Equilibrium

Equilibrium

Do you understand the concepts?

Multiple Select

Which of these are features of a Dynamic Equilibrium?

• has to be in a closed system

• The rate of the forward and reverse reactions are the same

• the concentrations of the reactants and products are the same

• the concentrations of the reactants and products remain constant

Fill in the Blanks

Le Chatelier's principle states that when a system in equilibrium is subjected to a a change, the position of equilibrium will shift to

the change.

What is the missing word?

Multiple Select

 $2SO_{2_{\ }}\ \ \left(g\right)\ \ \ \ +\ \ \ \ \ O_2\ \ \ \left(g\right)\ \ \ \ \ \ \ \ \leftrightarrow\ \ \ \ \ \ \ 2SO_{3_{ }}\ \ \ \left(g\right)$  
If concentration of  $SO_{2_{ }}$  is increased, equilibrium will shift...

• Left

• Right

• stay the same

Multiple Select

 $2SO_{2_{\ }}\ \left(g\right)\ \ \ +\ \ \ O_2\ \left(g\right)\ \ \ \ \ \ \leftrightarrow\ \ \ \ \ 2SO_{3_{ }}\left(g\right)\ \ \ \Delta H\ =\ -197\ kJmol^{-1}$  

If the temperature is increased, the equilibrium will shift ... 

• left

• right

• stay the same

Multiple Select

 $2SO_{2_{\ }}\ \ \left(g\right)\ \ \ \ +\ \ \ \ \ O_2\ \ \ \left(g\right)\ \ \ \ \ \ \ \ \leftrightarrow\ \ \ \ \ \ \ 2SO_{3_{ }}\ \ \ \left(g\right)$  

If a catalyst is added, the equilibrium will shift...

• left

• right

• stay the same

Multiple Select

 $2SO_{2_{\ }}\ \ \left(g\right)\ \ \ \ +\ \ \ \ \ O_2\ \ \ \left(g\right)\ \ \ \ \ \ \ \ \leftrightarrow\ \ \ \ \ \ \ 2SO_{3_{ }}\ \ \ \left(g\right)$  
If the pressure is increased, equilibrium will shift ...

• left

• right

• stay the same

 $N_2\ \left(g\right)\ +\ 3H_2\ \left(g\right)\ \leftrightarrow\ 2NH_3\ \left(g\right)\ \Delta H\ =\ -92kJmol^{-1}$  

Multiple Select

 $N_{2_{ }}\left(g\right)\ +\ 3H_2\ \left(g\right)\ \leftrightarrow\ 2NH_3\ \left(g\right)\ \ \Delta H\ =-92kJmol^{-1}$  

Select the conditions that would favour the formation of a large amount of product

• High Temperature

• Low temperature

• High pressure

• Low pressure

Open Ended

Explain why low temperature and high pressure are the best conditions to produce maximum yield of ammonia

 $N2​​(g)+3H2​(g)↔2NH3​(g)ΔH=−92kJmol−1$  

The haber process

 $N2​​(g)+3H2​(g)↔2NH3​(g)ΔH=−92kJmol−1$  

Low temperatures push eqm right because the reaction is exothermic in the forward direction.

High pressure pushes eqm right because there are fewer moles of gas on the right.

Multiple Select

What conditions are actually used for the haber process?

• High Temperature

• Low temperature

• High Pressure

• Low pressure

Open Ended

Why is a high temperature and pressure used for the haber process?

Compromise conditions are used for the Haber process

• High temperatures will lower the yield of ammonia being made but will increase the rate of reaction

• High pressures force eqm to the right, but not too high that it is too costly in terms of energy or specialist equipment.

• An iron catalyst is used to further increase reaction rate and reduce energy costs.

The Equilibrium Constant K_c

• The value of K_c is an indication of the position of equilibrium

• If K_c = 1, the position of eqm lies in halfway between the reactants and products

• if K_c > 1, eqm lies to the right/products

• if K_c < 1, eqm lies to the left/reactants

• The greater the value of K_c, the further to the right the position of eqm lies.

Multiple Choice

Which of these would be the correct expression of Kc for the Haber process?

•  $Kc\ =\ \frac{\left[NH_{3_{ }}\right]^2}{\left[N_2\right]\left[H_2\right]^3}$  

•  $Kc\ =\ \frac{2\left[NH_3\right]^{ }}{\left[N_2\right]3\left[H_2\right]^{ }}$  

Fill in the Blanks

In the manufacture of ammonia at 400 degrees C, the equilibrium concentrations are:
Nitrogen = 18.6 M, Hydrogen = 0.900 M, ammonia = 1.50 M.

 $N_{2\ }+\ 3H_2\ \leftrightarrow\ 2NH_3$  
Calculate Kc (to an appropriate number of sig figs).