Spring 2016 Finals Study Guide AP Chemistry
Table f Cntents Sectin 1: Acids and Bases 1.1 Titratins 1.2 Indicatrs 1.3 Buffers 1.4 Slutin Preparatin Sectin 2: Calrimetry 2.1 Specific Heat 2.2 Metals Sectin 3: Gases 3.1 Ideal Gas Law 3.2 Gas Stichimetry 3.3 Limiting Reactant Page 2 Page 2-3 Page 3-4 Page 5 Page 5 Page 5 Page 5 Page 6 Page 6 Sectin 4: Precipitatin Reactin 4.1 Slubility Rules Page 6 Sectin 5: Lab Ntes 5.1 Titratin Lab 5.2 Are Yu Ka? Lab 5.3 Resisting Change Lab 5.4 Twice the Titratin Lab 5.5 Httest Lab Ever 5.6 (Dn t) Taste the Rainbw! 5.7 MW by FPD Lab 5.8 Speed f a Reactin 5.9 Qualitative Catin Lab Page 6-7 Page 7 Page 7-8 Page 8-9 Page 9 Page 9 Page 9 Page 10 Page 10 Page 1 f 10
AP Chemistry Final Exam Study Guide ACIDS AND BASES 1.1 TITRATIONS Frmulas t Knw ph + poh = 14 ph = -lg[h+] poh = -lg[oh-] [OH-]*[H+] = 1*10-14 n 1M 1V 1 = n 2M 2V 2 Percent Inizatin = (inized acid cncentratin at equilibrium) / (initial cncentratin f acid) Strng Acids: Hydrchlric Acid Hydrbrmic Acid Hydridic Acid Nitric Acid Sulfuric Acid Perchlric Acid Strng Bases: Grup 1 Hydrxides Grup 2 Hydrxides ph acids < 7 neutral = 7 bases > 7 Strng Acids and Strng Bases cmpletely inize in slutin H 3O + = Hydrnium 1.2 COMMON INDICATORS INDICATOR ACID COLOR BASE COLOR PHENOLPHTHALEIN Clrless Pink/Red BROMOTHYMOL BLUE Yellw Blue RED LITMUS Red Blue BLUE LITMUS Red Blue Page 2 f 10
UNIVERSAL INDICATOR Red/Orange/Yellw Blue/Vilet/Purple METHYL RED Red Yellw LITMUS (AZOLITMIN) Red Blue Yu prbably dn t need t knw these ff the tp f yur head, but it is still gd infrmatin t generally knw. 1.3 BUFFERS Buffer Basics Either... Weak Acid and It s Salt Weak Base and It s Salt Has the ability t resist change in ph upn the additin f small amunts f acid r base Graph Pint Calculatins Initial ph: ICE chart and K b r K a frmula Pint Alng Graph: mle chart and Hendersn-Hasselbalch Equatin Half-Equivalence Pint: ph = pk a poh = pk b Hendersn-Hasselbalch Cncentratin f Acid/Base = Cncentratin f Cnjugate Base/Acid (respectively) Equivalence Pint Mles f Acid = Mles f Base ICE Chart and K b r K a frmula In Excess: mle chart, find new cncentratin, ph r poh equatin Hendersn-Hasselbalch Acid: ph = pk a + lg ( [A ] ) [HA] Base: poh = pk b + lg ( [BH+ ] ) [B] Cmmn In Effect Shift in equilibrium caused by additin f a cmpund cntaining an in in cmmn with the disslved substance The presence f the excess ins frm the disslved salt greatly inhibits the dissciatin f the acid The psitin f the dissciatin equilibrium has been shifted left by the presence f the ins frm the salt PwerPint Ntes Adding a base t Buffer Slutin Steps 1) Assume the reactin ges t cmpletin and use stichimetric ratis YOU MUST CONVERT TO MOLES!!!! Page 3 f 10
2) Use the riginal equatin t carry ut the equilibrium calculatins CONVERT BACK TO MOLARITY!!! Vlumes are additive! Adding an acid t Buffer slutin Steps 1) Assume the reactin ges t cmpletin and use stichimetric ratis MUST CONVERT TO MOLES!!!! 2) Use the riginal equatin t carry ut the equilibrium calculatins CONVERT BACK TO MOLARITY!!! Vlumes are additive! Hendersn-Hasselbalch The equatin is useful fr calculatin the ph f the slutin when the rati f [A-] t [HA] is knwn Frmula: ph = pka + lg cnjugate base Buffer Slutins with Weak Bases B + H 2 O BH + + OH 1) The Weak base reacts with any H+ added 2) And the cnjugate acid reacts with any added OH- Cnvert mles back t mlarity and insert int the riginal equatin Alternatively We can btain the Ka value fr Ammnium frm the given Kb value fr NH3 Frmula: poh = pkb + lg acid cnjuagte acid Types f Buffer Slutins Type 1: Cmbine a weak acid with its cnjugate base Ex) HF and KF (a basic salt) Type 2: Cmbine a weak base with its cnjugate acid Ex) NH3 and NH4Cl (an acidic salt) Remember that NH3 can als be written as NH4OH Type 3: Add a limited amunt f a strng acid with an excess f a weak base. The result will be the same slutin as in type 2 Ex) add 0.70 mles f HCl t 1.0 Liter f a 2.0 M slutin f NH3. This will result in an excess f 1.30 mles f the base and generating 0.70 mles f the NH4 in Type 4: Add a limiting amunt f a strng base with an excess f a weak acid. The result will be the same as in type 1 Ex) add 0.50 mles f NaOH t 1.0 Liter f a 2.0 M slutin f HF. This will result in an excess f 1.5 mles f the acid and generating 0.50 mles f the F- in. Type 5: Prepare a slutin f an amphteric substance Ex) 1.0 M slutin f NaHCO3 base Page 4 f 10
1.4 SOLUTION PREPARATION Titratin Lab Resisting Change Lab 2 CALORIMETRY 2.1 SPECIFIC HEAT Definitin: The amunt f energy required t raise ne gram f a substance ne degree Celsius Frmula: q=mc p T May need t knw: q system = -q surrundings Temperature is a measure f the average kinetic energy f particles in a substance Heat is the sum f all kinetic energy f all the particles in a substance 2.2 METALS Every metal has its wn specific heat The identity f a metal can be determined by figuring ut the specific heat 3 GASES 3.1 IDEAL GAS LAW PV = nrt P- pressure V- vlume n- mles R- cnstant T- temperature Variatins PM = DRT PV = (m/m)rt Ideal Cnditins 1 atm, 22.4 L, 273 K, 1 ml Particles take up n space and n vlume N IMFs between particles Wn t liquefy (n vlume) Page 5 f 10
3.2 GAS STOICHIOMETRY At STP One mle f gas has a vlume f 22.4 L Vlume t vlume under any cnditins Avgadr s Law ( V 1 = V 2 ) n 1 n 2 All ther stichimetry Use ideal gas law (see page 5) 3.3 LIMITING REACTANT Limiting Reactant: a reactant that is cmpletely cnsumed during the reactin Excess Reactant: a reactant that remains after a chemical reactin stps The amunt f prduct that can be frmed is ALWAYS determined by the limiting reactant Adding mre f the excess reactant t a reactin wn t affect the reactin because it was already in excess. Hw t Find: Cnvert mles f bth reactants t ne f the prducts using dimensinal analysis 4 PRECIPITATION REACTION 4.1 SOLUBILITY RULES Sluble ALL nitrates, acetates, ammnium cmpunds, and grup ne salts Chlrides, brmides, and idides EXCEPT silver, lead, and mercury (I) Flurides EXCEPT grup 2, lead (II), and irn (II) Sulfates EXCEPT calcium, strntium, barium, mercury, lead (II), and silver Insluble Carbnates and Phsphates EXCEPT grup 1 and ammnium Hydrxides EXCEPT grup 1, strntium, barium, and ammnium Sulfides EXCEPT grup 1, grup 2, and ammnium Oxides EXCEPT grup 1 5 LABS (FROM AP) 5.1 TITRATION Backgrund Infrmatin Titratin: prcess in which the cncentratin f a slutin is determined by measuring the vlume f that slutin needed t react cmpletely with a standard slutin f knwn vlume and cncentratin Page 6 f 10
Prcess: gradual additin f standard slutin t unknwn Clr change f indicatr indicates end pint f titratin Indicatr used: Phenlphthalein Pink when basic Clrless when acidic Prcedure 25mL f HCl Slutin and 1-2 drps f indicatr int Erlenmeyer Flask Add NaOH gradually until slutin changes t light pink Recrd what the buret reading is befre and after the titratin Calculatins Mles f NaOH: multiply cncentratin by liters used Mles f HCl: ne t ne rati s it s the same as NaOH Cncentratin f HCl: mles f HCl divided by liters f HCl Average mlarity: yu shuld knw this ne 5.2 ARE YOU OKA? Pssible Indicatrs Phenlphthalein Clrless: 1<pH<8 Pink: 8<pH<10 Red: 10<pH<11 Methyl Red Red: 1<pH<5 Orange: 5<pH<7 Yellw: 7<pH<11 Orange IV Orange: 1<pH<3 Peach: 3<pH<5 Yellw: 5<pH<11 Pre-Lab Chemical Equatin Equilibrium Cnstant Expressin ph when [acid]=[cnjugate base] Chse an indicatr: why wuld phenlphthalein nt be a gd indicatr? Half equivalence pint is 2.12 5.3 RESISTING CHANGE Overview IMPORTANT: The Hendersn-Hasselbalch equatin allws the ph f a BUFFERED slutin t be calculated NOT just a slutin frm any acid r base reactin Remember, whenever H + r OH - ins are added t a slutin yu must calculate the new slutin cncentratins befre yu d anything else (mle chart) Hw t Prepare a Buffered Slutin f a Certain ph and Buffer Capacity Page 7 f 10
Figure ut which cnjugate acid-base pair t use fr given slutin The mst effective buffers have equal cncentratins f acid and base The pka f the chsen cmpund must be within + r 1 f the desired ph Calculate the desired cncentratin f the buffer Cncentratin f cmpnents f buffer determine the capacity f the buffer and thus yu must take int accunt t amunt f OH - r H + that will be added t the slutin 5.4 TWICE THE TITRATION Indicatrs Methyl Orange (pka= 3.40): Red (1-3) Transitin (3-4) Yellw (5-13) Methyl Red (pka= 4.95): Red (1-4) Transitin (4-6) Yellw (6-13) Phenlphthalein (pka= 9.40): Clrless (1-8) Transitin (8-10) Red (10-13) Brmthyml Blue (pka=7.10): Yellw (1-6) Transitin (6-8) Blue (8-13) Phenlphthalein (pka= 10.00): Clrless (1-9) Transitin (9-11) Blue (11-13) Lab Tips LABEL EVERYTHING!!! = helps keep track f slutins Always rinse glassware with DISTILLED r DEIONIZED water Basic Graphs Weak Acid with Strng Base Weak Base with Strng Acid Page 8 f 10
Strng Acid/ Strng Base 5.5 HOTTEST LAB EVER Backgrund Hess s Law: if the same verall reactin is achieved in a series f steps, rather than ne step, the enthalpy change fr the verall reactin is equal t the sum f the enthalpy changes fr each step in the reactin series Pst-lab calculatins Mass f slutin: assume density is the same as that f water (if nt explicitly stated), then cnvert straight frm vlume t mass Mass f Reactants (slid and liquid): add mass f slid t calculated mass f liquid Change in Temperature: T(final) T(initial) Heat (see page 5- calrimetry) Mles f slid reactant: mlar mass Enthalpy change: q/mles Average Enthalpy change: average the trials 5.6 (DON T) TASTE THE RAINBOW [AFTER AP EXAM] Pre-Lab Calculatins Mlarity f diluted vinegar: M 1V 1=M 2V 2 Mlarity f husehld vinegar: same as dilute Percent by mass: (mlarity (ml/l) milliliters mlar mass density)*100 Shuld end with all units canceling 5.7 MW BY FPD [AFTER AP EXAM] Freezing Pint Lab Effect f Unknwn n Lauric Acid Freezing Pint Little bit f unknwn = little lwer Mre unknwn = even lwer Page 9 f 10
5.8 SPEED OF A REACTION [AFTER AP EXAM] Reactin Order Graphs Pre-Lab Infrmatin Sensr used t measure cncentratin f clr ver time: clrimeter Knw hw t d all f the calculatins in a graphing calculatr 5.9 QUALITATIVE CATION LAB [AFTER AP EXAM] Washing Precipitates Why? Remve free flating ins frm the precipitate Hw 1-2 ml f distilled water (unless anther chemical is specified) Stir Centrifuge (15-20 secnds) Discard wash water (but be careful t nt drain the precipitate until tld t d s in lab instructins) My Tips Keep track f which slutin is in which beaker (labels in pencil are extremely helpful) Knw what exactly yu are lking fr when testing the unknwn: use the prcedure in additin t detailed ntes taken thrughut the initial experiment The results frm testing the unknwn may nt exactly match yur experiment but as lng as they fit in with the prcedural descriptins yu shuld be gd t g DON T SECOND GUESS YOURSELF!!! If yu are sure yu saw a precipitate then there is smething there, even if it lks a little funky, in that case (if yu have time) red the trial just in case NOTES! Taking detailed ntes n bservatins thrughut the experiment is very helpful, be it n an extra sheet f paper r directly n the lab, they will help yu figure ut if the in really is there DON T SKIP STEPS! Yes, yu have t make sure is silver, n ne cares if yu are psitive that it s silver if yu haven t cnducted an experiment that cnfirms that it is in fact silver. Dn t rush! Take yur time and be extra careful, this is after all the final exam. GOOD LUCK!! MAY THE RESULTS OF THE LABS BE EVER IN YOUR FAVOR! AND MAY THE FORCE BE WITH YOU! Page 10 f 10