Q: For the reaction A ( g ) 2 ~B ( ~g ), the backward reaction rate constant is higher than the forward reaction rate constant by a factor of 2500 , at 1000 K . [Given : R =0.0831 ~L ~atm ~mol ^ -1 ~K ^

aligned K _ C & = K _ f K _ b \\ & = K _ f 2500 ~K _ f \\ & = 1 2500 \\ ~K _ p & = K _ C ( RT )^ n _ g \\ = & 1 2500 (0.0831 1000)^1 \\ ~K _ p & =0.033 aligned

Q: Consider the following reaction in a sealed vessel at equilibrium with concentrations of N _2=3.0 10^ -3 M , O _2=4.2 10^ -3 M and NO =2.8 10^ -3 M . 2 NO _ ( g ) N _ 2( ~g ) + O _ 2( ~g ) If 0.1 mol

aligned & 2 NO _ ( g ) N _ 2( ~g ) + O _ 2( ~g ) \\ & K _ c = [ N _2 ] [ O _2 ] [ NO ]^2 \\ &= 3 10^ -3 4.2 10^ -3 2.8 10^ -3 2.8 10^ -3 \\ &=1.607 \\ & t =0 2 NO _ ( g ) N _ 2( ~g ) + O _ 2( ~g ) \\ & 0.1-0.1 0.05 0.05 \\ & K _ c = 0.05 0.05 (0.1-0.1 )^2 \\ & ~K _ c = 0.05 0.05 0.01(1- )^2 \\ & 1.607= (0.05)^2 ^2 0.01(1- )^2 \\ & ^2 (1- )^2 = 1.607 (0.1)^2 (0.05)^2 aligned gathered 1- = 1.27 0.1 0.05 \\ 1- =2.54 \\ =2.54-2.54 \\ 3.54 =2.54 \\ = 2.54 3.54 =0.717 gathered

Q: In which of the following equilibria, K _ p and K _ c are NOT equal?

aligned & K _ p = K _ c ( RT )^ n _ g \\ & for K _ p K _ c \\ & n _ g 0 \\ & n _ g = n _ p - n _ r aligned (1) n _ g =2-2=0 (2) ng _ g =2-2=0 (3) ng _ g =2-2=0 (4) ng _ g =2-1=1

Question 1

Given below are certain reactions. Identify the reaction for which K_p K_c :

Accepted Answer

The relation between K_p and K_c is given by K_p = K_c(RT)^ n_g , where n_g is the difference between the number of moles of gaseous products and gaseous reactants. For K_p K_c, n_g must be non-zero. For H _2 O (g) + CO (g) H _2 (g) + CO _2 (g) , n_g = 2 - 2 = 0 K_p = K_c For N _2 (g) + 3 H _2 (g) 2 NH _3 (g) , n_g = 2 - 4 = -2 K_p K_c For H _2 (g) + I _2 (g) 2 HI (g) , n_g = 2 - 2 = 0 K_p = K_c For N _2 (g) + O _2 (g) 2 NO (g) , n_g = 2 - 2 = 0 K_p = K_c Answer: N _2 (g) + 3 H _2 (g) 2 NH _3 (g

Question 2

Higher yield of NO in N _2( ~g )+ O _2( ~g ) 2 NO ( g ) can be obtained at [ H of the reaction =+180.7 ~kJ ~mol ^ -1 ] A. higher temperature B. lower temperature C. higher concentration of N _2 D. hig

Accepted Answer

N _2( ~g )+ O _ 2( ~g ) 2 NO _ (g) ; H =+180.7 ~kJ ~mol ^ -1 ( A ) as T reaction shifts forward (B) as T reaction shifts backward (C) as [ N _2 ] reaction shifts forward (D) as [ O _2 ] reaction shifts forward

Question 3

For the reaction A ( g ) 2 ~B ( ~g ), the backward reaction rate constant is higher than the forward reaction rate constant by a factor of 2500 , at 1000 K . [Given : R =0.0831 ~L ~atm ~mol ^ -1 ~K ^

Accepted Answer

aligned K _ C & = K _ f K _ b \ & = K _ f 2500 ~K _ f \ & = 1 2500 \ ~K _ p & = K _ C ( RT )^ n _ g \ = & 1 2500 (0.0831 1000)^1 \ ~K _ p & =0.033 aligned

Question 4

Consider the following reaction in a sealed vessel at equilibrium with concentrations of N _2=3.0 10^ -3 M , O _2=4.2 10^ -3 M and NO =2.8 10^ -3 M . 2 NO _ ( g ) N _ 2( ~g ) + O _ 2( ~g ) If 0.1 mol

Accepted Answer

aligned & 2 NO _ ( g ) N _ 2( ~g ) + O _ 2( ~g ) \ & K _ c = [ N _2 ] [ O _2 ] [ NO ]^2 \ &= 3 10^ -3 4.2 10^ -3 2.8 10^ -3 2.8 10^ -3 \ &=1.607 \ & t =0 2 NO _ ( g ) N _ 2( ~g ) + O _ 2( ~g ) \ & 0.1-0.1 0.05 0.05 \ & K _ c = 0.05 0.05 (0.1-0.1 )^2 \ & ~K _ c = 0.05 0.05 0.01(1- )^2 \ & 1.607= (0.05)^2 ^2 0.01(1- )^2 \ & ^2 (1- )^2 = 1.607 (0.1)^2 (0.05)^2 aligned gathered 1- = 1.27 0.1 0.05 \ 1- =2.54 \ =2.54-2.54 \ 3.54 =2.54 \ = 2.54 3.54 =0.717 gathered

Question 5

For the reaction 2 ~A B + C , K _ C =4 10^ -3 . At a given time, the composition of reaction mixture is: [ A ]=[ B ]=[ C ]=2 10^ -3 M . Then, which of the following is correct?

Accepted Answer

2 ~A B + C , K _ C =4 10^ -3 At a given time t , Qc _ c is to be calculated and been compared with K _ c . aligned & Q _ C = [ B ][ C ] [ A ]^2 = (2 10^ -3 ) (2 10^ -3 ) (2 10^ -3 )^2 \ & Q _ C =1 aligned As Q_c _c, so reaction has a tendency to move backward.

Question 6

For the reaction in equilibrium N _2( ~g )+3 H _2( ~g ) 2 NH _3( ~g ), H =- Q Reaction is favoured in forward direction by:

Accepted Answer

N _2( ~g )+3 H _2( ~g ) 2 NH _3( ~g ), H =- Q According to Le Chatelier's principle. - Exothermic reactions are favoured at low temperature. - Increase in pressure shifts the reaction in direction having lesser number of moles. Hence, the given reaction shifts forward on increasing pressure. - Increasing the concentration of reactants shifts the reaction in forward direction. So high concentration of H _2 shifts reaction in forward direction.

Question 7

In which of the following equilibria, K _ p and K _ c are NOT equal?

Accepted Answer

aligned & K _ p = K _ c ( RT )^ n _ g \ & for K _ p K _ c \ & n _ g 0 \ & n _ g = n _ p - n _ r aligned (1) n _ g =2-2=0 (2) ng _ g =2-2=0 (3) ng _ g =2-2=0 (4) ng _ g =2-1=1

Question 8

At a given temperature and pressure, the equilibrium constant values for the equilibria are given below: 3 ~A _2+ B _2 2 ~A _3 ~B , ~K _1 A _3 ~B 3 2 ~A _2+ 1 2 ~B _2, ~K _2 The relation between K _1

Accepted Answer

3 ~A _2+ B _2 2 ~A _3 ~B ; K _1 2 ~A _3 ~B 3 ~A _2+ B _2 ; K ^ = 1 ~K _1 1 2 A_3 B 3 2 A_2+ 1 2 B_2 ; K_2= K^ K _2= K ^ = 1 K_1

Chemical Equilibrium — Previous Year Questions & Solutions