Teaching High School Chemistry Cheat Sheet

0 1 : I n t r o d u ct i o n t o H ig h Sch o o l Ch em i st r y W h a t c o n t en t ar e t e a ch e r s co v e r i n g ? 571 high school t eachers were survey ed on what chem ist r y t opics wer e appropriate t o t each. 96% of t he t eachers ranked t hese t opics as appropriate. 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. Basic laboratory sk ills. Basic skills Dim ensional analysis Classificat ion of m at t er . Writing and nam ing form ulas. Moles Types of react ions. Balancing equat ions St oichiom et r y At om ic st ruct ure ( elect ron configurat ion) Periodic t able & periodicity Types of bonds and pr opert ies. Gas laws Solutions and concent rations Ap p l y i n g co n t e n t t o st u d e n t s’ l i v es Applicat ion of cont ent increases m ot ivat ion and int er est, which in turn increases per form ance. Text books t hat hav e t rue int egrat ion of application and int roduce topics on a need- t o- k now basis.  Chem ist ry I n the Com m unit y ( Chem Com ) htt p: / / www .w hfreem an.com / chem com / • Living by Chem ist ry htt p: / / ww w. keypress.com / chem ist ry /  Act ive Chem ist r y ht t p: / / ww w.its- about tim e.com / ht m ls/ ac/ ac.ht m l  Chem ist ry in Your Wor ld  www .RealLifeChem ist r y.net I deas for research pr oj ect s and present at ions apply ing chem ist ry t o st udent s’ lives:  Fuel- cell cars  Hair dyes  Fireworks • Lum inol  Glow in t he dark algae.  Nuclear power plant .  Or anyt hing else im aginable. Art icles with applicat ion:  New spaper s  Chem ical & Engineer ing New s  Chem Mat ter s 0 2 : Te ach in g La b s i n Ch em is t r y Lab Saf e t y • Wear splash- proof goggles. • No eating or dr inking. • Do not t ouch, t ast e or direct ly sm ell chem icals. • Tie back all loose clot hing, hair and j ewelry. • Alw ays read t he pr ocedure ahead of t im e and follow it closely. • Nev er r etur n unused chem icals t o t he original cont ainer. • Dispose of all chem icals as inst r uct ed. • Alw ays report all incident s ( spills, breakage, m ist akes in perform ing a pr ocedur e) t o y our inst ruct or ! Ru n n i n g a La b • Alw ays include writ ten safety inform at ion and go over it verbally. • Go over any new t echniques or equipm ent ahead of t im e • Walk around and keep an eye on everyt hing! • Refill chem ical supply when needed—but not t oo m uch t o keep waste dow n. • Ask st udent s quest ions to engage them with t he pr ocedure. • Ant icipat e quest ions—if you see one gr oup having a quest ion or problem , ot her s w ill as w ell! 0 3 : A ssessm e n t s i n Ch em i st r y • Lo n g a n s w er : Assesses crit ical think ing and application of knowledge. Essay, shor t answ er essay and calculat ions problem s. • Sh o r t a n s w er : Assess knowledge of fact s. True/ false, m at ching, fill in t he blank and m ult iple choice. W a y s t o in c r e a se d i f f i cu l t y o f sh o r t an s w er • M u lt i p le - ch o i ce : Require cor rect wor k shown on quant it at iv e quest ions t o elim inat e aw arding point s for correct guessing. • M at c h in g : Have m ore opt ions t han quest ions so they cannot apply “ process of elim ination” on t he last few . • Tr u e/ Fa l s e: Have them correct false st at em ent s, or explain why t hey’r e false • Fi l l i n t h e b a n k : Don’t prov ide a word bank. 0 4 : M ea su r em en t & Ma t h in Ch em i st r y The m e t r ic s y st em uses pr efix es t o indicat e m ultiples of 10. Me t r i c Pr e f i x es co m m o n l y u s ed i n ch e m ist r y Pr ef i x Sy m b o l Mu lt ip l e Kilo k 1000 Deci d 0.1 Cent i c 0.01 Milli m 0.001 Micro μ 0.000001 Nano n 0.000000001 The “ base unit ” is when t here’s no prefix. The SI sy t em gives t he fundam ent al unit for each t ype of m easurem ent . Co u n t in g Si g n i f i ca n t Fi g u r es : • I f t here is a decim al point anyw here in t he num ber: St art wit h t he first non- zero num ber and count all digit s unt il t he end. • I f t here is not a decim al point in the num ber : St ar t with t he first non- zero num ber and count unt il t he last non- zero num ber. Cal cu l at i o n s w i t h si g n i f i ca n t f i g u r es : • Alw ays com plet e calculat ions before rounding. • Adding/ subtr act ing: Answer has least num ber of decim al places as t he problem . • Mult iply ing/ div iding: Answer has least num ber of significant figur es in pr oblem . Sci e n t if i c N o t a t io n —a short hand m et hod of writing num bers using power s of 10. W r i t i n g s ci e n t i f i c n o t a t io n : 1. The decim al point is alw ay s m oved to after t he 1 st nonzer o num ber . 2. Count t he num ber of t im es t he decim al point is m oved and use t his as t he power of 10. 3. “ Big” num bers (> 1) hav e positive exponent s. “ Sm all” num bers (< 1) have negat ive exponent s. Re a d i n g sci en t i f i c n o t a t io n : 1. Power of 10 = num ber of t im es t o m ov e decim al point 2. Posit iv e power s = m ake t he num ber “ Big” ( > 1) . Negat ive exponent s = m ak e the num ber “ Sm all” ( < 1) . Lo g a r i t h m s: Way of count ing in m ult iples of the base x = logb y Cal cu l at o r t ip s : • Alw ays use the ÷ key t o designat e a num ber is on t he bot t om of an expression. • Alw ays use t he EE ( or EXP) key t o ent er scient ific notat ion. • Alw ays use parent hesis around addition or subt ract ion when com bining it with ot her oper at ions. • To m ake som et hing negat ive ( w hen tak ing t he num ber t o a power) , k eep the negat ive outside of t he par ent hesis. 0 5 : D i m en s io n a l An a ly si s O7 : En er g y & M at t er Di m en si o n al a n a l y si s is t he t echnique used t o conver t units. Pu r e Su b s t a n ce Elem ent Com pound Hy drogen H2O Th e p r in c i p le b eh i n d d im en si o n a l an a l y s i s: Mult iplying by 1 does not change t he physical m eaning of t he m easurem ent . Usi n g Di m en si o n al A n a l y si s : 1. Write your given inform at ion on t he left side. 2. Write “ = ______ ( desired unit) ” on t he right side. 3. Find equalities t hat include both t he desired unit and t he given unit. 4. Arr ange t he equalities so t hat t he given unit cancels. 5. Calculate answer , m ult iply acr oss t he t op and div ide acr oss bot t om . Mu l t i - st ep D i m e n si o n al A n a l y si s • I f t here is no equalit y t hat cont ains bot h the given and the desir ed unit, y ou will need to use m ore t han one equalit y . • I f you convert from a m et ric prefix t o another m et r ic pr efix , use t he base unit as a bridge in- bet w een. W h e n co n v e r t i n g a q u an t i t y w i t h a f r a ct i o n a l u n i t : Separat e t he unit —put t he top on t he t op of the ex pr ession and t he bot t om of the unit on t he bot t om of t he expression. 0 6 : So lv i n g Ch em i st r y Pr o b l em s Use t h e K U D OS m et h o d f o r so lv i n g w or d p r o b l em s. K = Known U = Unknown D = Definit ion O = Out put S = Subst antiat ion Kinet ic Ener gy ( KE) Ener gy due t o m ot ion • D ( De f i n i t i o n ) : Find equalities t o conver t . Choose and rear range equations. Look for m issing infor m at ion in ot her places. I f you cannot find enough infor m at ion, r e- evaluat e your plan. • O ( Ou t p u t ) : Plug in values t o t he equations, use const ant s as needed. Check unit cancellat ion and per for m t he calculation. • S ( Su b st a n t ia t i o n ) : Check validit y of your answ er . Check unit s and significant figur es. M i x t u r es Hom ogeneous Heter ogeneous Tap wat er Sand & Wat er En e r g y Pot ent ial Energy ( PE) St ored in chem ical bonds Ph y s i ca l Ch a n g e s • Do not cr eat e a new subst ance. • All changes in st ate ( bet ween solids, liquids and gases) ar e phy sical changes. Breaking, cut t ing, dissolving, dry ing, m elting, freezing, et c. Ch em ica l Ch a n g e s • Do produce new subst ances. So m e s i g n s o f a ch em ica l ch an g e a r e : • Product ion of a gas ( bubbles) • Heat change, get t ing hot or cold. • Light • Change in color. • Form ation of a pr ecipit at e ( form ing an insoluble subst ance from two soluble subst ances. • However, som e of t hese signs could be present in phy sical changes as well. • Rust ing, burning, react ing w ith water , react ing wit h acid, etc. 0 8 : Pu r e Su b st a n ce s—A t o m s & Mo l e cu l es Su b - a t o m i c Pa r t i cl e s: Pa r t i cl e Lo ca t i o n Prot on Nucleus • K ( K n o w n ) : Use unit s t o indent ify inform at ion, Writ e inform at ion sym bolically, Look for im plied infor m at ion, Write out chem ical equat ions. • U ( Un k n o w n ) : What is t he problem looking for ? Writ e inform at ion sym bolically. M a t t er Neut r on Nucleus Elect ron Outside the nucleus M a ss 1 am u = 1.67 × 10 - 2 7 kg 1 am u = 1.67 × 10 - 2 7 kg 0.00055 am u = 9.10 × 10 - 3 1 kg Ch a r g e +1 0 -1 I on s • At om s can gain or lose elect r ons to for m i o n s ( at om s wit h a char ge. • An i o n : Atom wit h a negat ive char ge. • Cat i on : At om w it h a posit ive char ge. El e m en t sy m b o l s: A Z • • • • A= Z= C= # = X #C Where m ass num ber ( # of protons + # of neut rons) atom ic num ber ( # of prot ons) char ge ( # of protons - # of elect rons) num ber of at om s I so t o p es: At om s of sam e elem ent w it h differ ent num ber of neutr ons ( and differ ent m ass) . • Mass num ber refers only t o a specific isot ope. Ca l cu l a t i n g a v er ag e a t o m ic m a ss : Found on per iodic t able. At om ic m ass = Σ( fractional abundance) (m ass of t hat isotope) . At o m s, e l e m en t s an d m o l ec u l e s • At o m s : Made of sub- at om ic part icles. • El e m en t s: Made of the sam e t ype of at om ( each has t he sam e num ber of protons) . • M o l e cu l e s : Made of m ore t han one t ype of at om ( m ore t han one elem ent ) chem ically bonded t oget her. 0 9 : W r i t in g Ch e m ica l Fo r m u l a s 1 0 : Co u n t i n g M o l ecu le s—Th e M o l e Ty p e 1 Bi n ar y i o n i c: Contains tw o elem ent s—one m etal and one non- m et al. 1. Write t he sym bol and charge of the first elem ent . 2. Write t he sym bol and charge of the second elem ent . 3. Balance t he charges t o form a neut r al com pound by using subscript s. M o l e : SI unit for count ing ( abbreviation: m ol) • 1 m ole of any t hing = 6.02 × 10 23 pieces. • The atom ic m ass found on t he per iodic t able is the m ass ( in gr am s) for 1 m ole of at om s of that elem ent . • At standard t em perat ure and pr essure ( STP) , 1 m ole of any gas is 22.4 L ( Mo l a r Vo l u m e o f a g as ) Ty p e 1 o r 2 w i t h M u lt i v al en t M e t a l s Me t al s t h a t ca n h av e m o r e t h a n o n e ch a r g e . 1. The Rom an num eral indicat es the char ge of t he cat ion m et al. 2. Follow the r ules for Type # 1 or Type # 2 as it applies. M o l a r M a ss ( M o l ecu l a r M a ss , Fo r m u l a W e i g h t ) : • By adding t he at om m asses for at om s in a m olecule, t he m olar m ass of t he m olecule can be found. • Be sure t o dist ribut e subscript s out side t he par ent hesis t o each at om inside. Ty p e 3 Bi n ar y Co v a l e n t : Cont ains t wo non- m etals ( w hich do not for m charges w hen bonding t oget her ) . 1. Do not worry about charges wit h t his t ype. 2. Write t he first elem ent ’s sym bol. 3. Write t he second elem ent ’s sy m bol. 4. Use t he prefixes t o deter m ine subscript s ( “ m ono” is not used on t he first elem ent ) . Pe r c en t Co m p o si t i o n : Ac i d s: 1. “ Acid” indicat es “ H + ” is t he cat ion. 2. Choose t he anion: a. “ hydro__ic acid” – anion is single elem ent ( no oxy gen). b. “ __ic acid” – anion is “ __ate” ion c. “ __ous acid” – anion is “ __it e” ion 3. Balance charges w it h subscript s. 1 0 : N a m in g Ch e m ica ls Ty p e 1 Bi n ar y i o n i c: Contains t wo elem ent s—one m etal & one non- m et al. 1. Write t he nam e of t he fir st elem ent . 2. Write t he nam e of t he second elem ent with “ - ide” ( subscript s do not m at t er in t his t ype) . Ty p e 2 Po l y a t o m i c I o n i c: Cont ains at least one p o l y at o m i c i o n ( group of at om s t hat t oget her have a charge) . 1. Write t he nam e of the m et al or “ am m onium ” for NH4 . 2. Write t he nam e of the poly at om ic anion ( do not change t he ending) or t he single elem ent w it h “ - ide” . Subscript s w it hin a polyat om ic ion m ust m at ch t he nam e exact ly. I f t her e are parent hesis, the polyat om ic ion is inside t he parent hesis. Ty p e 1 o r 2 w i t h M u lt i v al en t M e t a l s Met als t hat can have m ore than one charge. Co, Cr, Cu, Fe, Hg, Pb, Sn 1. Nam e t he cation and anion as for Type # 1 or Type # 2. 2. The com pound is neut ral. Use t he char ge of t he anion to det erm ine t he charge of the cat ion. 3. Write t he charge of t he cation in Rom an num erals inside parent hesis. Ty p e 3 Bi n ar y Co v a l e n t : Cont ains t wo non- m etals ( w hich do not for m charges w hen bonding t oget her ) . 1. 2. Write t he first elem ent ’s nam e w it h t he prefix indicat ing t he # of m olecules ( m ono- is not used with t he first elem ent ) . Write t he second elem ent ’s nam e w it h the prefix indicating t he # of m olecules and “ - ide” . Ac i d s: ( Com pounds with “ H + ” cations ar e acids) 1. Look up t he anion: a. No ox ygen, a single elem ent : “ hy dro__ic acid” b. “ __at e” ion: “ __ic acid” c. “ __it e” ion: “ __ous acid” % compositio n = mass element × 100 mass whole I f a chem ical form ula is giv en, use at om ic m asses and m olar m ass in % com posit ion. Em p ir ica l f o r m u l a ( lowest rat io of at om s in m olecule) : 1. I f given percent’s, assum e they ar e gr am s. Change all gr am s t o m oles. 2. Div ide all m oles by the sm allest to get t he lowest rat io. Mult iply by a fact or if needed t o m ake whole num bers. 3. Write t he form ula w it h t he rat io as subscript s. M o l e cu l a r Fo r m u l a ( act ual r at io of at om s in a m olecule) : 1. Find em pirical form ula, if not given t o you. 2. Find t he m olar m ass of t he em pirical form ula. 3. Find t he rat io of t he m olecular form ula’s m olar m ass ( given t o you) t o the em pirical form ula’s m olar m ass. 4. Mult iple t he em pirical form ula’s subscr ipt s by t he rat io. 1 2 : Ch e m ica l Rea ct i o n s Ch em ica l Rea ct i o n : Bonds and at om s ar e rear ranged to form new com pounds. Ch em ica l Eq u a t io n : Sy m bolizes the chem ical react ion w it h chem ical for m ulas. • React ant s Æ Pr oduct s • St at es of m at t er ar e show n ( s = solid, l = liquid, g = gas, aq = aqueous) . • Coefficient s give m ole r at io. • A double arrow ( ') indicat es it is a rever sible reaction also known as an equilibr ium r eact ion. Ty p e s o f r e a c t i o n s: • Co m p os i t i o n : More t han one t ype of m at t er com bine t o form one ty pe of m at ter . • De co m p o si t i o n : One t ype of m att er decom poses int o m or e t han one type of m at t er. • Si n g l e r e p l a ce m e n t : A single elem ent changes place wit h an ion in a com pound. • Do u b l e r ep l a c em en t : Two ionic com pounds sw it ch ions. • N e u t r a l i za t io n r ea ct io n : Double replacem ent r eact ion wit h an acid and a base as the r eactants. • Re d o x r e a ct io n : Reduction- oxidat ion react ion. • Pr eci p i t at i o n r e act i o n : A precipit at e is form ed. So l u b i l i t y r u l es f o r d e t er m in i n g p r e ci p i t at es : An i o n Fo r m s in s o l u b l e co m p o u n d s w it h NO 3 No com m on ions CH3 COO Ag + Cl- , Br - , I Ag + , Pb 2+ , Hg 2 2+ , Ti + SO4 2 Ag + , Pb 2+ , Ba 2+ , Sr 2 + , Ca 2+ CrO4 2Ag + , Pb 2 + , Ba 2+ , Sr 2+ 2S All anions ex cept NH4+ , colum ns 1 & 2 OH All anions ex cept NH 4 + , colum n 1, Ba 2+ & Sr 2 + CO3 2- , PO4 3- All anions ex cept NH 4 + , colum n 1 ( ex cept Li + ) NH 4 + , Na + and K+ are soluble w it h all com m on ions 1 3 : Ba l an ci n g Eq u a t i o n s Zn + H + → Zn 2 + + H 2 React ant s 1 1 +1 Zn H Char ge + 1 2 +2 Product s 2+ __ Zn + _2_ H Æ __ Zn + __ H 2 React ant s Zn 1 H 1 2 Char ge +1 2 1 2 +2 Product s 1 Zn + 2 H + → 1 Zn 2 + + 1 H 2 1 4 : St o i ch io m e t r y St o i ch i o m e t r y : Using the m ole ratio in the balanced equation and inform at ion about one com pound t o find inform at ion about anot her in t he r eaction. Eq u a l i t ie s u se d d u r in g d i m e n si o n a l an a l y si s f o r st o i ch i o m e t r y : • Mo l e r a t i o i n b a l a n ce d e q u at i o n : Used t o conver t betw een m oles of differ ent com pounds in t he balanced equation. • Mo l a r m a s s: Used to conv ert bet ween gram s and m oles. • Co n cen t r at i o n : Used to conv ert betw een m oles and lit ers of a solut ion. Molarity = moles solute L solution • Mo l a r v o l u m e o f a g a s: Used t o conver t betw een m oles and lit ers of a gas at STP. M as s- M a ss ex a m p l e : I f 2.5 g Mg react , how m any gram s MgCl 2 are pr oduced? 2.5 g Mg 1 m ole 1 m ole 95.21 g MgCl2 Mg MgCl2 = 9.8 g MgCl 2 1 m ole 1 m ole 24.31 g Mg Mg MgCl2 Li m i t i n g r ea ct an t : React ant t hat st ops t he react ion by running out fir st . • Once a react ant has run out, t he r eact ion w ill st op. • Do st oichiom et r y for each given reactant quant it y t o t he sam e product each tim e. Choose the calculat ion that giv es the sm allest am ount of pr oduct . • The react ant t hat produces t he sm allest am ount of pr oduct is t he lim it ing react ant . Pe r c en t y i el d : com pares t he act ual yield to the t heor et ical yield. % yield = actual yield × 100 theoretical yield 1 5 : El e ct r o n Co n f i g u r a t i o n El e ct r o n cl o u d : Area out side nucleus where elect r ons ar e locat ed. En e r g y l ev e l s: Elect r on cloud is divided int o ener gy levels for elect rons. Su b sh el ls : Energy levels of elect rons are divided int o subshells of equal energy or bit als. Or b i t a l s: Subdivision of a subshell. Each orbital can hold 2 elect rons. 4 t y p e s o f su b sh e l l s: Su b s h e l l Be g in s i n le v e l s 1 p 2 d 3 f 4 ← higher energy • The Law of Conser vat ion of Mass/ Mat t er requires t hat a chem ical react ion be balanced. • Coefficient s balance at om s in a chem ical r eact ion and indicat e t he nu m ber of com pounds in a react ion. I n sp ect i o n M et h o d ( t o balance t he m ost sim ple react ions) : 1. Make a list of t he elem ent s in t he react ion. 2. Count t he # of each t ype of at om on each side. 3. Add coefficient s t o balance t he num ber of at om s. 4. Det er m ine the t ot al charge of each side and use coefficien t s t o balance char ge. 5. When elem ents and char ge are balanced, place a “ 1” in any em pt y coefficient location. # of o r b i t al s 1 3 5 7 # of el ect r o n s 2 6 10 14 Au f b au Pr in ci p l e: Fill shells fr om lowest energy to highest . H u n d ’ s Ru l e : Elect rons are placed in each equal- ener gy orbit al before doubling up to pr oduce t he low est energy at om . Pa u l i Ex cl u s i o n Pr i n ci p l e: Two elect rons occupying the sam e orbit al m ust have opposite spins ( angular m om ent um ) . Use t h e p e r io d i c t a b le a s a g u i d e ( r e a d le f t t o r i g h t ) : 1s 2s 2p 3s 3p 4s 3d 4p 5s 4d 5p 6s 4f 5d 6p 7s 5f 6d 7p 3 t y p e s o f e l e ct r o n co n f i g u r a t i o n n o t a t i o n : Bo x es & Ar r o w s: O ( 8 elect r ons) : 1s ↑↓ 2s ↑↓ 2p ↑↓ ↑ Sp e c t r o sco pi c: Br (35 elect r ons) : 1s2 2s2 2p 6 3s2 3p 6 4s2 3d 10 4p 5 N o b l e Gas : Br (35 elect r ons) : [ Ar] 4s2 3d 1 0 4p 5 ↑ 1 6 : Th e Per i o d i c Ta b l e Pe r i o d i c Ta b l e : Tool for or ganizing the elem ent s. Pe r i o d s: Rows on t he per iodic t able. Gr o u p s: Colum ns on the periodic t able. Pe r i o d ici t y : Predict able pat t er ns and trends on the periodic t able. Gen e r a l t r en d s i n t h e p e r i o d t a b le Tr en d Æ a p er io d At om ic Mass I ncreases At om ic Radii Decreases I onization energy I ncreases Elect r on Affinit y I ncreases Elect r onegat iv ity I ncreases ↓ a g r ou p I ncreases I ncreases Decreases Decreases Decreases Ra d i i w h e n f o r m i n g a ca t i o n : There ar e now m ore prot ons t han electr ons. The pull of t he prot ons on each electr on is gr eat er . Cat ions have sm aller radii t han t heir parent at om . Ra d i i w h e n f o r m i n g a n an io n : There are fewer pr ot ons t han electr ons. The pull of t he prot ons on each electr on is less. Anions have larger radii t han t heir parent at om . Bo n d t y p e 1 9 : Ga s La w s 1 7 : Ch e m ica l B o n d i n g H ap p e n s b e t w een Met al & non- m et al Non- m et als Non-m et als El e ct r o n s ar e I onic Transfer red Cov alent Shared Polar Shar ed Cov alent unev enly Met allic Met als pooled Po l a r co v a l e n t b o n d When nonm et als bond cov alent ly with a lar ge differ ence in elect ronegat ivity. • Absolut e value of differ ences: d. 0 – 0.4 = covalent e. 0.5 – 1.4 = polar covalent f. 1.5 – 4 = ionic Si g m a ( σ) b o n d : First bond bet w een t wo atom s form ed from head on overlap of or bit als Pi ( π) b o n d : bond bet w een t wo atom s form ed from ov erlap of par allel p orbit als. As su m p t i o n s o f t h e KM T 1. Gases are m ade of atom s or m olecules. 2. Gas part icles ar e in rapid, random , const ant m ot ion. 3. The tem perat ur e is proport ional to the aver age kinet ic energy. 4. Gas part icles are not att ract ed nor repelled from each ot her 5. All gas par t icle collisions are perfect ly elast ic ( t hey leav e wit h t he sam e ener gy they collided wit h) . 6. The volum e of gas part icles is so sm all com pared to the space bet w een t hem , t hat t he volum e of t he part icle is insignificant. Sy m b o l s f o r a l l g as Law s: P = Pressur e; V = Volum e; n = m oles; T = Tem perat ure ( in Kelvin: K = °C + 273) ; R = Gas const ant ( 8.31 L kPa/ m ole K or 0.0821 L at m / m ole K) ; “ a” and “ b” = correct ion fact or s for real gases. Co m b i n ed Ga s La w : Each single bond is a sigm a bond. Each double or t riple bond cont ains one sigm a bond and t hen pi bonds to form t he second or third bond. Ex a m p l e : How m any sigm a and pi bonds ar e in t he following? H H | | H–C= C– C≡C Da l t o n ’ s Law o f Par t i a l Pr es su r e : χA = M o l e f r a ct i o n : Va l e n ce Sh e l l : Elect rons in t he outer m ost shell t hat bond. Oct e t Ru l e: At om s ar e m ost stable when having a full valence shell. Ar r an g i n g A t o m s in Lew i s St r u c t u r es 1. Wit h only 2 elem ent s, arr ange sy m m et rically. 2. “ COOH” is a car boxylic acid. Both O’s bond t o t he C and t he H goes on one of the O’s. 3. Hy drogen and halogens cannot go in t he m iddle. 4. Ot her at om s in the or der t hey appear in t he form ula 5. Hy drogen and halogen atom s go around the elem ent t hey are wr it t en next t o in t he for m ula. Lew i s St r u ct u r e : A 2D representation of a m olecule and its bonds. 1. Arr ange t he at om s as abov e. 2. Det er m ine the # of valence elect rons for each atom . 3. Draw t he valence elect rons—do not double up w here a bond is going to form bet w een t wo at om s. 4. Count t o see if all atom s have full valences. 5. I f t wo atom s adj acent t o each ot her do not have full valences, m ove in an elect ron from each to form a double bond. Repeat for tr iple bond if necessar y. Mov e hydr ogens as needed t o allow double/ t riple bonds. Ex c ep t io n s t o t h e Oct e t Ru l e : 1. Hy drogen and Helium can only hold 2 elect rons Bor on and Bery llium can be full wit h 6 elect rons. 2. Any elem ent in period 3 or below can have m ore t han 8 elect rons. Va l e n ce Sh el l El e ct r o n Pa i r Re p u l s i o n Th e o r y ( V SEPR) : Bonds and lone pairs ( elect rons) r epel and ar range t hem selv es in 3D as far aw ay from each ot her as possible. Ptotal = ∑ Pof each gas mole A mole total Pa r t i a l Pr ess u r e an d m o l e f r a ct i o n : 6 sigm a bonds & 3 pi bonds 1 8 : M o l ecu l ar St r u ct u r es P1V1 P2V2 = n1T1 n 2T 2 I d e a l Gas La w : Re a l Gas Law : PA = χ A Ptotal PV = nRT 2 ⎛ n a⎞ ⎜⎜ P + V 2 ⎟⎟(V − nb ) = nRT ⎝ ⎠ 2 0 : So l u t i o n s So l u t i o n : Hom ogeneous m ixt ure. So l u t e: Subst ance being dissolved. So l v en t : Subst ance doing the dissolving. Fa ct or s af f ect i n g So l u b il it y : • Pr ess u r e : Gases: as Pressure increases, solubilit y increases • Tem p e r a t u r e: Gases: higher t em perat ure is low er solubility. Most solids: higher t em per at ure is higher solubilit y . Co n ce n t r a t i o n M ea su r e m en t s: % b y m a ss : % mass = mass solute ×100 mass solution Mo l a r i t y ( M ) : Molarity = moles solute L solution M o l a l i t y ( m ) : Molality = moles solute kg solvent Di l u t i o n e q u a t i o n : M 1V1 = M 2V2 El e ct r o l y t e: Com pounds dissociat e int o ions when dissolved in wat er. This allow s t he solut ion t o conduct elect r icit y . 2 1 : Re act i o n Rat es & Eq u il i b r i u m Ki n et i cs: The st udy of react ion r at es. I n o r d er f o r a r ea ct i o n t o o cc u r , t h e m o le cu le s m u st : Collide with t he correct orientation and act ivat ion ener gy . Act i v at i o n En er g y is t he m inim um energy needed for a react ion t o occur. Fa ct o r s a f f e ct in g r a t e: • Su r f ac e a r e a —As surface ar ea increases, rat e increases. • Co n ce n t r a t i on —As concent ration increases, rat e incr eases. • Tem p e r a t u r e—As tem perat ure increases, rat e increases. • Cat a l y st —Pr esence of a catalyst increases rat e. Re v er si b l e Re act i o n : React ion that goes in both direct ions. Eq u i l i b r i u m : When t he rat e of t he for war d and rev erse of a rever sible process ar e equal. Dy n a m i c eq u i l i b r i u m : The num ber of react ant s and pr oduct s do not change, but t he react ion continues t o occur in both dir ect ions. 2 3 : Th e r m o d y n a m i cs Th er m o d y n a m i cs : St udy of heat changes. En e r g y : The ability t o do work or supply heat . He a t ( q ) : Flow of energy from a hot t er obj ect t o a cooler obj ect . En t h al p y ( H) : Tak es int o account int er nal energy, pressur e and v olum e. Sam e as heat for open-air sit uat ions. Cal o r i m et r y : ΔH syst em = ΔH sur roun dings T2 of bot h syst em and surr oundings are t he sam e Work w = − PΔV w = work ( in J) ; P = pressure ( in atm ) ; ΔV = V 2 – V 1 ( in L) Fo r ch a n g es i n t em p er a t u r e : ΔH = m ×C p × Δ T m = m ass ΔT = T2 – T1 Fo r ch a n g es in st a t e: Tem perat ur e doesn’t change as t he added energy is used to break int erm olecular forces. Melt ing: ΔH = m × H fus Hfu s = ent halpy of fusion Boiling: ΔH = m × H vap W r it i n g Eq u il i b r iu m Co n s t a n t Ex p r e ssi o n s • Concent rat ion of pr oduct s over concent rat ion of react ant s. • Do not include pur e solids or pure liquids. • Use t he coefficient s of the balanced equat ions as powers. Hvap = ent halpy of vaporizat ion ( freezing and condensing use the opposit e values— exother m ic) En t h al p y o f f o r m at i o n ( H f ) : Ener gy change when a com pound is form ed fr om it s elem ent s. Re a ct io n Qu o t i en t ( Q) : When concent rat ions at any tim e are plugged int o t he equilibrium constant expression. • I f Q = K, it ’s at equilibrium . • I f Q > K, react ion proceeds t ow ards react ant s. • I f Q < K, r eaction pr oceeds t owards pr oduct s. En t r o p y ( S) : Disorder or random - ness Fr e e En e r g y ( G) : Tak es into account ent halpy, ent ropy and t em perature t o det er m ine spontaneity Le Ch a t el i e r ’ s Pr i n c i p le : A sy st em at equilibrium will readjust t o reach equilibrium again when dist urbed. - ΔG = Spontaneous at t hat t em perat ure. + ΔG = Spont aneou s in t he opposite direct ion at t hat t em peratur e. 2 2 : A ci d s a n d Ba se s Ar r h en i u s aci d : Produces hy dronium ion in w at er. Ar r eh n i u s b a s e: Produces hydrox ide ion in wat er . Hy d r o n i u m i o n : H3 O+ 1 ; H y d r o x i d e i o n : OH - 1 St r o n g a ci d s St r o n g b a se s HCl, HBr , HI , HNO3 , HClO3 , HClO4 NaOH, KOH, Ca( OH) 2 , Ba(OH) 2 , Sr( OH) 2 Po l y p r o t ic a ci d s : each successive pr ot on is w eak er t han t he one before. ( H 2 SO 4 has a st r ong 1 st hy drogen) . p H : Logarit hm ic scale of acidity. 1 pH = −log[ H 3 O + ] [ H 3 O +1 ] = 10 − pH 1 1 K w = [ H 3O + ][OH − ] at 25° C, Kw = 1.0×10 -1 4 Sal t f r o m • Weak acid + st r ong base = Basic • St rong acid + w eak base = Acidic Bu f f e r : Weak acid or base and it s conjugat e t hat resist s changes in pH when acid or bases is added. ΔHrxn = ∑ H f prod − ∑ H f react ΔG = ΔH − T ΔS 2 4 : Ele ct r o ch e m ist r y El e ct r o ch e m i st r y : The st udy of the int er - change bet ween elect rical and chem ical energy . Vo l t a i c ce l l ( o r Ga l v a n i c ce l l ) : Uses a redox react ion to pr oduce elect ricity. El e ct r o m o t i v e f o r ce , EM F ( o r Cel l Po t e n t ia l ) : Difference of poten tial energy of elect r ons fr om before and aft er the t ransfer. St a n d a r d r ed u ct i o n p o t en t i al : EMF if hydrogen is used as t he ot her half- react ion ( Hydrogen is defined as “ 0” ) . Ca l cu l a t in g EM F f r o m st an d a r d r ed u ct io n p o t e n t i a ls : EMF = cathode – anode + EMF = spont aneous St o i ch i o m et r y & El e ct r o c h e m i s t r y : 1 am p ( A) = 1 Coulom b/ sec ( C/ s) 1 Far aday ( F) = 1 m ole of e - 1 1 Far aday ( 1 m ole of e - 1 ) = 96475 Coulom b ( C) Ox i d a t i o n n u m be r r u l e s: • The sum of all oxidat ion num bers m ust equal t he ov erall charge of t he species. 0 for elem ent s or com pounds, t he char ge for a polyatom ic ion. • Hy drogen is + 1 when wit h nonm et als, - 1 w it h m et als. • Oxygen is usually - 2. • Halogens ( colum n 7) ar e usually - 1. • The oxidat ion num ber of an ion in an ionic com pound is t he char ge. Fo r r e d o x r e a ct i o n s t h a t ca n n o t b e b al a n ced w it h i n sp ec t i o n m et h o d : • Det er m ine the ox idat ion num ber s of each at om . • Det er m ine t he net change in charge. Use t he net change t o det er m ine t he rat io of atom s t hat would cancel out t he net charge change. • Use t he ratio as coefficient s in the sim plest com pounds cont aining those elem ent s. • Finish balancing by the inspect ion m et hod.