Unit 10 Chemistry

When the rate of the forward reaction is equal to the rate of backward reaction, the system is said to be in

• Chemical Equilibrium
• Chemical Balance
• Stoichiometry
• Chemical Reaction

Tags

NGSS.HS-PS1-6

At what time (in seconds) is equilibrium established?

• 0 seconds

• 1 second

• 5 seconds

• 10 seconds

Why is equilibrium called a dynamic state?

• Chemists try to convert as much reactants as possible into products.
• The reactions at equilibrium continue to take place once equilibrium is established.
• 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.

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

• K_c = [NO₂]² / [NO]² [O₂]
• K_c =  [NO]² [O₂] / [NO₂]²
• K_c = [NO]² [O₂] [NO₂]²
• K_c = [NO₂]² / [NO]² +  [O₂]

An equilibrium constant with a large value, e.g. K_c = 1000, indicates…

• A very fast reaction
• Mostly products at equilibrium
• Mostly reactants at equilibrium
• Nothing useful at all

When the following reaction reached equilibrium,

SO_{2 (g)} + NO_{2 (g)} <=> SO_{3 (g)} + NO (g)

it was found to contain:

0.40 M SO₃ , and 0.30 M NO,

0.15 M NO₂ , and 0.20 M SO₂.

Calculate the equilibrium constant for this reaction.

• 4.0

• 0.42

• 0.25

• 1.0

Which is true for a system at equilibrium?

• Forward reaction rate is faster than the reverse and concentrations are equal

• Forward and reverse reaction rates are equal and concentrations are constant

• Forward and reverse reaction rates are equal and concentrations are equal

• Forward reaction rate is faster than the reverse and concentrations are constant

Tags

NGSS.HS-PS1-6

What is the correct equilibrium expression for the following reaction:

2H₂O₂ (aq) ↔ 2H₂O (l) + O₂ (g)

• [H₂O]²[O₂] / [H₂O₂]²

• [H₂O₂]² / [H₂O]²[O₂]

• [O₂] / [H₂O₂]²

• [H₂O]² / [H₂O₂]²

Which is the reactant - and why?

• A, as concentration decreases
• B, as concentration decreases
• A, as concentration increases
• B, as concentration increases

Tags

NGSS.HS-PS1-5

When the system X + 2 Y ↔ Z has reached equilibrium, which of the following is TRUE?

• Forward reaction and Backward reaction stop.
• Forward reaction has sped up and backward reaction has slowed down.
• Forward and backward reactions occur at the same rate.
• Forward reaction has slowed down and backward reaction has sped up.