Chemical and Ionic Equilibrium - Result Question 6

####6. Two solids dissociate as follows:

A(s)B(g)+C(g);Kp1=xatm2 D(s)C(g)+E(g);Kp2=yatm2

The total pressure when both the solids dissociate simultaneously is

(2019 Main, 12 Jan I)

(a) x+y atm

(b) x2+y2 atm

(c) (x+y)atm

(d) 2(x+y)atm

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Answer:

Correct Answer: 6. (c)

Solution:

  1. The equilibrium reaction for the dissociation of two solids is given as:

At equilibrium

A(s)B(g)+C(g)

Kp1=x=pBpC=p1(p1+p2)

Similarly, D(s)C(g)+E(g)

At equilibrium

Imp2=y=pCpE=(p1+p2p2)p2

On adding Eq. (i) and (ii), we get.

Kp1+Kp2=x+y=p1(p1+p2)+p2(p1+p2)

=(p1+p2)2

or x+y=p1+p2

Now, total pressure is given as

pT=pB+pC+pE =p1+(p1+p2)+p2 =2(p1+p2)

On substituting the value of p1+p2 from Eq. (iii) to Eq. (iv), we get

pT=2x+y



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