1.1 Notes - Reaction Kinetics

Transcription

1 Chemistry 12-Unit I-Reaction Kinetics=Notes Chemistry Notes - Reaction Kinetics Reaction Kinetics is the study of rates and the factors which affect the rates. Expressing Rates rate = ~guantity of a product formed f:l time or rate = _~guantity of a reactant consumed ~time in general: rate = ~ amount (a reactant or product) ~time Note: A time unit is always in the denominator ~ '- ~i(\.) S.l hr J cl~. of a rate equation. If you have... Il Amount can be measured Units: as: Solids (s) ~mass grams (g) Gases (g) ~ volume Litres (L) ~ pressure Atmospheres (atm) ~ mass (if open container) grams (g) Aqueous ions (aq) ~ molarity ~C\Of'"1 Molarity (M) or mol/l Any species can be measured in ~ moles/ ~ time Note: We don't measure the concentrations (~ molarity) of pure liquids (ex: H 2 0) and solids since they have constant densities (basically constant concentrations). Chemistry 12-Unit l-reaction Kinetics-Notes Page 1 of 17pages

2 Chemistry J2-Unit J-Reaction Kinetics--Notes eg.) How could we measure the rate of this reaction: Z11(s)+ 2HCI(aq) ~ H2(g) + ZnCI2(aq) r = Ll mass ofzn r = Ll [HCI] (note:[] = molarconcentration) fo. ~: -t"\ s r = Ll mass of container (as H2 (g) escapes) r = Ll volume H2 Spectator Ions - some rxs, when written in ionic form show that some ions don't change concentration. Ions that appear on both sides of the arrow in equal amounts are called SPE:cTWfo C'4 ions! ego Mg(s) + 2HC~ ~ H2(g) + MgCI@ NOTE: To writean equationin IONIC FORM, dissociateall the aqueous(aq)compounds: br--:tz C4 ~ " (1 t7> ita u + "..)~, I )..-f J DrV,s,v~~:)fo:m 2 IJ ~) -+ 2~) -7 H1.. t{j) + M(j ta.j) + 2. G~) (use ion chart) *j1>j.vpt~ Oc:Ulittbll S~ ChlU~S Of rons" Write 4 possible equations which express rate for this reaction: (i) ra-\l =p 'ri\ d ~ ~.,+ ~ ~.@ ~J,L -=- A C M,9 2-~J f:j t\ V'A.e.., Is tim-<"" ~ ~te- -;:.~ 1'1\a~~ 0+ cpt\+ai nly I to~nh' ~ b t\~ l0rn-k=- ~ \JO\u.w'\{ ()~ \-h Lv\o~ ) {J h'v\i\ e, ~S#rn rak -:.. lj f~~\!((. Of Chemistry J2-Unit l-reaction Kinetics-Notes IS -ti1ml > Page Z of 17pages rt~

3 Chemistry i2-unit I-Reaction Kinetics=Notes Calculations Involving Reaction Rates When doing calculations involving rate, amount (grams, moles, Litres etc.) use the general equation: Rate = L1amount (g, mol, L) L1time (s, min) or I A amount = Rate x A time I or L1time L1amount Rate WHEN YOU USE ONE OF THESE FORMULAS, MAKE SURE YOUR UNITS CAN CANCEL OUT PROPERL Yl AL WAYS use conversion factors to cancel units you don't want and replace them with ones you do want! CO"" t\(5\ on -t-cu...-tq( for ~\'ty1~ Eg.) The rate of a reaction is mol \ m\{\ =- (OC~. mm. \ m\ ('\. or /" C, ~ \5 CoO 5 Express the rate in moll s: It. 'N ANT : \-\ A \J EX. \Gn DW CoO So /' \ \ m\ f\ ro..it. i{\~\ :=..Q.~qlYlil \ v: \ t01fs =- O ~7- \ Eg.) Solid copper dissolves in ni~ acid at a rate of2.43 gl min. How long will it take to dissolve 15.0 g of copper? '------v----" ro.k == ~ ~ h' Y'I\e, =. t 0..~O \1(\ -\ :.\_5_" _0--~L--:--- ~.'-t~ 81m'/(' f'0l ~ 0 Heljuen Questions #1-4 1!.2 c@ A'(\oW\<.-'( W ~j to S()\\l~ W ~f\ \- =- h O\'J--t X 6t;""{= \ S.Dj 'f. \ {'<\ \ (\, ~,L-\ ~ l' ~ \i~e...~ -\~-.-\1--m-\-(\-'\ L- Page 3

4 Chemistry I2-Unit Reaction Rate Calculations: I-Reaction Kinetics=Notes When Conversions Are Needed You also must use molar mass to go grams!:+ moles. m\)\a{ ma~s (at-bml'g ('0a6 s ) Co. (\ be- usul Q -S a." CD (\ V-[if&' \00 -ft.< c-ti>(. Eg) The rate of reaction of zinc metal is given below. Express the rate in units of grams/second: 0.26 mol Zri rmn? g ofzn s W a(\\-- c, h 0..\J.( " \<..V\~ 't-le. n-(.u:l. tt> GOn-J~(1- mc\ ~ 3 An~ 0'(\ '""~ ~()\\ulv\: m;{\~ 5 (b) SCO (\-I~Vs.iOf> tll(,~{s 3_ == o.26 rp~s '/-.tc5.~!3 ~ \~ (Q \ f"\\)\ 2(\ :==. ~5. 1.\ ~ os f<\yf \Mt\ ' w "" 100 s, \ - O,2'03Q --- O,:L~9;5 -- V \ When you have GASES at STP, you can use this conversion to convert from mol ~ L: Q2.4 LI m~'-.. eg.) ~l 02/S = ~ 1/s (at STP) W~ \.eec\ to LonV(l("-\- f'f\\')\ ~ L Solution: W o.n-\- c- n t>. \II( ~ KnoW..h :: o.o~o ~ i..? d\ LtL S s - - \1=06\. NOTE: This conversion is only used for gases at STP! f'(\ \() -= factor ~\ \m, (..... \ f'f"o \_ " ~J,l~ L :::.O.b1-L -O fai-l - s ~\)s ~~.4- L <; ~~.l\ L- \'3\ \ mo \ Try this problem: The rate of a reaction is g ofmg per second. Calculate the number of moles ofmg used up in 6;0 ~tes. <D R (So\- ~' {\~ 4h.e.rnk \ (\ mo 1:. fa-\-.::. 0 I ()~L.\ ~ mi{\ 1\Atl(\" ~Q. lcln -\)1\0. 'N\O~.s ~ 8 '\ll to'(\\h r-\- 3..."t'C\ 0 \ ( \Zo..\e. i- +\UV'I.{-=.. II0'1I)UI'lt-) \ ty\~\ ~..9=- ~L\.~.9 -(0 (j.:) '(\~.t(+- S ~ rn\('\ \ \"0 ( (\ -::::: bo S 'N OS\ \- ~ n C\\j (. '" '" now m~\ ::: tj b34 4c{ t...\ m~\ 'f.. 6n % '20 o. tl '3~q 5 fy1{.)l '{1\\ '" 7i ~L\.~6 \'fy\ \' n m \() ~o\ts 0 ~ t-a~9=- O.0'88QG rn~ 'f.. b -0 r<'(o ::. (), f)t) rno es

5 -Io ChCh"se -from D(l~ Chemistry I2-Unit I-Reaction Kinetics--Notes SP-lLI-eJ to a ()O+h-ef).,/ W-i lyiu6~ C;(b&~ -\-4t-<.- Comparing rates using balanced equations (Crossing the Mole Bridge) mo\ e. b\f\' ~, eg.) ethane 2C2H C02 + 6H20 lco\~a -\- Coef\ iu{~~: -- ~:- t:: 4- : ~ if ethane is consumed at a rate of mol Is, calculate the rate of consumption of 02 in molls mc\c. '\C\.-\io Ot- e-",qi\(., : O~ \ ~ CO,","t(\ mo\ et~a4\..q~ m\)\ 02- ~ : =t- Solution: 'ND.n1- =- no.'j )(. KV\t>\U (j:,y-n.er-s,ic'j\f\ t-ctc-\-o(si. "I~ ~m()\-e.+hthvl tnt!' 09. ::: Q. 066 mo~o.~l '" J rot)\ 02- t-mo\ 0 L - =-ro, ~ '0 mo\ OL.1 ""+ (,(\0\ 02: L:----;t~-~s~ 2.m()\ e\ hla ~ ethane 2C2H C02 + 6H20 '~'. 1-', L+' 6 rcn:\ ~ S ~m~~ if ethane is consumed at a rate of mol /s calculate rate of production ~V Solution: p\ 0."', [n,<,\l-t'c-\- m'd\ e~ha(lq ~ rf\0\ GO.L ' mo\.e.. 'fa. \i o 0 ~ e \-'n a (\G :. CO?. ;l. : L\- ~L~&:: '-- mo \ e-\-hfanl ~ 4-- mo\ tal L\- Me>\ (,02- ~ roo \ e+nla o.l. Page 5

6 Chemistry I2-Unit I-Reaction Kinetics--Notes When other units used - you must covert first to moles (to go over the "mole" bridge) (you may go from L -7 L of one gas to another at STP) Example: 2Al(s) + 3Br2(g) -7 2AlBr3(aq) \'\\C\e f C\-\-\ os '. ~ : B! ~ if 67.5 g of At are consumed per second - calculate the rate of consumption flji\!. "-~1.5~A\ Solution: Cc)~\l~I(s.\on --..,,-- of Br2 in g/s, "-- ~ Must go over the mole bridge! Wa,(\1-- (llk tj... 8('2-?\~'f\ -,s -m L()\\\I-O-\-. 3 A \ -4 :3."Sf 2- \ (Y\\.\s-\ ~ I:> -ho\'c\ -3 A \.~ mi)l A\ ~ ~Cl\ &; Br,. FCtG-\o'C~-7 <D \ M~\ A \ :::. J-:) o 9 '.). \no\ A \ = '3 m"\ t,(l ~ \ ('(\D \ ~(2 = \5'\ '"'39 You may have to use a few conversions and the "rate equation" to arrive at an answer. As you did in Chern. 11, make a "plan" first and make sure your units all cancel the correct way! ~OJ\-\... ""0.\1<. 'f.. \<"I\()W (-h\\q\p W l!oj')-doworksheet1.1 <D 2- CD J Be2... :. tot!;" ~.1-,~ 'j..?\'ot>~_ 'j.. \ s S ~t.\)~:1 r\i~ \ ty\\)~l - S Page 6