S4E2 - Strong and Weak Electrolytes, Nonelectrolytes, and Molarity

SECTION 4 - Types of Chemical Reactions and Solution Stoichiometry

At the end of my first post on SECTION 4 - Types of Chemical Reactions and Solution Stoichiometry, we introduced Strong Electrolytes, Weak Electrolytes, and Nonelectrolytes.

Let's elaborate on each of these 3 types of substances...

1. Strong Electrolytes.

Strong Electrolytes = substances (solutes) that are completely ionized (hydrated) when dissolved in water.

  ex:  very soluble salts (i.e. NaCl)
  ex:  strong acids (i.e. HCl, HNO3, HClO4, H2SO4)
  ex:  strong bases (i.e. NaOH, KOH)

➞ when the above compounds are dissolved in water, they are 100% ionized. In other words, they ionize (dissociate into cation and anion) completely:

Strong Electrolytes Conduct Electricity

So, the easier it is for a substance (solute) to form ions in solution, the better it is at conducting electricity because ions act as charge carriers in aqueous solutions.


2. Weak Electrolytes.

Weak Electrolytes = substances that ionize (dissolve) only slightly in water.

➞ two most common are:  NH3 (ammonia) and HC2H3O2 (acetic acid).

➞ they produce relatively few ions (charge carriers) when dissolved...

Weak Electrolytes Dissociate to a Slight Extent

See the reaction arrow above?  It shows us that mainly only HC2H3O2 is present and it's not an ion.

Because acetic acid (HC2H3O2) is a weak electrolyte, it's called a weak acid.

weak acid = any acid that dissociates (ionizes) only to a slight extent in aqueous solution.


ex:  The most common weak base is ammonia (NH3). It's a weak electrolyte:

Ammonia is a Weak Electrolyte

The solution is basic because OH- ions are produced. But because very few OH- ions are formed, NH3 is a weak electrolyte, and thus a weak base.


3. Nonelectrolytes.

Nonelectrolytes = substances that do dissolve in water to make an aqueous solution, but do not produce any ions.

  ex:  C2H5OH (ethanol)
  ex:  C12H22O11 (sucrose) -- table sugar. Here's what happens:

Sucrose is a Nonelectrolyte


Molarity and Concentration in Chemistry.

The extent to which a solute dissolves in a solution is expressed by the solution's concentration.

Concentration is most often expressed as molarity (M).

Molarity (M)  =  number of moles of solute (mol)  /  liters of solution (L).

   So, 1M  =  1 mol/L.

   Here it is again, but easier to follow:

The Molarity Formula

Molarity Calculations.

ex:  Calculate the molarity of a solution made by dissolving 11.5g of solid NaOH in enough water to make 1.50L of solution.

- well, we know that molarity = moles of NaOH / liters of solution.

- we already have the "liters of solution" = 1.50L

- so the first thing we need to do, is calculate the "moles of NaOH"...

 Molarity Calculation Example


In my next video blog post from this series: SECTION 4 - Types of Chemical Reactions and Solution Stoichiometry, we'll cover more Molarity Calculations.