# High School Chemistry : Using Stoichiometry in Solutions

## Example Questions

### Example Question #4 : Precipitates And Calculations

What is the mass of the solid left over after boiling off 100mL of 0.4M NaCl solution?

Explanation:

The remaining mass with be equal to the mass of the sodium chloride in the solution. Once the solvent (water) evaporates, the solute will remain.

Atomic mass of sodium is ~23. Atomic mass of chlorine is ~35.5. Molecular mass of NaCl is ~58.5.

### Example Question #1 : Using Stoichiometry In Solutions

How much water is necessary to make a solution with a molality of  when of sodium chloride are in the solution?

Explanation:

This question is asking us to solve for molality, which has the following equation:

Note how the equation does not ask for liters of solution like molarity, but instead requires the kilograms of solvent used in the solution. By dividing the mass of the sodium chloride by its molar mass, we can solve for the moles of sodium chloride in solution.

This will allow us to solve for the mass of water used in the solution.

This gives us the mass of water required to make the solution.

### Example Question #2 : Limiting Reagent

Consider the reaction of potassium carbonate with calcium nitrate to form potassium nitrate and calcium carbonate:

Suppose 50ml of a 0.250M potassium carbonate solution was mixed with 100ml of a 0.175M calcium nitrate solution. What is the maximum amount of calcium carbonate that could be obtained?