Question

Consider the following system at equilibrium where AH 87.9 kJ/mol, and Ke 1.20x102, at 500 K. PCI5(g)=PCl3()+ Cl2(®) If the TEMPERATURE on the equilibrium system is suddenly increased: The value of K A. increases. B. decreases. C. remains the same. A. is greater than Ke The value of Q B. is equal to K C. is less than Ke A. run in the forward direction to reestablish equilibrium The reaction must: B. run in the reverse direction to reestablish equilibrium C. remain the same. It is already at equilibrium. The concentration of Cl2 will: A. increase. B. decrease. C. remain the same.

Answer 1

Answer:

For 1: The correct answer is Option A.

For 2: The correct answer is Option C.

For 3: The correct answer is Option B.

For 4: The correct answer is Option A.

Explanation:

We are given:

$K_e=1.20\times 10^2k$

$\Delta H^o_{rxn}=87.9J/mol$

As, enthalpy of the reaction is positive. So, it is an endothermic reaction.

For an endothermic reaction, heat is getting absorbed during a chemical reaction and is written on the reactant side.

$A+\text{heat}\rightleftharpoons B$

Any change in the equilibrium is studied on the basis of Le-Chatelier's principle.  This principle states that if there is any change in the variables of the reaction, the equilibrium will shift in the direction to minimize the effect.

As, heat is getting absorbed during a chemical reaction. This means that temperature is getting increased on the reactant side. If the temperature in the equilibrium is increased, the equilibrium will shift in the direction where, temperature is getting decreased. Thus, the reaction will shift in right direction that is towards the product.

• For 1:

There are 3 conditions:

• When $K_{e}>1$; the reaction is product favored.
• When $K_{e}<1$; the reaction is reactant favored.
• When $K_{e}=1$; the reaction is in equilibrium.

On increasing the temperature of the system, the equilibrium is shifting to right direction. This means that more and more product is getting formed which increases the value of $K_e$

Hence, the correct answer is Option A.

• For 2:

'K' is the constant of a certain reaction at equilibrium while 'Q' is the quotient of activities of products and reactants at any stage other than equilibrium of a reaction.

There are 3 conditions:

• When $K_{e}>Q$; the reaction is product favored.
• When $K_{e}<Q$; the reaction is reactant favored.
• When $K_{e}=Q$; the reaction is in equilibrium.

As, the value of $K_e$ is getting increased. This means that value of 'Q' is less than the equilibrium constant.

Hence, the correct answer is Option C.

• For 3:

As, the reaction is proceeding the forward direction. So, to re-establish equilibrium, the reaction must proceed in the backward (reverse) direction to counter the effect.

Hence, the correct answer is Option B.

• For 4:

For the given chemical reaction:

$PCl_5(g)\rightarrow PCl_3(g)+Cl_2(g)$

Chlorine gas is present on the product side and the reaction is going in the forward direction.

This means that more and more product is getting formed. So, the concentration of products will increase. This increases the concentration of chlorine gas.

Hence, the correct answer is Option A.