Question

Reaction for part 1

Reaction: CrO42-(aq)+2H+(aq) <--> Cr2O72-(aq)+H2O(l)

YELLOW ORANGE

a) Under what conditions will Cr2O72-(aq) predominate? explain / defend your answer choice.

b) is this a redox reaction? explain/ defend your answer.

2) Given the following reaction

heat + CaCO3(s) <--> CaO(s) + CO2(g)

a. In which direction, if any, will the equilibrium shift when the pressure of CO2 is increased?

b. In which direction, if any, will the equilibrium shift if the temperature is decreased?

c. In which direction, if any, will the equilibrium shift if the amount of CaCO3 is increased?

3) Using the same reaction from question 1

Reaction: CrO42-(aq)+2H+(aq) <--> Cr2O72-(aq)+H2O(l)

YELLOW ORANGE

If sulfuric acid (H2SO4) is added to this solution, will a color change be observed? If so, how does the addition of sulfuric acid result in a color change? Explain your reasoning by showing the effect of the addition of H2SO4 on the equilibrium for the reaction.

4)

Using the same reaction from question 1

Reaction: CrO42-(aq)+2H+(aq) <--> Cr2O72-(aq)+H2O(l)

YELLOW ORANGE

If sodium hydroxide (NaOH) is added to the solution, will a color change be observed? If so, how does the addition of sodium hydroxide result in a color change? Explain your reasoning by showing the effect of the addition of NaOH on the equilibrium for the reaction.

5) How can we demonstrate that equilibrium is a dynamic process by running an experiment? Please provide a specific example.

Answer 1

Cr2O72-(aq) predominates in acidic conditions where additional H+ ions shift the equilibrium right, resulting in an orange color. The reaction is not a redox reaction, as there is no change in oxidation states. Adding sulfuric acid results in an orange color, whereas adding NaOH results in a yellow color, visually demonstrating dynamic equilibrium.

Step-by-step explanation:

Conditions for Predominance of Cr2O72-(aq)

To determine under what conditions Cr2O72-(aq) will predominate, we can refer to the equilibrium:
CrO42-(aq) + 2H+ (aq) <--> Cr2O72-(aq) + H2O(l).
Cr2O72-(aq) will predominate in acidic conditions because an increase in H+ ions shifts the equilibrium to the right, in accordance with Le Chatelier's Principle.

Is This a Redox Reaction?

This is not a redox reaction because there is no change in the oxidation states of the elements involved. Both species contain chromium in the same oxidation state, -2 for oxygen and +6 for chromium.

Effects of Adding Sulfuric Acid (H2SO4)

Adding sulfuric acid to the solution will introduce more H+ ions, shifting the equilibrium to the right to form more Cr2O72-(aq), resulting in an observable color change from yellow to orange.

Effects of Adding Sodium Hydroxide (NaOH)

The addition of sodium hydroxide (NaOH) will remove H+ ions from the system through the reaction H+ + OH- -> H2O. This decreases the concentration of H+, shifting the equilibrium to the left and making more CrO42-(aq), causing a color change from orange to yellow.

Demonstrating Dynamic Equilibrium

To demonstrate that equilibrium is a dynamic process, an experiment can be conducted by adding a reactant or a product and observing the system's response to maintain equilibrium. For example, adding sulfuric acid to the equilibrium mixture of CrO42-(aq) and Cr2O72-(aq) and observing the color change demonstrates the shifting of equilibrium to counteract the change in concentration.