Question

The solid XY decomposes into gaseous X and Y: XY(s) ⇌ X(g) + Y(g) Kc = 4.1(at 0C) If the reaction is carried out in a 1-L container, which initial amounts of X and Y result in the formation of solid XY?

Answer 1

This is an incomplete question, here is the complete question.

The solid XY decomposes into gaseous X and Y:

$XY(s)\rightleftharpoons X(g)+Y(g)$  Kp = 4.1 (at 0°C)

If the reaction is carried out in a 1 L container, which initial amounts of X and Y will result in the formation of solid XY?

a) 5 mol X; 0.5 mol Y

b) 2.0 mol X; 2.0 mol Y

c) 1 mol X; 1 mol Y

d) All of the above

Answer : The correct option is, (D)

Explanation :

Reaction quotient (Q) : It is defined as the measurement of the relative amounts of products and reactants present during a reaction at a particular time.

The given balanced chemical reaction is,

$XY(s)\rightleftharpoons X(g)+Y(g)$

The expression for reaction quotient will be :

$Q=[X][Y]$

In this expression, only gaseous or aqueous states are includes and pure liquid or solid states are omitted.

The given equilibrium constant value is, $K_p=4.1$

Equilibrium constant : It is defined as the equilibrium constant. It is defined as the ratio of concentration of products to the concentration of reactants.

If the initial amount of X and Y to form XY then the product of their product must be greater than Kp.

Now we have to calculate the product of partial pressure.

PV = nRT

$P=\frac{nRT}{V}$

Moles of X      Moles of Y      Pressure of X     Pressure of Y       Q

    5.0                    0.5                  112.1                     11.2                1255.52

     2                        2                    44.8                    44.8               89.6

     1                         1                     22.4                    22.4               44.8

There are 3 conditions:

When $Q>K_c$ that means product > reactant. So, the reaction is reactant favored.

When $Q$ that means reactant > product. So, the reaction is product favored.

When $Q=K_c$ that means product = reactant. So, the reaction is in equilibrium.

From the above we conclude that, in all the three options $Q>K_c$ that means product > reactant. So, the reaction is reactant favored that means reaction must shift to the reactant (left) to be in equilibrium.

Hence, the correct option is, (D)