Chemistry I2-Unit I-Reaction Kinetics--Notes ~,\\ t.)<p\C\\{\ b€\o~ 1.) 1.2 Notes - Measuring Reaction Rates - different methods for different reactions. - some changes are easier to measure than others! Monitoring Reaction Rates - properties which can be monitored (measured at specific time intervals) in order to determine rx. rate. We must consider: ~ !1,'1l u~ 1".fo o.hou+- p.-ofl2.l4i ~J \lJ~ • -subscripts (s) (1) (g) (aq) CtAA \ A t(\ {A S ' , • coefficients of gases U.(..(,. . f' • heat (endo or exo?) Here are the properties that we often measure experimentally: (1) Colour change (2) Temp changes (3) Volume changes (4) Mass changes (5) Change in Concentration (Molarity) (6) Change in Acidity, lH1 Colour changes - good choice if a coloured reactant is consumed or new coloured product is formed. eg.) CU(s) + 4HN03(aq) -7 copper clear - in this case could measure: r 0. k- b CO\C\k( " (\4os\ ~ £) +, ("()~ Rate= ~ 13\",<. \(\-knsi~ ().n m<..., or Rate = ~ Brow(\ \(\-\{nsi ~ b tfM(" - colour intensity can be measured quantitatively using a spectrophotometer (see p. 4 in Hebden.) Chemistry I2-Unit l-Reacuon Kinetics-Notes Page 7 of 17 pages
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Chemistry I2-Unit I-Reaction Kinetics--Notes
~,\\t.)<p\C\\{\
b€\o~
1.)
1.2 Notes - Measuring Reaction Rates
- different methods for different reactions.- some changes are easier to measure than others!
Monitoring Reaction Rates
- properties which can be monitored (measured at specific time intervals) inorder to determine rx. rate.
We must consider: ~ !1,'1l u~ 1".fo o.hou+- p.-ofl2.l4i ~J \lJ~• -subscripts (s) (1) (g) (aq) CtAA \ A t(\ {A S '
, • coefficients of gases U.(..(,. .
f' • heat (endo or exo?)
Here are the properties that we often measure experimentally:(1) Colour change(2) Temp changes(3) Volume changes(4) Mass changes(5) Change in Concentration (Molarity)(6) Change in Acidity, lH1
Colour changes- good choice if a coloured reactant is consumed or new coloured product is formed.
eg.) CU(s)+ 4HN03(aq) -7copper clear
- in this case could measure: r0.k - b CO\C\k( "(\4os\ ~£) +, ("()~
Rate= ~ 13\",<. \(\-knsi~().nm<...,
or Rate = ~ Brow(\ \(\-\{nsi ~b tfM("
- colour intensity can be measured quantitatively using a spectrophotometer(see p. 4 in Hebden.)
Mass changes* we can measure mass if a solid is being used up/produced. Also when a gas is escaping(measure the change in mass of container and contents).
rak=- t f(\ ().S~c+.- \J\i-----t -h'Mv• if only one solid is used up
- could remove Mg solid periodically and weigh it:
Chemistryi2-Unit I-Reacti n Kinetics-Notes Page 8 of 17pages
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Chemistry i2-Unit I-Reaction Kinetics=Notes
• if one gas is produced and escapes, measure mass of what's left in container(mass of container and contents) , 8a (' Pihc\\A..(.-t-
eg) heat + CaC03(s) ~ CaO(s) C02(g) -<t:::~i
rate = L1 mass of container & contentsL1 time of6NL-------------~~S~$r~M\
Note: it's not practical to measure masses of (aq) substances separately since they are mostly
water. eg) ClI(S) E<;J-7orH2(g) ~3h;)A mass ofHNOJ~ .• fngtia~cePtaPIFj
A time~ \\\.ea~U(ema s s O~L..'\ -\OY- So\\ dS }(9 as
piOau(;~.6.) Changes in Concentration (for specific ions)
Note: Does the [Br -] change? _ND Explain.\ije S-(.l eqU.ll\ am(.)\l\\-ts of- B-;- on r~t-\-£\(\+ a~ pvotA.uvt-sr cA<.~· I.+ \~ t\. SeE"G-rfr'1"o~ \ t)rJ 1
The concentration ola specific ion can be measured:- using spectrophotometer ~f- t.t. \ ou c~ .- periodic samples taken and titrated to measure cone.
Chemistry I2-Unit l-Reaction Kinetics-Notes Page 9 of 17pages
~liIJIJ-[/!l/I j-j(eoClion Kinetics-Notes
7.) Changes \n Ac~~tW
_ special case of #6rat~ = 1:1 (H+l
~tim~
~; Q~~~ ~-fJeasure of acidityv Ij \o\M [J.\"tl 'pH Q 7 J_ 14 \ \< > ~n Sea \-G .
more acidic more basic -(less basic) (less acidic) -W-( '('(IO{-l It 1- PV..Q ~.((\-\- ; II.- ~
• iCM-' SC>\\A HoA .. .. +1iI... \A"D/ /J
H' is a reactant ( II ••, v+ ..l or any acid nci, HN03
etc.) ,,(J0\ (,. f' \ 0 \AI P H '\ .[H 1will aery.fA':./.... \, , • J