Solubility and Molarity

Solubility and Molarity

Precipitation of ionic solids

Sometimes, cations and anions combine and come out of the solution as a solid. This solid is called the precipitate, though precipitation are not limited to solids.

Precipitate: a solid formed in a chemical reaction between two solutions

Solubility:

Solubility is the degree of which a compound dissolves in water. Ionic substances vary significantly in solubility, as some solids are more soluble than others. When a compound reaches the limits of its solubility, undissolved solid is visible.

Important Terms:

Solution: a mixture of two or more substances that is uniform throughout.
Solute: substance dissolved in a solution (the stuff being dissolved)
Solvent: substance in which the solute dissolves in a solution (the stuff doing the dissolving)

Solution Concentration:

The concentration of a solution is a measure of the amount of solute that is dissolved in a given amount of solvent. THis is called the molarity d a solution and is expressed in moles per liter, mol/L

Molarity (M) = moles of solute/liters of solution

If you want to make a solution more concentrated you need to add solute, and if you want to make a solution more dilute, or less concentrated, you should add water, or the solvent

A solution is saturated when it can hold not more solute. The solution contains the maximum amount of solute for the given amount of solvent

If you know the molarity of a solution and the size of the sample, you can calculate the number of grams of substance dissolved in that solution: grams = moles x molar mass

You can also use the "magic triangle":

                   mols of solute (mol)

Molarity (M)          Liters of solution (L)

• M= mols/Liters
• mols = Molarity x Liters
• Liters = mols/Molarity

***Molarity is always is units of mol/L, never mol/mL