Determine the force in each member of the truss and state if the members are in tension or compression. 2 kip 1.5 kip 4 ft 10 ft 10 ft 10 ft 3 kip 3 kip 10 ft A B I H G F C D E 8 ft Prob. 64
Review for Chemistry 121 B Professor: Dr. Thomas Holovics Southern Illinois UniversityEdwardsville Chapters 14 &15 Test Date: March 3, 2016 Referencing back to the blue lecture notes book Chapter 14 Chemical Equilibrium Key terms, vocab, equations What does “Equilibrium Constant” mean o when the amount of the products are relatively the same as the amount of reactants What is the definition of “Dynamic Equilibrium” o When the rates of the forward and revers reactions are equal. What is the formula for Equilibrium Constant, Kc o Kc=[C]^c[D]^d/[A]^a[B]^b Where C & D are the products and A&B are the reactants So, concentration of Products or the concentration of the reactants How do we know if the products are favored or if the reactants are favored o If K is larger than 1, then the products are favored. If K is smaller than 1, then the reactants are favored. There is an example of a problem finding if the reactants or products are favored in the lecture note book page 138 When referring to a reverse reaction, what does K’ (K prime) stand for o It is the reciprocal of K There is an example problem of this on page 140 and 141 Equilibrium Constant o If you add the given equation, you get the desired equation. o If you multiply the given K values, you get the equilibrium constant for the overall reaction. What is the formula for partial pressure equilibrium constant o Kp= (PG)^p(PH)^h/(PA)^a(PB)^b Partial pressure of the products over the partial pressure of the reactants How is Kp Related to Kc o Kp=Kc(RT)^Δn T is temperature in Kelvin R=.08206 Δn is the difference in the number of moles of reactants and the moles of products Kp=Kc when Δn=0 Partial pressure is always in ATM o There are example problems for this on page 145 Kc does not work for solids or liquids because their concentrations do not change. o The amount of solid and liquids may change but the concentrations do not. What is the most direct way to find equilibrium constant o To measure the amounts of reactants and products at equilibrium Equilibrium constant is independent of the initial amount of reactants or products. For Nonequilibrium conditions, instead of using Kc or Kp, you use o Qc or Qp What is the Qc or Qp used for o For prediction the direction of the net change of the reaction. To do this, compare the magnitude of Qc to Kc Qc vs. Kc No Products/ Reactants K>>Q Products Formed Shifts Right K is much larger than Q Products/ Reactants K>Q Products Formed Shifts Right K is larger than Q Products/Reactants K= Q No Products or Does not Shift K and Q are at Reactants Formed equilibrium Products/Reactants K.05 Example on page 158 Le Châterlier’s Principle helps us predict the effects from various changes in equilibrium conditions o Meaning, if the equilibrium is disturbed, then the position of equilibrium will shift as to minimize the disturbance. o Example: You have two countries right next to each other, A and B. A and B are at equilibrium. But then some people from A move over to B, making it have more people. Now the equilibrium is messed up and B is a bit crowded. So, to fix this, some people from B move to A, making then equal again. o Equilibrium shifts away from the side with added stuff. OR Equilibrium shifts towards the side with removed stuff. There is an illustrated example of this on page 161 Does Adding a gas reactants increases the partial pressure causing the equilibrium to shift to what side o Right Increasing the partial pressure increases the concentration but it does not increase the partial pressure of other gases in the mix Does adding or removing pure solids or liquids affects the equilibrium o No, they do not. When the external pressure is increased equilibrium shifts which direction o In the direction producing the smaller number of gas moles When the external pressure is decreased equilibrium shifts which direction o In the direction producing the larger number of gas moles If there is no change in the number of gas mole what effect does the change in external pressure have o It has no effect. __________ the temperature of an equilibrium mixture shifts the equilibrium in the direction of the endothermic reaction. o Raising Lowering the temperature of an equilibrium mixture shifts the equilibrium in the direction of the _________reaction. o Exothermic Consider heat as though it is a product of the endothermic reaction and a reactant of the exothermic reaction o This is a really nice summary diagram for this on page 165 And an example equation Remember: adding a catalyst will lower the activation energy of both the forward and revers reaction BUT it does not affect the equilibrium state. A standard example table of Disturbing equilibrium Adding more Shift to the Right Shift to the Left No Change product Removing some Shift to the Right Shift to the Left No Change reactant Increase in Shift to the Right Shift to the Left No Change Temperature Decrease in Shift to the Right Shift to the Left No Change Pressure Adding a catalyst Shift to the Right Shift to the Left No Change Le Châterlier’s Summary Change Effect Concentration Increase in [reactant] or decrease in [product] favors forward reaction Partial Pressure Increase in [product] or decrease in [reactant] favors revers reaction Temperature Increase in temp. favors endothermic reaction Decrease in temp. favors exothermic reaction Pressure Increase in pressure favors side with less gas moles Decrease in pressure favors side with more gas moles Volume Increase in volume favors side with less gas moles Decrease in volume favors side with more gas moles Catalyst added Equilibrium reached faster. Make sure to do the selftests on pages 143, 155, and 167 Chapter 15 Acids and Bases Fun Fact: Mild Heartburn can be cured by neutralizing the acid in ones esophagus. Acids o Taste sour o Can dissolve many metals o Neutralizes bases o Change blue litmus to red o Some common acids Sulfuric Acid, Hydrochloric Acid, Nitric Acid, Acetic Acid, Citric Acid, Carbonic Acid Bases o Bitter taste o Feels slippery o Turns red litmus paper blue o Neutralizes acids o Common bases Sodium hydroxide, Potassium hydroxide, Sodium Bicarbonate, Ammonia, Sodium Carbonate Arrhenius Theory Definition of acids and bases Svante Arrhenius o Bases off of H+ and OH H+ is for Acid and OH is for bases (18591927) BrønstedLowery Definition o Based in reactions win which H+ is transferred Lewis Definition o Based on the reaction in which lone pairs are transferred Arrhenius Acids and Bases o Arrhenius Acid is a compound that ionizes in H2O to form a solution of ____________ H+/H3O+ ions and anions o Arrhenius Base is a compound that ionizes in H2O to forma solution of _____________ OH and cations Just to be clear, what is the definition of neutralizing o It is the process of an acid reacting with a base to form H2O and an ionic salt. And what is an ionic Salt o It is the combination of the cation from the base and the anion from the acid What are some problems regarding the Arrhenius Theory o It does not explain why some molecular substances dissolve to form basic solutions even though they do not contain OH ions o It does not explain why some molecular substance dissolves to form acidic solutions even though they do not contain H+ ions. o It does not explain acidbase reactions that take place outside of (aq) solutions. BrønstedLowery Acids and Bases o A BrønstedLowery Acid is a ______________. Proton Donor Johannes N. Bronsted o A BrønstedLowery Base is a _______________. Proton Acceptor (18791947) o What is a conjugate base It is an acid minus the proton it donated. o What is a conjugate acid It is a base plus the accepted proton o The base accepts the proton and becomes a conjugate acid. o The acid donates the proton and becomes a conjugate base. There is a picture to show you the reaction on page 174 Lewis Acids and Bases o A Lewis Acids electron pair acceptor o A Lewis Base electron pair donor o The base donates the LP electrons to the acid. Gilbert Newton Lewis (18751946) Normally, a covalent bond forms The product formed is called an ______ In organic Chem, Lewis acids are An adduct o Arrhenius and BrostedLowery are also Lewis called electrophiles and Lewis reactions. bases are called nucleophiles There is a very nice diagram that visually explains this on page 176 How to identify Acids Binary Acids General formula: HX Examples: HF,HCl,HBr,HI, H2S, H2Te Complex Acids General Formula: Hx(Poly) Examples: HNO2, H2SO4, Oxoacids (H,O, and 1 HCN, H2CO3, H3PO4, other) HOBr, HClO2, HNO3 Organic Acids Gen Formula: RCOOH Examples: HCOOH, CH3COOH,C2H5COOH, C6H5COOH Lewis Acids Gen. Formula: M+ Examples: Fe+3, Hg+2, Incomplete octets/open Cr+2, H+ BF3,AIH2 orbitals Ions as Acids Positive ions can be acidic Examples: NH4+, Some anions of complex C5NNH+, HONH3+, acids HSO41, HCO31, HPO42 How to Identify Bases Metal Hydroxide Gen. Formula: MOH Examples: NaOH, LiOH, KOH, Ca(OH)2, Mg(OH)2 Amines Gen. Formula: Amines Examples: NH3, CH3NH2, C5H5N, (CH3)3n, HONH2, (CH3)2 NH Lewis Bases Has a lone pair that can easilyExamples: (NH3), CN, H2O be donated Ions as Bases Negative ions can be basic Examples: CO32, CLO2, HS, CN, PO43, CH3O, NO2, CH3COO0, F What is the name for the substance that can act as either an acid or a base o An Amphoteric substance They can do this because they have both a transferable H and an atom with Lone Pair Electrons. What is the most common amphoteric substance o That’s right, water. Good ol’ H2O A strong acid or strong base are strong electrolytes o Basically 100% acid molecules ionize and all base molecules form OH ions. A weak acid or a weak base are weak electrolytes. Strong Acids o Hydrochloric Acid (HCL) o Hydrobromic Acid (HBr) o Hydriodic Acid (HI) o Nitric Acid (HNO3) o Perchloric Acid (HClO4) o Sulfuric Acid (H2SO4) All other acids are weak Measure an acid or base’s strength by using the equilibrium constant. The stronger the acid is at donating H, the weaker the conjugate base is at accepting H. Higher oxidation number= stronger oxyacid Cation is stronger that neutral molecules which are stronger than anions o H3O+>H2O>OH Base strength trend is the opposite Binary Acids o Strength increase to the right across the period and down the column So, Iodine (I) is the best Oxyacid, HOY o The more electronegative Y, the stronger the acid o Acidity increases to the right and up a group o The larger the oxidation number of the central atom, the stronger the oxyacid o The more oxygens attached to the Y, the stronger the oxyacid Carboxylic Acids o RCOOH o The more electronegative the R group, the stronger the acid Page 185186 has a huge list of Acids and Bases. It’s worth checking out Acid Strength is measured by the equilibrium constant o Larger Ka= Stronger Acid Ka= [H3O+][A]/ [HA]= [H+][A]/[HA] Neutral Solutions have _______[H3O+] and [OH] Equal Acidic solutions have ________[H3O+] than [OH] Larger Basic solutions have__________[ OH] than [H3O+] Larger pH is used to express acidity or basicity o pH= log[H3O+] o waters pH is –log[10^7]=7 o [H3o+]= 10^pH pH<7 is acid, 7 is neutral, pH >7 is basic o there is an example to find pH on page 191 Another way to express acidity/basicity is using pOH o pOH= log[OH] o [OH]= 10^pOH o You need to know the [OH] to find pOH o pH+ pOH=14.0 Another way is pK o pKa= log(Ka), Ka= 10^pKa o pKb= log(Kb), Kb= 10^pKb o smaller pKa= stronger Acid o larger Ka= smaller pKa Why Because it has a neg. log o Smaller pKb= stronger the base o Larger Kb+ smaller pKb Finding the pH for Strong o For monoprotic strong acids [H3O+]=[HAcid] o For strong ionic bases [OH]= (number OH ions)*[Base] o There are examples showing the work for these types of problems on page 195 Finding pH for Weak o HAcid+H2O Acid +H3O+ o Use the ICE table o You can use Neglect x o There are tons of examples on pages 196, 197, and 198. Acid Ionization o Another way to measure Acid strength. o To do this determine the percentage of acid molecules ionized when dissolved in water Called Percent Ionization o The higher the percent ionization, the stronger the acid o Percent Ionization= ((molarity of ionized acid)/(initial molarity of acid))*100% Example Page 199 A monoprotic Acid has one single ionizable H atom per molecule A polyprotic acid has more than one ionizable H atom Ions as Acids and Bases o Salts of strong Acids and Strong Bases form __________ solutions Neutral o Salts of weak acids and strong acids form _____________ solutions Basic o Salts of strong acids and weak bases form____________ solutions Acidic o Salts of weak acids and weak basics can form solutions that are acidic or basic or neutral It depends on the relative strength of the cations and anions o There are examples on page 202 DON’T FORGET TO DO THE SELFTESTS ON PAGES 187 AND 207 ALSO, maybe review the oxidation rules if you are rusty with those And what bases are strong or weak GOOD LUCK ON THE TEST!!! I BELIEVE IN YOU!!!