Chemistry 12

Chemistry 12Worksheet 2-1 - Equilibrium, Enthal~

and EntroQY

Unit 2 - Chemical Equilibrium

[K£'1 I1. What do people mean when they say that a reaction is reversible? +hJL r e.a t.... {~()t1

L~_~.A\t9D {f\ +~IL fcv W 6t r) Or' (~V~v~ JL;. fee h DVl .

2. Give four things which are true about a system at equilibrium:

1.

3.

2. ........LJ 0 m it (I'D $ (D)O,"C_ c~..C( (\ {1L {, v.s~/6.k;rn cLb~:l'd k~p / <;. W(/~'f-~1t1~\J '

4. E Cf:}M' 1 ) bvtv) (tvn b-< t;vPl21&a cl,-?t\

What is meant by macroscopic properties? 010 $..< V V ,1- b)0

rpvop~v-h~s (~: C.7-.}OlAV") PVJS~lAV<,

Give some examples of macroscopic properties: c:b I au ;f I ,Pr-L \ <:; u., #'.e/

l+'-DVV/ I-e.ff ornOM'

cUf/l S i'J-,Yl ~'''f)4.

~~J~~)_k~,~~_' _5. What happens to macroscopic properties at equilibrium?_--J...-'Al~D~--=0_lv__ ~--!J. --""",,,-' _

( r..t..W\ t{.." n LbYl ~ t CL;'" I- J '6. How do the rates of the forward and reverse reaction compare at equilibrium? --1~ff

tLv.e. ..L& ~J .

7. Do the forward and reverse reactions stop at equilibrium?_........L../v_'_O_. _

8. What can be said about the concentrations of all reactants and products at equilibrium?

9. Why is chemical equilibrium called dynamic equilibrium? d. ~"l'\ tt ItVl i Ll'V\..i-.tt-ns "ektt-VI g'I·~r 5v 'frv,Dv'/~ ;1" -get' (.1- CiY/H

ch~ it {UvTJ duel" Cl.,~ v,'c<.. V-e.V{ ~ .f

Worksheet 2-1 - Equilibrium, Enthalpy and Entropy Pagel

Chemistry 12 Unit 2 - Chemical Equilibrium

10. Given sufficient activation energy, a system not at equilibrium will eventually move toward~ (A.A' } ,'Iv vr//...Co/L .

11. Systems will tend toward a position of tv\"n /'mum (low) enthalpy.>

12. Systems will tend toward a position of MIt)(,' 'M IA. m ( h (j" ) entropy.

13. Tell whether each of the following is endothermic or exothermic and state which hasminimum enthalpy, the reactants or the products:

a. Cb(g) + PCb (g) ( ) PC15(g) MI = -92.5 kJ

EX 0 thermic and the p t-o J.,lA.- L h have minimum enthalpy.

bD 2NH3(g) E) N2(g) + 3H2(g) All = 92.4 kJ

8NO 0 thermic and the r e.. iL L+- tIll t~ have minimum enthalpy.

~t+

~Iii~cD CI4(g) + H20(g) + 49.3 kJ ( •• CO(g) + 3H2(g)

8/J 00 thermic and the r -e..a.e.t- Ct (l +_.( have minimum enthalpy.

E;NJ)O. -__ 51(~·All = +25 kJ14. If the reaction: Ch(aq) (.. Ch(g)tfD ,'w lL.r-.A )

was proceeding to the right, the enthalpy would be _LJ !-(\.:......=:~:::::..:V~-l.i.=..:.....7L._!_--'ing. Is this a

favourable change? Iv D

15. If the reaction: N2(g) + 3H2(g) <' 2NH3(g) + 92.4 kJ E)(0 .~

was proceeding to the right, the enthalpy would be eLL L V..e. Ct $ ing. Is this a

favourable change? "I e-~

Worksheet 2-1 - Equilibrium, Enthalpy and Entropy Page 2

Chemistry 12 Unit 2 - Chemical Equilibrium16. For each of the following, decide whether the reactants or the products have greater entropy:

a) l2(s) E 0) h(g) The rp u-o d i..-L["f' ~ have greater entropy. R.i.tfl.£lDWl/~( ~,V 11'\ 05· I /'Vi.OJ ,

b) 4PH3(g) E 0) P4(g) + 6H2(g)

__ -----'-- ----'---- --'have greater entropy.

17. When the two tendencies oppose each other (one favours reactants, the other favours

products), the reaction will ( -l"tc(h (:1 6. I-t"-t k of -l.Ll UA"i J " ~'u t4A

IProcesses in which both the tendency toward minimum enthalpy and toward maximum

entropy favour the products, will --1@g.' --v~_.J..h...;..._..;:w;;....;;;...;..VV1...:...;;_Ifl.,;"",l,/....;--f-;;;..t'-·'l ••• ..;.,U...;,I_1_, _

Processes in which both the tendency toward minimum enthalpy and toward maximum

entropy favour the reactants, will __ 11••••.'o-..;.'t- c_/_L.._' _' Ct..--v_'- __ 1--'_--=cd- tvL(._' __ . _

18. F or each ofthe following reactions decide which has minimum enthalpy (reactantsor products),which has maximum entropy (reactantsorproducts), and if the reactants are mixed, what willhappen? (go to completion!reacha stateof equilibrium/notoccurat all).

~ TY\O.9 '-f m O~ /.:a) 4HCl(g) + OZ(g) E 0) 2HZO(g) 0+ 2CIZ(g) + 114.4 kJ \Ex b ')

The -Ip"--'r--tJ---'-_' _cl_S-__ . have minimum enthalpy.

IThe __ ---=-r_~....::e.='".c_~_' .!-1-_' ....::.~'--_. have maximum entropy.

IfHCl + 02 are put together, what should happen?(go to completion!reacha stateofequilibrium/notoccurat all) .) "b ~! . ,rA-.fL Lk 4L..U I', V V IA.....vV\.,

'J- M 0 ~ 'J- j'Vl °5 G "-C02(g) + H2(g) E " CO(g) + H20(g); MI = 42.6 kJ .BNDO )

The r-L,u c J- (:1.- rl J-s. have minimum enthalpy. L ' L. /,~ ~n 0 Dv...---,-o-How does the entropy of the reactants and products compare? S eLi/VI L "/'/1 Ll"'lf.o/~/IfC02(g) +0 H2(g) were put in a flask, what should happen?

(go to completion!reacha stateof equilibrium/notoccurat allno· - 0L (.-u...,.v- 0 V- . L ,I, . 1'1 I r-t..Li...( t-- .

b)

Worksheet 2-1- Equilibrium, Enthalpy and Entropy Page 3

Chemistry 12i-frnoQ' ~,

c) 4PH3(g) E > P4(s) +rYI 0.s6H2(g) + 37 kJ

Unit 2 - Chemical Equilibrium

~y--o)

The ,D"",,' ,--,0),-=--",~:..;:, =--._L..:...../-..:;..$'._, has/have minimum enthalpy,(

The .q:.p~o_-tJ=_).::..cL__.:.· _0_1._L-.-:f:.-.-· ~...:......... has/have maximum entropy,

IfPH3(g) was put in a flask, what should happen?(go tocompletion!reacha stateofequilibrium/not occuratall)

19. Do systems always reach minimum enthalpy at equilibrium? 11 a '-~--------Explain. -rfL12- 4~fV;f!..i/J CtJ ,(Pr- IY1-Cv%' .e11 hPU pi) au

I

20. Do systems always reach maximum entropy at equilibrium? /1,,0.I -~--------

Explain. 1ivL -I~vlc~t LtJ~V' fY\-.L;"-..I, ~..j h aAf(j21. A "heat term" in a chemical equation shows what is happening to the

M t'--'t) k 0JOjIP () S: i .~)'\ v

.£l rvl/~(j=- ~H)and really has nothing to do with the(Answers are either entropy or enthalpy)

22. As a reaction approaches equilibrium, the rate of the forward reaction1

while the rate of the reverse reaction ----')'--'f1'-'--""'c'-",r--"'~~.e=(_c::;:""'.1=,'__. ~",-" _

Once equilibrium is reached, the rates become __ ---.:::C::....·-.-:&=-· _lA_,. _l4_'_l- _

23. Consider the reaction: BaC03(s) + heat E " BaO(s) + C02(g)

Which one of the following observations will indicate that the reaction has most likelyachieved equilibrium?

/ (' j 11 J .., . Irl r- I uf LrL.' f . a-..' ivM, ,+/A.,'/l(,a-) The mass of the system becomes constant ,,'-I-vi 5 t~·2. c , •..f)' , . '.' 1 '. (/') .J

l?Y The concentration ofBaO(s) becomes constant i v'I.. t)1. c/ D ~.<..t'(, S C) '" J..L.jA;. .

.~ All the BaCO~ is consumed.(dL:Jhe gas pressure (or concentration of gas) of the system becomes constant

Your answer is oi . . Explain why. fr.~.[.'$ L.0y--e t $ Cl. lYt Cl DYe) 'SCOJOt C{2LQ ,ae.'IC~ .~~L -fil.J..., P (--t. t <; U. v~.. p r ,r:CI?~J WI' I I b.z.

(A)VlS t- tt>Vvt--· o..t .L-&"j v--t.. II b v\.. L-L ~

24. Consider the following reaction: Fe3+caq)+0 SCN-(aq) E " FeSCN2+(aq)

A solution ofFe(N03)3 is added to a solution ofKSCN. As equilibrium is being established,the [Fe3+]is d.£(ve~a.~/'~ and the [FeSCN2+] J'oev..e..cl{,"r:j .