# How Would You Precipitate BaCrO4 from Ba(NO3)2 and K2Cr2O7 Solutions?

• Paulham
In summary, the conversation is about how to precipitate BaCrO4 from a solution of Ba(NO3)2 and K2Cr2O7 using chemical equations. The participants discuss the necessary concentration of CrO42- and how to achieve it by manipulating the concentration of H+. The conclusion is that by adding NaOH to lower the concentration of H+, the equilibrium will shift to the left and form more CrO42-, allowing for the precipitation of BaCrO4 from the solution.
Paulham

## Homework Statement

Hi everyone,

I'm trying to finish my lab report but I'm stuck on this question and don't even know how to start it. Could anyone let me know how to board it or a starting clue?

I'm given these two equations

1. BaCrO4 (s) <---> Ba2+ (aq) + CrO42- (aq)

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

Question: How would you precipitate BaCrO4 from a solution of Ba(NO3)2 and K2Cr2O7 ? And I need to show it in chemical equations.

## The Attempt at a Solution

I honestly have no clue...

You're working on the chromate-dichromate equilibrium in another thread; can you apply that equilibrium to this problem?

Sure, if I knew how to that is...:)

Do you need low, or high concentration of CrO42- to precipitate BaCrO4?

How does concentration of CrO42- depend on pH? (That's a direct conclusion of the question you posted in another thread, changing pH shifts the CrO42-/Cr2O72- equilibrium; how?)

Hi,

I was just looking at that and this is what I came up with: so I would need a high concentration of CrO42- to precipitate BaCrO4 and I can increase the concentration of CrO42- by lowering the concentration of H+ by adding NaOH so it will neutralize the H+. This way my equilibrium will shift to the left forming more CrO42-. Then by adding Ba(NO3)2...the NO3 would be a spectator ion but Ba2+ would form the BaCrO4 precipitate because BaCr2O7 is more soluble...would that be right?

Paulham said:
...would that be right?
It would.

## 1. What is chemical equilibrium?

Chemical equilibrium is a state in a chemical reaction where the rate of the forward reaction is equal to the rate of the reverse reaction. This means that the concentrations of reactants and products remain constant over time.

## 2. How is chemical equilibrium of BaCrO4 achieved?

The chemical equilibrium of BaCrO4 is achieved when the concentration of Ba2+ and CrO42- ions become constant. This can be achieved by either adding the ions in the correct stoichiometric ratio or by allowing the reaction to proceed until equilibrium is reached.

## 3. What factors can affect the chemical equilibrium of BaCrO4?

The factors that can affect the chemical equilibrium of BaCrO4 include temperature, pressure, and concentrations of reactants and products. Changes in any of these factors can shift the equilibrium position and affect the concentrations of the ions.

## 4. How can the Le Chatelier's principle be applied to chemical equilibrium of BaCrO4?

According to the Le Chatelier's principle, when a stress is applied to a system at equilibrium, the system will shift in a way to counteract the stress and reach a new equilibrium. This principle can be applied to the chemical equilibrium of BaCrO4 by predicting how changes in temperature, pressure, or concentrations will affect the equilibrium position and concentrations of ions.

## 5. What is the significance of the chemical equilibrium of BaCrO4?

The chemical equilibrium of BaCrO4 is important in various industrial processes, such as in the production of pigments and ceramics. It is also used in analytical chemistry for quantitative analysis of Ba2+ ions. Understanding the equilibrium of BaCrO4 can also provide insights into other chemical equilibria and reaction mechanisms.

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