Unit 9: Equilibrium Review

Which of the following is true about a system at equilibrium?

• The concentration(s) of the reactant(s) is equal to the concentration(s) of the product(s).
• No new product molecules are formed.
• The concentration(s) of reactant(s) is constant over time.
• The rate of the reverse reaction is equal to the rate of the forward reaction and both rates are equal to zero.

 Equilibrium is reached in chemical reactions when:

• The rates of the forward and reverse reactions become equal.
• The concentrations of reactants and products become equal.
• The temperature shows a sharp rise.
• All chemical reactions stop.

Tags

NGSS.HS-PS1-6

NGSS.HS-PS1-7

NGSS.HS-PS1-4

If the equilibrium constant for A + B ⇌C is 0.175, then the equilibrium constant for  2C ⇌ 2A + 2B is

• 0.650
• 5.71
• 0.175
• 32.7

If the concentration of the product were to double, what would happen to the equilibrium constant?

• Doubles
• Halves
• Quadruples
• Not change

Which of the following is true for a system whose equilibrium constant is relatively small?

• It will take a short time to reach equilibrium.
• It will take a long time to reach equilibrium.
• The equilibrium lies to the left.
• The equilibrium lies to the right.

The reaction quotient for a system is 7.2 × 10². If the equilibrium constant for the system is 36, what will happen as equilibrium is approached?

• There will be a net gain in product
• There will be a net gain in reactant.
• There will be a net gain in both product and reactant
• There will be no net gain in either product or reactant.

For the reaction given, 2.00 moles of A and 3.00 moles of B are placed in a 6.00-L container. A(g) + 2B(g) ⇌ C(g). At equilibrium, the concentration of A is 0.232 mol/L. What is the value of K?

• 1.47
• 1.15
• 0.232
• 4.94

What would happen to the system if oxygen were added:

4NH₃(g) + 5O₂(g) ⇌ 4NO(g) + 6H₂O(g)

• More ammonia would be produced.
• More oxygen would be produced.
• The equilibrium would shift to the right.
• The equilibrium would shift to the left.

For a certain reaction at 25.0°C, the value of K is 1.2 × 10^–3. At 50.0°C the value of K is 0.34. This means that the reaction is

• Exothermic
• Endothermic
• Isothermic
• Can't tell

What is the equilibrium expression for:
Fe₃O₄(s) + 4H₂(g) ⇌ 3Fe(s) + 4H₂O(g)

• ([Fe]³[H₂O]⁴ ) / ([Fe₃O₄][H₂]⁴)
• ([Fe₃O₄][H₂]⁴)/ ([Fe]³[H₂O]⁴)
• [H₂O]⁴ / [H₂]⁴
• ([Fe][H₂O]) / ([Fe₃O₄][H₂])