Chemical Equilibrium.

Define chemical equilibrium.

• A reaction is reversible.

• The concentration of the reactants is equal to the concentration of the products.

• The rate of a forward reaction is equal to the rate of the reverse reaction.

• 
  The reaction stops and no further change in concentration occurs.

Why is equilibrium called a dynamic state?

• 
  Chemists try to convert as much reactants as possible into products.

• The products of a forward reaction are favored, so equilibrium lies to the right.

• 
  All chemical reactions are considered to be reversible under suitable conditions.

• The reactions at equilibrium continue to take place once equilibrium is established.

What is the K_c expression for this reaction?
   2 NO_(g)  +  O_2(g) ⇌  2 NO_2(g)

• 
  K_c = [NO]² [O₂] [NO₂]²

• K_c =  [NO]² [O₂] / [NO₂]²

• 
  K_c = [NO₂]² / [NO]² [O₂]

• K_c = [NO₂]² / [NO]² +  [O₂]

If the reaction quotient Q has a smaller value than the related equilibrium constant, K, _________

• the reaction is at equilibrium

• the reaction is not at equilibrium, and will make more reactants at the expense of the products

• the value of K will not increase until it is equal to Q

• the reaction is not at equilibrium, and will make more products at the expense of the reactants

Changes in pressure will only affect substances that are in the __________ state.

• liquid

• solid

• plasma

• gaseous

For the reaction...

SO₂ + O₂ ⇌ SO₃

If the concentration of SO₂ is increased, the equilibrium of the reaction will shift ___________.

• left

• right

• left and right

• neither left nor right

When K is high,

• There are more products than reactants when the reaction reached equilibrium.

• 
  There are more reactant than products when the reaction reached equilibrium.

• The amount of reactants is equal to the amount of products.

• None of the above

Given: N₂(g) + 3 H₂(g) <---> 2 NH₃(g)

At equilibrium at a certain temperature, the concentration of NH₃(g), H₂(g) and N₂(g) are 0.980 M, 1.53 M and 0.510 M, respectively. Calculate the value of K_c for this reaction.

• 1.26

• 1.96

• 0.526

• 0.837

Which of the following is NOT true at equilibrium?

• The forward and reverse reactions proceed at the same rate.

• 
  The concentrations of reactants and products do not change.

• 
  The concentration of the reactants is equal to the concentration of the products.

• 
  The forward and reverse reactions continue to occur.

If a reaction is reversible and has reached equilibrium, what can be said about the amounts of reactants and products?

• 
  no reactant, all product

• some reactant, some product

• 
  all reactant, no product

• None of the above