Safety and Pre-Lab: Equilibrium Pre-Lab Assignment: Consider the following equil
ID: 1087011 • Letter: S
Question
Safety and Pre-Lab: Equilibrium
Pre-Lab Assignment: Consider the following equilibrium system: Chromate and hydronium ions in equilibrium with dichromate and water
Key Question #1:
Write a balanced net ionic equation that describes this equilibrium.
Key Question #2:
Using the Handbook of Chemistry and Physics, look up the physical properties of potassium chromate and potassium dichromate. What observation could you make to determine which of the two species is predominant in a solution?
Key Question #3:
If you add additional acid to the equilibrium system above, in what direction do you predict the equilibrium will shift? What would you observe? Explain why this happens using the balanced net ionic equation from above.
Key Question #4:
If you remove acid from the equilibrium system, in which direction will the reaction shift? What would you observe? Explain why this happens using the balanced net ionic equation from above.
Key Question #5:
How could you remove acid from the equilibrium system? Write a balanced net ionic equation showing how this will remove acid from the system.
Key Question #6:
Given the following information, write a balanced net ionic equation and use it to describe how to remove chromate ion from the equilibrium system. Barium and chromate ions react to form solid barium chromate
Explanation / Answer
2CrO4 2- (aq) + 2H+ (aq) <-----> Cr2O7 2- (aq) + H2O(l)
Chromate ion is predominent in alkaline solution and Dichromate is predominent in acidic solution. It is depends upon the pH of the solutions.
If you add acid then concentration of H+ ions increses so the concentration of reactants increases hence the equilibrium shifts towards right or in forward direction.
If we remove acid from the reaction mixture then theconcentration of H+ ions decreses and products concentration increses hence the equilibrium shifts to left hand side of bakward reaction is favourable.
By adding OH- ions to the system then they convert as water and acid will be removed.
2CrO4 2- + 2H+ + 2 OH- (aq) <------> CrO4 2- (aq) + 2H2O
Ba+2 (aq) + CrO4 2- (aq) -------> BaCrO4 (s)
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