favoured. If Kc = 1 then products and reactants could be the same concentration.

Equilibrium law expression is limited in the fact that it does not provide info on th rate of rxn (does not tell if a catalyst was used), it changes depending on temp and that percent rxn changes depending on the concentration of the reactants.

In equilibrium graphs the x-axis is the time or rxn coordinate, the y-axis is the concentrations of the reactants and products. In the beginning the concentration of reactants is decreasing and products are increasing and the rate of decrease/increase is porportional to the coefficients of the eqxn. In these graphs equilibrium is only reached if all lines are parallel. We can use this info to determine Kc after the graph reaches equilibrium.

• For any closed chemical system the tendency is to move towards equilibrium. Le Chatelier's principle states that when a system at eq is disturbed by a change (stress) it adjusts in a way that opposes the change (opposes stress). This is a 3 step process:
• 1. the system is at an initial eq state 2. a stressor is added causing a non eq state 3. the system moves to a new eq state. Types of stresses are adding/removing reactants/products, changing volume/pressure (for gases) and changing the temperature. There are two types of eq shifts. A right shift is when the [product] increases because the fwd rxn is momentarily favoured and a left shift is when the [reactant] increases because the rev rxn is momentarily favoured.

These graphs are shown in concentration throughout rxn progress graphs. In these graph's there is a line for each of the products and reactants, in which changes can be seen. We can identify 3 types of changes: 1. Heat, these changes will all be gradual change because of the time it takes for heat to be absorbed which will cause a slow shift, 2. Pressure/volume, these are all sudden as there is a sudden increase/decrease in the moles/L of something and then a shift occurs to equilize, 3. concentration, we will only see one sudden change - of the substance being added/removed and then the others will have gradual changes as they move towards eqb.

They are tables that allow you to calculate changes of other substances equlibrium from the information of one. Start by filling the I row with information you know (usually product concentration is 0). Next in the change section write the coffecient of the substance in the balanced chemical rxn followed by x, x denotes change - it is neg. for reducing concentrations and pos. for increasing. Lastly in the equilibrium sectiom write the ending concentrations that your are given. Then solve for x by using the rule initial + change = equilibrium and use that to find out other values, once you solve the equilibrium section of the table you can calculate the new Kc. Don't forget to divide concentrations by your volume!

• Acids turn blue litmus red, conduct electricity (ionization), Taste sour and react with metals to produce H2(g) (make bubbles). Bases turn red litmus blue, conduct electricity (only strong bases cus dissociation), taste bittery, feel slippery and do not react with metals. 
• A conjugate acid-base pair are a pair of substances that differ by only one H+(aq). Amphiprotic means a substance that can act as either an acid or base in different situations, ex: water, HCO3-(aq), HSO3-(aq).

Arrhenius theory defines acids as substances that ionize in water to produce H+(aq) and bases dissociate to produce OH- (aq) in water. Modified Arrhenius states that acids react with water to make H3O+(aq) ions and basic solutions are formed when substances react with water to form OH-(aq) ions. Bronsted-Lowry is a theory used for acid-base rxns together whereas modified arrhenius is used for acids and bases when they are alone. Bronsted Lowry states that acids are substances that donates protons and that a base accepts protons.

• 1. Make a species list (Ionize all strong acids into H3O+ and the negative ion and dissociate all soluble ionic compounds, remember that WA's and molecular compounds don't seperate into ions)
• 2. look at your acid base chart and find the strongest acid (closest to top left) and strongest base (closest to bottom right).
• 3. transfer a H+ from the acid to the base to determine the products.
• 4. Use appropriate arrows (Products favoured: ⇌+>50%, Reactants favoured: ⇌+<50%, Quantative (will say in question or used when hydronium is reacting with hydroxide): -->)

With very precise meters it is possible to see a little bit of conductivity. This means there must be ions present, therefore water must ionize a small amount (2 in a billion). Then it is 2H2O (eq arrow) H3O+(aq) + OH- (aq). This also means it has an equilibrium and therefore we can calculate a constant. Kw=P/R =[H3O+][OH-] Kw (water equilibrium) is 1.0x10^-14.

In acids: [H3O]>[OH] In bases: [H3O]>[OH] and in neutral solutions: [H3O]=[OH]. pH = -log[H3O+]. [H3O+]=10^-pH. pOH= -log[OH]. pH + pOH=14. Remember the pH scale operates in factors of ten so going from a pH of 6 to 3 is 1000x more acidic.

It means a rxn favouring the reactants or a very small amount of hydronium/hydroxide ions being made. To calculate use the formula Ka=[H3O+][conjugate base]/[acid]. Using an ICE table we can come to the shortcut Ka=[H3O+]^2/[acid]-[H3O], , because the concentrations of H3O+ and conjugate acid is the same and because the acids equilibrium concentration is just the prior concentration minus how much was made into products. Kb=[OH-][conjugate acid]/[base] and the shortcut is Kb=[OH-]^2/[base]-[OH].

Since weak acids and bases have such little reaction with water, the changes in concentrations are often negligible. This means we can ignore the change from final to initial concentration (Ci) if Ci/Ka >1000.Meaning we can simplify Ka=x²/Ci-x to Ka=x²/Ci.

If we multiply the formulas for two conjugate acids and bases we end up with everything accept water cancelling out. This means KbKa=Kw. Therefore we can use our data booklet to find the Kb's of conjugate bases by dividing Kw by Ka found in our data booklet. Then we can use Kb to find the concentration of OH- and then -log[OH-] to find pOH and finally 14-pOH to find pH.

First we dissociate the ionic compound and write the species list, then we check our table (data booklet) and find the strongest acid and then the strongest base (present) the acid can react with, since one of these is usually water (as the other part of the ionic compnd is usually a spectator) we can create a Bronsted-Lowry eqxn and then use an Ice table and  KaKb=Kw to figure out [OH-] and then find pH. When the compound is amphiprotic, if it is closer to the top of the acid side it is an acid, if it is closer to the bottom it acts as a base (e.g. NaHCO3 is basic).

A monoprotic acid is an acid that only donates one H+ to the base, while a monoprotic base can only accept one H+. A polyprotic acid can donate more than one proton to the base (diprotic if 2, triprotic if 3) and a polyprotic base can accept more than one proton (Dibasic or Tribasic usually).

For the graphs you draw an s shaped graph with as many endpoints (the colour/property change - middle of the steep portions) as stated and then label the buffer zones (plateaus, where pH change is resisted) and label the inflection points (where pH change begins to ramp up). Remember the top plateau is not a buffer zone as that is where you stop adding the titrant so the reactants have not been removed. An endpoint has to do with pH while and equivalence point has to do with volume.

First you write a Bronsted lowry equation for each endpoint, these will have quantative arrows. Then if the product from the last endpoint can still donate/accept H+ create another equation, this time with an equilibrium arrow as this reaction is theoretical and has not occurred yet. Lastly, write a net reaction where the reactants from the very beginning react to form the products from the last endpoint. Do not inclue the products from the theoretical reaction.

They are complex weak acid/base compounds that change colour depending on [H3O+] showing the endpoint of an acid-base titration, most are organic acids with complicated structures so we abbreviate, HIn is the general formula for their acid form and In- for their base form. They are always in the same form (acid/base) as the solution they are in. E.g. In an acidic solution the rxn formula is H3O+(A) + In-(B) -> HIn (CA) + H2O (CB), in this solution the indicator is in acid form, while in base form the formula is: OH- + HIn -> In- + H2O. The general formula for an indicator rxn is  HIn + H2O -> H3O+ + In-.

• 1) you can figure out whether the titrant/sample is an acid/base
• 2) You can find the equivalence/end point by looking at the midpoint of the steep areas and the buffering areas by looking at the plateaus (except the theoretical/last one). DF that each steep area (end/equiv point) shows an acid/base reacting quantitatively. This is because as a general rule only quantitative rxns produce findable endpoints in a titration, therefore endpoints=quantitative rxns.
• 3) We can also choose an indicator for each endpoint. The endpoint range should be as close as possible to the midpoint of the indicator range.

• Depending on the starting pH of the graph we can tell what the original solution is (in terms of acid or base). pH around or above 14 = strong base, below 14 but above 7=WB, below 7 but above 1=WA and below 1=SA.
• Then from the endpoints we can tell what was being added. If the pH is above or below 7 it is one strong thing being titrated with something weak (depending on starting pH) and If it is around 7 then it is strong + strong or weak +weak depending on starting pH's. Additionally weak rxns will not have totally steep and perfect endpoints.

They are solutions that resist a pH change, when small amounts of acid or base are added. They are composed of a weak acid and its conjugate base mixed together at equilibrium. The conjugate base will react with H3O+ ions from SA's to resist a pH change and the conjugate acid will react with OH-'s.

• Water in the atmosphere react with NOx,COx and SOx causing acids to form and rainwater to be slightly acidic. The gases come mainly from combustion. This rain is harmful to the enviroment, organisms and corrodes away at infrastruture.
• To prevent it we can use scrubbers (equipment that remove sulfur dioxide from combustion by using a WB), catalytic converters(found in all cars, reduces NOX, CO and hydrocarbons by turning them into CO2,N2 and H2O) liming ( adding calcium carbonate (limestone) or magnesium carbonate to lakes in order to help them neutralize acidified water) and more.