Chemical Equilibrium: Observing Changes in Cr2O7- & CrO4- Mixture

In summary, when potassium chromate is dissolved in acid, there is an equilibrium between chromate ion and dichromate ion. The net ionic equation for this reaction is 2 CrO4^2- (aq) + 2 H3O^+ (equilibrium symbol) Cr2O7^2- (aq) + 3 H2O (l). A student studying this equilibrium will observe a light orange color in the equilibrium mixture. When a solution of H2SO4 is added to this mixture at equilibrium, the student will observe a change in color. The explanation for this is that the addition of H2SO4 will shift the equilibrium towards the formation of more dichromate ion, which is a
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an equilibrium exists between chromate ion and the dichromate ion when potassium chromate is dissolved acid. the net ionic equation describing this reaction is given in the follwering equation:

2 CrO4^2- (aq) + 2 H3O^+ (equilibrium symbol) Cr2O7^2- (aq) + 3 H2O (l)

a student studying this equilibrium begins w/ an equilibrium mixture that is light orage in color.

a. what change will the student observe when a solution of H2SO4 is added to this mixture at equilibrium?

b. briefly explain the above answer

c. what change will the student observe when a solution of NaOH is added to another example of this solution at equilibrum. why?
 
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a. The student will observe a color change from light orange to dark red.

b. This color change is due to the shift in equilibrium towards the formation of more dichromate ions (Cr2O7^2-). When H2SO4 is added, it acts as a strong acid and increases the concentration of H3O+ ions in the solution. According to Le Chatelier's principle, this increase in H3O+ ions will shift the equilibrium towards the side with fewer H3O+ ions, which in this case is the formation of more dichromate ions. Since dichromate ions are dark red in color, the overall color of the solution will appear darker.

c. When a solution of NaOH is added to another example of this solution at equilibrium, the student will observe a color change from light orange to yellow. This is because NaOH is a strong base and will increase the concentration of OH- ions in the solution. This increase in OH- ions will shift the equilibrium towards the side with fewer OH- ions, which in this case is the formation of more chromate ions (CrO4^2-). Since chromate ions are yellow in color, the overall color of the solution will appear more yellow.
 

1. What is chemical equilibrium?

Chemical equilibrium is a state in a chemical reaction where the forward and reverse reactions occur at the same rate, resulting in no net change in the concentrations of reactants and products.

2. How do you observe changes in a Cr2O7- & CrO4- mixture?

Changes in a Cr2O7- & CrO4- mixture can be observed through color changes. When the two ions are mixed together, the orange dichromate ion (Cr2O7-) will react with water to form the yellow chromate ion (CrO4-), resulting in a change in color from orange to yellow.

3. What factors affect chemical equilibrium?

The factors that affect chemical equilibrium include temperature, pressure, concentration of reactants and products, and the presence of a catalyst. Changes in any of these factors can shift the equilibrium in favor of the forward or reverse reaction.

4. What is Le Chatelier's principle?

Le Chatelier's principle states that when a stress is applied to a system at equilibrium, the system will respond by shifting in the direction that reduces the stress. This means that if a change is made to a system at equilibrium, the equilibrium will shift to counteract that change.

5. How do you calculate the equilibrium constant for a chemical reaction?

The equilibrium constant, denoted by K, is calculated by taking the ratio of the concentrations of the products to the concentrations of the reactants, each raised to their respective stoichiometric coefficients. K = [products] / [reactants]. The specific form of the equilibrium constant equation depends on the balanced chemical equation for the reaction.

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