15.1.1 The Concept of Equilibrium

Question 1

For a reaction A+B —> AB, the value of the equilibrium constant is less than 1. Therefore, which of the following statements is correct?

Answer 1

Equilibrium lies toward the formation of the reactants.

Question 2

Is the following statement true or false?

The value of the equilibrium constant can be negative.

Answer 2

false

Question 3

In a forward reaction, a new product is formed from the reactants. In a backward reaction, the products are converted back to the original reactants. At equilibrium, which of the following statements is correct?

Answer 3

The rate of the forward reaction is equal to the rate of the backward reaction.

Question 4

H2 (hydrogen) reacts with I2 (iodine) to give HI (hydrogen iodine).
H2 + I2 —> 2HI
At equilibrium the partial pressure of H2, I2, and HI are Ph, Pi, and Phi. The equilibrium constant can be calculated by using which of the following expressions?

Answer 4

PHI2 / PH2PI2

Question 5

For a particular endothermic reaction, heat is required for the reactant molecules to overcome the activation-energy barrier and to react to form the product molecules. Which statement about this reaction is correct?

Answer 5

Increasing the temperature of the reaction increases the value of the equilibrium constant.

Question 6

Is the following statement true or false?

If the value of the equilibrium constant is greater than 1, then the equilibrium position lies toward the formation of the products.

Answer 6

true

Question 7

x moles of hydrogen are added to y moles of iodine, and z moles of hydrogen iodide are formed. What is the value of the equilibrium constant?

Answer 7

z 2 / [(x − z/2) (y − z/2)]

Question 8

A reaction reaches equilibrium in four hours. The equilibrium constant for this reaction is K1. A catalyst is added to this reaction, the reaction rate increases, and equilibrium is reached in one minute. The equilibrium constant for this reaction is K2. How are K1 and K2 related?

Answer 8

K1 = K2

Question 9

Consider the following reaction: N2(g) + 3H2(g) —> 2NH3(g)

At the start of a reaction 0.071 mol/L of N2, 0.0092 mol/L of H2, and 0.00018 mol/L of NH3 are put in an enclosed vessel at 375 degrees C. If the equilibrium constant for the reaction is 1.2, which of the following statements is NOT correct?

Answer 9

The reaction is at equilibrium and therefore, no reaction will occur.

Question 10

In the following reaction PCl5 dissociates to give PCl3 and Cl2.

PCl5(g) —> PCL3(g) + Cl2(g)

The partial pressure of PCl5, PCl3, and Cl2 are 0.875 atm, 0.463 atm, and 1.98 atm, respectively. The value of the equilibrium constant is _________.

Answer 10

1.05