S4E2 - Strong and Weak Electrolytes, Nonelectrolytes, and Molarity

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:

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.

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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...

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.

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

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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:

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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:

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"...

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