Chemical Equilibrium: Comprehensive Study Notes, Study notes of Chemistry

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7. Equilibrium

Topic

7 :

Chemical Equilibrium

Total reaction^ (complete reaction)^ : R= Pe (^) one (^) arrow the (^) reaction takes place in (^) one direction. Reversible reaction (^) (incomplete reaction)^ : R= P + 2 arrows

forward reaction^

backward reaction^ -

·^ the^ reaction^

takes (^) place in both (^) directions R

P reaction (^) r2 increases R & step (^) by step^ to reach equilibrium RP T The (^) chemical equilibrium

is reached when^ the rate^ of^ the

forward reactions^ becomes^ equal to^ that^ of the^ negative reaction. => A^ dynamic equilibrium is^ reached

Example

: Respiration (^) % yield (reversible (^) reaction) is low · Hb + 02

HO

=> (^) study (^) equilibrium to^ search^ for new (^) experimental conditions^ to ·^ Hb^ +^ CO (^) , Hb(Uz increase the yield

lungs ·^ Hb^ +^ Co^ - > HbCO^ (toxic)

Equilibrium Law^ :

when the equilibrium is established , [P] and [R] are constant.

Equilibrium constant^ :^ K

aA + bB = cC+ dD

kc (^) : [C] (^) [DJ"k (^) is constant

at constant^

T . [A]" [BJ ex: 2 NOz, N20(9)

KC :

<N20a] (NO (^) ,] acid + alcoholyester^ +^ water

(c = Cester]^ (water]

Lacid][alcohol]

Ox(g)

• (^) 4H(((q) = 2Hz0(g) +^ 2(12(g) (c=^ (H203"^
• (^) [CI]

[02] [Ha]

Equilibrium constant^ of^ the^ reverse^ reaction:

c(+ dD^ -^ >^ aA^ +^ bB

(c:

<AJ"[BJ

so kc'^ =^1 [C] DJ KC Position of^ equilibrum : If KC)^ I

, the^ forward^ reaction^

is (^) favored => (^) products are^ favored over^ reactants

If K(7)^

the backward^ reaction^ is (^) favored => reactants^ are^ favored^ over^ products .

kc

expression :

·water^ is^ solvent

(water] does not

appear

in k

expression . CHsCOOH(aa) +^ He^ O(e)^

CH3COOag) +^ Hy +

caq)

(C :^ SCHy(00-]^ [HaOt]

[CH, COOH] eX H2(g)

(2) +^ 2H((q) at (^) > [Hc] = 0.^3 mol/dm

[12] = 0.^3 meldm

·^ normal^

Hz +2H^

: (^) kc[" CHIJ :^3 mol/dm (^) CH2][12] kc=^ (

KC : ?

K . SHIBIXIwe reaction (^) k< · double wet:^ 2H2 +^212 &Hi :

reverse Ic :

it (^) (C =^ (H1]"^ k: (KC) " half stric^ k = MC (^) CH]"[1 .] coef.

double k(p = (k) )

wef

sum of k(5 =

,+! · reverse : : equ. sum (^) of equations : S(g) +^ 202TS03(g) KCs^ :^

[SOc]

kax K: [S]^ x

(802] [S] 20 (^) .J [s][Oc] [O]LO2]e = [SOs]^ => k(z = (^) kGXk) [S][0.] " =

eX : N2Oq (^) - 2NO^ ,

2N8 .^7 =^0.^8 mol/dms

3 a equilibrium

[Nc0+]^ =^0.

4 mol/dm'

a- Write the (^) expression of KC

KC:^ <NO^ z]

[Nc0 +]

b. Determine (^) the value (^) of KC k=^0. 82 : 1.^6 (^0). 4

c. At an instant T, we^ find [N201] = 06 mol/dms ,^ [NO^ ,]^ =^0.^3 mol/dm

i-^ Calculate^ QCR)

Qu (^) =^ (NO^ 2]^ =^0.

= 0.^15

CN20t] 0.^6

ii.Verify if instant^ T^ corresponds to^ equilibrium

k (^) = 1. (^) 6) Qu = 0.^15 , equilibrium not (^) established (^) at instant T . iii- (^) If not^ state^ in^ which direction the^ equilibrium will (^) shift. Qr > KC^ , (^) products are^ favored

Le Chatelier^ Principle :

• effect^ of^ [

• effect^ of^

  P Effect (^) of concentration :

• effect^ of^ T concentration (^) of reactants^ :

• effect^ of (^) catalyst R =^

P

[R]*Q =^ [P)^ =>^ [RJ^ ↑^ [Q]t

[R] ↑ The (^) equilibrium will^ shift forward (products are^ favoured => yield increases. · The^ stress^ /^ put is^ increasing [R] (^) , equilibrium aims^ to^ work opp of^ the (^) stress (decreasing product) & · (^) To decrease^ [R] (^) ,^ [P]^ must^ increase^ (^ &vice^ versal Concentration (^) of Products^ :

(PTX Q = (PT^ +^ =^ Q^ +

[R] ·The^ Y^ will^ be (^) shifted forward (^) (products are^ favored =% yield % (^) yield ege n (^) --------

• k remains^ constant

In order^ to increase^ the

yield of^ a given chemical reaction^ ,^ use^ high [R] or^ remove^ products when^ it's^ formed ([PJt) Effect (^) of (^) pressure in^ gaseous phase : 3Hz , Na(g) -^ 2 NHy(q) homogenous equilibrium in^ gaseous phase At (^) same volume^ andlemp

Solving

Questions

p

. 190 : (^1) - B is wrong because at equilibrium , I forward rxn = (^) "backward rxn 2 - According

to Chatelier

principle ,^ an (^) increase in

pressure makes^ the

equilibrum shifted^ in order (^) to decrease (^) nor (^) of moles. In this (^) case , in^ the^ reactants'^ side (^) (3 moles) have more br^ of moles than products (2 (^) moles), so (^) products are (^) favored. (^) Therefore , ubr of^ moles^ of (^50) > increases.

• NOTE - In 2502(9)^ +029) = 2SOs The 2 reactions^ are occuring at (^) the same time^ but^ at^ diffrater. If (^) pressure (stress)^ increases^ , equilibrium works to^ reverse^ the^ reaction => decreases nor (^) of moles since (^) Ur> Mp (^) HAS TO BE =>goes to^ the^ products^ (less)^ caseous state k) does^ not^ change.

3. DH70^ =^ uxn^ is^ endothermic

(Pare^ favored

temp (^4) , I (^) will (^) shift , forward^ rxn^ favored^

>k increases

4 - a) (=^

<NO 2] [N20+]

temp

& , forward^ run^ is^ favored horizontal lines^ indicate^ constant^ amount^ of^ R and^ P &equilibrium^ is (^) reached

k ) )^ =>^ for.^ rxn^ is^ favored bJDH >^ O^ ,^ for. rxn^ is^ endothermic According to^ Le Chatelier, when^ Tis^ increased^ the^ products are (^) favored. c] gaseous

molecules in p >

gaseous molecules^

in R

Acc.^ To^ Ch . ↑P ,

-equ shift^ to^ decrease (^) nor (^) of mole.. Rare (^) favored. back is fav