eqb

Question 1

law of mass action

Answer 1

RATE OF FORWARD REACTION directly propotional to product of active masses[moldm-3] of reactants raise to power coefficient in balanced chemical reaction

aA + bB—->cC +dD

R=kf [A]^a [B]^b (rate of forward)
R=kr [C]^c [D]^d (rate of reverse)

Kc=Kf/kr
hence,

Kc=[C]^c [D]^d / [A]^a[B]^b

Question 2

relationship bwtween kp and kc

Answer 2

Kp= Kc (RT)^change in no. of moles[product-reactant]

R=general gas constant
T=absolute temperature
e.g. N2 +3H2—->2NH3
change in moles (n)= 2-4= -2
Kp=Kc(RT)^-2

*Kp=Kc when change in moles equal zero

*Kp>Kc when moles of product>reactant
e.g PCl5—–>PCl3 +Cl2

Question 3

direction of a chemical reaction

Answer 3

if product/reactant > kc reaction moves BACKWARD
if P/R<kc. reaction moves FORWARD

Product/reactant =Kc, then it reached eqb

Question 4

kc value o extent of reaction

Answer 4

very large kc value= close to eqb
small kc value= shows little forward reaction.
veryy small kc value= very little forward

Question 5

lechateliers principle/effect on eqb by changes

Answer 5

if a system is disturbed it would try to make it normal.

1.Change in conc
> effects direction
>if reactant added/product removed. direstion forward and vice versa

2.change in P, V [unequal no. of moles]
>increase in pressure/decrease in volume=eqb moves forward
>in gases, inc pressure shifts eqb to less moles

3.change in temperature
>for exothermic: (-)
increasing temperature=backward
decreasing temperature=forward

4. effect of a catalyst on kc
   >no effect on kc or position
   >speeds the eqb by lowering Ea

Question 6

haber process and contact process

Answer 6

Haber (exothermic)
N2+ H2—->2Nh3 -92.4

ways to maximize yeild of nh3
>increase pressure………… 200-300atm
>decrease temperature….. 400C [optimum]
>remove product continuosly(ammonia)
*80% used for fertilizers

Contact process

2SO2 + O2—–>2SO3 -194

ways to maximize yeild
>withdraw SO3
>increase pressure……
>decrease temp ………400-500C

H2SO4 king of chemicals. industrial prgress measured by h2so4 manufactured

Question 7

common ion effect

Answer 7

suppresion of ionization of weak electrolyte by adding a common ion.

e.g in purification of NaCl by passing hcl, common ions produced that supress ionization of NaCl.

used in prep of buffers

Question 8

buffers acidic and basic

Answer 8

acidic buffers prepared by mixing weak acid and its salt with strong base

CH3COOH + CH3COONa
PH LESS THAN 7

basicbuffers made by mixing weak base with salt of its strong acid

NH4OH + NH4Cl
PH GREATER THAN 7

Question 9

how do buffers act

Answer 9

act on common ion effect.

dissociation of CH3COOH is supressed due to common ion effect of CH3COO-

CH3COOH + H2O—> CH3COO- + H3O+
CH3COONa———-> CH3COO- + Na

when acid added to this buffer, h+ conc increases. CH3COO- froms CH3COOH.
PH REMAINS almost SAME .
when base added,produceOH- ions which combine with H3O+ to form neutral H2O