Kp questions

The first stage in the manufacture of nitric acid is the oxidation of ammonia:

4NH₃(g) + 5O₂(g) --> 4NO(g) + 6H₂O(g) ΔH = −906 kJ mol−1

In modern industrial plants this reaction is carried out at a pressure of around 3 atm. Which of the following statements is incorrect? The raised pressure

• helps push the reactants through the reactor.

• shifts the position of equilibrium to the right.

• increases the cost of the reactor.

• increases the energy cost of this part of the process.

The first stage in the manufacture of nitric acid is the oxidation of ammonia:

4NH₃(g) + 5O₂(g) --> 4NO(g) + 6H₂O(g) ΔH = −906 kJ mol−1

A platinum-rhodium alloy catalyst is used in this reaction. Which of the following statements is incorrect? The catalyst

• lowers the activation energy of the reaction.

• has no effect on the equilibrium constant for the reaction.

• alters the enthalpy change of the reaction.

• reduces the energy cost of this part of the process.

What are the units of the equilibrium constant (K_c) for the hypothetical reaction below?

2A(aq) + B(aq) <=> 4C(aq) + D(aq)

• mol² dm⁻⁹

• mol⁻² dm⁹

• mol² dm⁻⁶

• mol⁻² dm⁶

The reaction between carbon monoxide and hydrogen reaches a dynamic equilibrium.

CO(g) + 2H₂(g) <=> CH₃OH(g)

Which of these statements about a dynamic equilibrium is not true?

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

• The concentrations of the products and reactants do not change.

• The concentrations of the products and reactants are equal.

• The equilibrium can be approached from either direction.

The reaction between carbon monoxide and hydrogen reaches a dynamic equilibrium.

CO(g) + 2H₂(g) <=> CH₃OH(g)

The K_c expression for the above reaction is

• 
• 
• 
• 

The Ostwald Process is a method for making nitric acid. The equation for the first stage of this process is

4NH₃(g) + 5O₂(g) ⇄ 4NO(g) + 6H₂O(g) ΔH=-905kJmol^-1

For this stage of the process, the catalyst is an alloy of platinum and rhodium. A pressure of between 4 and 10 atm and a temperature of 1150 K are used. Unreacted reactants are recycled.

Which one of the following changes will affect the value of the equilibrium constant, K_p?

• Changing the composition of the platinum-rhodium catalyst.

• Increasing the pressure above 10 atm.

• Decreasing the temperature below 1150 K.

• Not recycling unreacted reactants.

For the equilibrium reaction between hydrogen and iodine

H₂(g) + I₂(g) ⇄ 2HI(g)

increasing the pressure of the system

• has no effect on the rate or the position of equilibrium.

• increases the rate but does not affect the position of equilibrium.

• increases the rate and shifts the equilibrium to the right.

• increases the rate and shifts the equilibrium to the left.

For the equilibrium reaction between hydrogen and iodine

H₂(g) + I₂(g) ⇄ 2HI(g)

The equation for the equilibrium reaction between hydrogen and iodine may also be written as

½H₂(g) + ½I₂(g)⇄ HI(g)

This change to the equation, compared to the first equation,

• has no effect on the value of the equilibrium constant.

• halves the value of the equilibrium constant.

• doubles the value of the equilibrium constant.

• square roots the value of the equilibrium constant.

Ammonium chloride decomposes on heating:

NH₄Cl(s) ⇄ NH₃(g) + HCl(g)

The equilibrium constant, Kp, for this reaction equals

• 
• 
• 
• 

Hydrogen and iodine, both with an initial concentration of 0.010 mol dm^-3, were allowed to react. At equilibrium, the concentration of hydrogen iodide was 0.0030 mol dm^-3.

H₂(g) +I₂(g) ⇄ 2HI(g)

Kc is calculated using the values

• A

• B

• C

• D