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Chemistry 12-Unit I-Reaction Kinetics=Notes
Chemistry 12
1.1 Notes - Reaction Kinetics
Reaction Kinetics is the study of rates and the factors which affect the rates.
ExpressingRates
rate = ~guantity of a product formedf:l time
or rate = _~guantity of a reactant consumed~time
in general: rate = ~ amount (a reactant or product)~time
If you have .... IlAmount 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
Note: A time unit is always in the denominator of a rate equation.~'- ~i(\ .) S .l hrJ cl~.
• Any species can be measured in ~ moles/ ~ time• Note: We don't measure the concentrations (~ molarity) of pure liquids (ex: H20) and
solids since they have constant densities (basically constant concentrations).
Chemistry 12-Unit l-Reaction Kinetics-Notes Page 1 of 17pages
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 ofZnLl time
r = Ll [HCI]Ll time
(note: [] = molarconcentration)
fo. ~: t"\-sr = Ll mass of container (as H2 (g) escapes)
Ll timer = Ll volume H2
Ll time
Spectator Ions
- some rxs, when written in ionic form show that some ions don'tchange 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: Towritean 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
ra k -:..lJ f~~\!((. Of rt~IS -ti1ML >
Page Z of 17pagesChemistry J2-Unit l-Reaction Kinetics-Notes
Chemistry i2-Unit I-Reaction Kinetics=Notes
Calculations Involving Reaction Rates
When doing calculations involving rate, amount (grams, moles, Litres etc.) use the generalequation:
Rate = L1amount (g, mol, L)L1time (s, min)
or L1amountRate
L1time
or I A amount = Rate x A time IWHEN YOU USE ONE OF THESEFORMULAS, MAKE SURE YOURUNITS CAN CANCEL OUT PROPERL Yl
ALWAYS use conversion factors to cancel units you don't want and replace them with ones youdo want! CO"" t\(5\ on -t-CU...-TQ( for ~\'tY1~
\ m\{\ =- (OC~.
/" C, ~ \5 CoO 5Express the rate in moll s: It.
'NANT : \-\ A \J EX.· \Gn DW CoO So__/' \ \ m\ f\ro..It. i{\~\ :=. .Q.~qlYlil \ v: \ t01fS =- O.0003~ 7- \
Eg.) Solid copper dissolves in ni~ acid at a rate of2.43 gl min. How long will it take todissolve 15.0 g of copper? '------v----"
ro.k == ~. 4- 3 .9.
Eg.) The rate of a reaction is 0.020 molmm. \ m\ ('\. or
5
~ h' Y'I\e, =. t 0..~O \1(\ -\- - ---.:.\_5_" _0--~L--:---~.'-t~ 81m'/('
f'0l ~ 0 Heljuen Questions #1-4 1!.2
c@ A'(\oW\<.-'( W ~j to S()\\l~
W ~f\ \- =- h O\'J--t X
6 t;""{= \S .Dj 'f. \ {'<\ \ (\ ,
~,L-\ ~ l'~ \i~e...~ -\~-.-\1--m-\-(\-'\
L-
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Chemistry I2-Unit I-Reaction Kinetics=Notes
m\)\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:
Reaction Rate Calculations: When Conversions Are Needed
You also must use molar mass to go grams !:+ moles.
0.26 mol Zrirmn
? g ofZns
't-le. n-(.u:l. tt> GOn-J~(1- mc\ ~ 3An~ 0'(\ '""~ ~()\\ulV\: m;{\~ 5
W a(\\-- c, h 0..\J.( " \<..V\~ (b) SCO (\-I~Vs.iOf> tll(,~{S3_ == o .26 rp~S '/-.tc5.~ !3 ~ \~ (Q \ f"\\)\ 2(\ :==. ~5. 1.\ ~oS f<\yf \Mt\ '
w ""
100 s, \ V \ f'(\ \ () -= ~\)s- O,2'03Q - O,:L~9;5- --- --
When you have GASES at STP, you can use this conversion factorto convert from mol ~ L: Q2.4 LI m~'-.. ----- ~\ .•...• ~~.4- Leg.) 0.030 ~l 02/S = ~ 1/s (at STP)
W~ ¥\.eec\ to LonV(l("-\- f'f\\')\ ~ LSolution:
W o.n-\- c- n t>. \II( ~ KnoW..h :: o.o~o ~ i.. ? d\ LtLS s - - \1=06\ .
\m, (.
\ f'f"O \_
" ~J,l~ L
:::.O.b1-L-O·fai-L-s
<; ~~.l\ L-\'3\
\ mo \
NOTE: This conversion is only used for gases at STP!
Try this problem:
The rate of a reaction is 0.034 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{\
o @ 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 (. '" '" nowm~\ ::: 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
Chemistry I2-Unit I-Reaction Kinetics--Notes-Io ChCh"se -from D(l~
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.) ethane2C2H6 + 702 -7 4C02 + 6H20
lco\~a·-\- Coef\ iu{~~: -- ~:- t:: 4- : ~if ethane is consumed at a rate of 0.066 mol Is, calculate the rate ofconsumption 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.+htHVLtnt!' 09. ::: Q. 066 mo~o.~L '" J rot)\ 02- t-MO\ 0 L -
~ S ~m~~=-ro , ~ '0 mo\ OL.1 ""+ (,(\0\ 02:L:----;t~-~s~__ 2.m()\ e\··hlA ~
ethane2C2H6 + 702 -7 4C02 + 6H20
'~'. 1-', L+' 6 rCn:\if ethane is consumed at a rate of 0.066 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.
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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 fC\-\-\ os '. ~ : B! ~if 67.5 g of At are consumed per second - calculate the rate of consumption of Br2 in g/s,
"-- ~--..,,--• Must go over the mole bridge! Wa,(\1--· (llk tj.... 8('2-
SflJI\!. "-~1.5~A\
Solution:?\~'f\ -,s -m L()\\\I-O-\-. 3·A \ -4 :3."Sf 2-
\ (Y\\.\s-\ ~ I:> -ho\'C\ -3 A \ .~ mI)l A\ ~ ~Cl\ &;1. 949 Br,.
Cc)~\l~I(s.\on 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 youdid in Chern. 11, make a "plan" first and make sure your units all cancel the correct way!
~OJ\-\ ... ""0.\1<. 'f.. \<"I\()W (-h\\Q\P W l!OJ')-Doworksheet1.1<D 2- CDJ Be2... :. toT!;" ~ .1- ,~ 'j.. ?\'Ot>~_ 'j.. \511-13.
S ~t.\)~:1 r\I~ \ tY\\)~Ls--
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