15.3.1 Le Châtelier's Principle Flashcards Preview

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Flashcards in 15.3.1 Le Châtelier's Principle Deck (12)
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1
Q

Le Châtelier’s Principle

A
  • Le Châtelier’s principle states that a system in equilibrium that is subjected to a stress will react in a way that tends to relieve the stress.
  • Le Châtelier’s principle can be explained using the reaction quotient (Q).
2
Q

note

A
  • Le Châtelier’s principle states that a system in equilibrium that is subjected to a stress will react in a way that tends to relieve the stress.
  • For example, hydrogen (H 2 ), iodine (I 2 ), and hydrogen iodide (HI) are allowed to reach equilibrium. When more I 2 is added (a stress), the system responds by running the forward reaction and reducing the concentration of I 2 (relieving the stress). When the new equilibrium is established, the ratio of products to reactants is the same as at the original equilibrium (K eq).
  • Le Châtelier’s principle can be explained using the reaction quotient (Q).
  • For example, hydrogen iodide (HI) is added to an empty container. Initially, Q is very large. The HI decomposes into hydrogen (H 2 ) and iodine (I 2 ) until Q = K eq . When more I 2 is added (a stress), the denominator of Q increases, and therefore the value of Q decreases. The reaction then progresses from left to right (relieving the stress) until Q = K eq . If H 2 is then removed (a stress), the denominator of Q decreases, and therefore the value of Q increases. The reaction then progresses from right to left (relieves the stress) until Q = K eq .
3
Q

When carbon dioxide dissolves in water, an extremely small amount of a substance, called carbonic acid (H2CO3 ), is present at equilibrium. CO2 (g) + H2O(l) ↔ H2CO3 (ag)

Which statement, based on Le Châtelier’s principle, about this system is not correct?

A

The value for Keq of this reaction must be large. In addition, if some H2CO3 is removed, more CO2 will be produced to relieve the stress.

4
Q

Let’s examine the reaction of hydrogen gas and iodine gas to form HI gas.

H2(g) + I2(g) ↔ 2HI(g)

The diagram shows the varying concentrations of the gases during different stages in the reaction. Which statement about this reaction is not correct?

A

Stage B is an instantaneous stage in which more product is suddenly added to the system.

5
Q

Look at the reaction for the synthesis of ammonia from nitrogen and hydrogen.

N2(g) + 3H2(g) ↔ 2NH3(g)

Which of the following does not result in the production of NH3 gas?

A

Removing some N2 gas from the system

6
Q

Which statement about Le Châtelier’s principle is not correct?

A

Adding more reactant to an equilibrium system will cause the reverse reaction to occur.

7
Q

Look at the reaction quotient diagram for the reaction of H2(g) + I2(g) ↔ 2HI(g). The value for Q at any point in this reaction is [HI]2 / [H2 ] [ I2 ].

Which statement about this reaction is not correct?

A

At Point 1 in the reaction, Q is greater than Keq.

8
Q

Which statement best defines Le Châtelier’s principle?

A

When a stress is applied to a system that is at equilibrium, the system will respond by minimizing the stress.

9
Q

Which statement about Le Châtelier’s principle is not correct?

A

A system at equilibrium will favor the product side of a reaction when under stress.

10
Q

In the reaction for the synthesis of ammonia, nitrogen and hydrogen react to form ammonia.

N2(g) + 3H2(g) ↔ 2NH3(g)

Which statement about this reaction is not correct?

A

Adding more ammonia causes the equilibrium to shift toward the reactants, depending on the value of Keq.

11
Q

Look at the following reaction involving four gases.

4NH3(g) + 3O2(g) ↔ 2N2(g) + 6H2O(g)

Which statement about this reaction is not correct?

A

An increase in the number of O2 molecules will cause the value of Q to be greater than Keq.

12
Q

Le Châtelier’s principle can be applied to the atmosphere. Carbon dioxide gas is in equilibrium with carbon dioxide dissolved in ocean waters. When fossil fuels are burned, more carbon dioxide gas is released to the atmosphere. Which statement about this equilibrium is not correct?

A

The ocean water will absorb all of the excess carbon dioxide gas released into the atmosphere.

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