# GRE Subject Test: Chemistry : Solubility and Precipitation

## Example Questions

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### Example Question #1 : Solubility And Precipitation

Consider the following balanced equation for the solubility of barium hydroxide in an aqueous solution.

What is the solubility of barium hydroxide?

Explanation:

In order to solve for the solubility of barium hydroxide, we need to establish an ICE table for the reaction.

I. Initially, there are no barium ions or hydroxide ions in the solution, so we can call their concentrations zero at the beginning of the reaction.

C. For every molecule of dissolved barium hydroxide, there will be one ion of barium and two ions of hydroxide. As a result, the increases in each ion can be designated  and , respectively.

E. Finally, we plug these values into the equilibrium expression and set it equal to the solubility product constant.

### Example Question #2 : Solubility And Precipitation

Write the solubility product, , for .

Explanation:

The solubility product constant () is an expression that describes the extent to which a compound is soluble in an aqueous solution. It describes the equilibrium between a solid and its constituent ions in a solution. The equilibrium constant for  can be written as:

The denominator represents solid barium sulfate which is considered a constant. When the equation is rearranged, it becomes:

The product, , can be considered a constant expression called the solubility product constant () and the equation can be written in the form:

### Example Question #3 : Solubility And Precipitation

Write the solubility product, , for .

Explanation:

The solubility product constant () is an expression that describes the extent to which a compound is soluble in an aqueous solution. It describes the equilibrium between a solid and its constituent ions in a solution. The equilibrium constant for  can be written as:

The denominator represents solid barium sulfate which is considered a constant. When the equation is rearranged, it becomes:

The product, , can be considered a constant expression called the solubility product constant () and the equation can be written in the form:

### Example Question #4 : Solubility And Precipitation

Write the  expression for the following equilibria:

None of these

Explanation:

The solubility product constant () is an expression that describes the extent to which a compound is soluble in an aqueous solution. It describes the equilibrium between a solid and its constituent ions in a solution.The equilibrium between undissolved  and its ions dissolved in solution is:

The equilibrium constant for  can be written as:

The denominator represents solid barium sulfate which is considered a constant. When the equation is rearranged, it becomes:

The product, , can be considered a constant expression called the solubility product constant () and the equation can be written in the form:

### Example Question #5 : Solubility And Precipitation

Considering that  for the equilibrium reaction:

What would be the  concentration for a solution buffered at a pH of 8.5?

Explanation:

The pH of the solution is , therefore the pOH would be  considering the relationship:

Therefore  based on the equation

The solubility product expression for  is :

By inserting the knowns in to the expression, gives:

Rearrange this equation

### Example Question #6 : Solubility And Precipitation

The Ksp of  is . What is the molar solubility of  in water?

Explanation:

The equation for the dissolution of  in water is below:

The Ksp for the above equation is:

Due to the solubility of  of in water, the concentration of  and - should be equal:

Plug  into the Ksp equation:

Therefore:

The solubility of  in water is

### Example Question #1 : Solubility And Precipitation

The Ksp of  is . What is the molar solubility of  in water?

Explanation:

The equation for the dissolution of  in water is below:

The Ksp for the above equation is:

Due to the solubility of  of in water, the concentration of  and  should be equal:

Plugging X into the Ksp equation gives:

Therefore:

The solubility of CuBr in water is

### Example Question #1 : Solubility And Precipitation

Which salt is insoluble in water?

Explanation:

Solubility rules must be followed for substances in aqueous media. Below are some of the solubility rules and they must be followed in the order given. For example, rule 1 should have precedence over rule 2.

1. All alkali metal  and  compounds are soluble.

2. Nitrate , perchlorate , chlorate, , and acetate  salts are soluble.

3. Silver, lead, and mercury salts are insoluble.

Thus, we see that silver chloride is insoluble due to rule 3.

### Example Question #1 : Analyzing Solids

The  of  is . What is the molar solubility of  in water?

Explanation:

The equation for the dissolution of  in water is:

The  for the above equation is:

Due to the molar ratios of the species of , the concentration of  and  should be equal when dissolved:

Plugging  into the  equation gives:

Therefore, the solubility of   in water is

### Example Question #1 : Solubility And Precipitation

Calculate the molar solubility of  with  if enough  is added to raise the pH of the solution to pH 12.

Explanation:

The equation for the dissolution of  in water is:

The  for the above equation is:

Due to the solubility of  in water, the concentration of  can be set to:

Therefore the concentration of  should be double that of :

The solution was adjusted to pH 12 using , therefore:

Using an ICE table to process the data:

Plugging these variables into the  equation gives:

Therefore, the  equation can be approximated to:

Therefore, the solubility of  in water is .

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