Question

Classify each solute represented in the following equations as a strong, weak, or nonelectrolyte: a. \(\mathrm{K}_{2} \mathrm{SO}_{4}(s) \stackrel{\mathrm{H}_{2} \mathrm{O}}{\longrightarrow} 2 \mathrm{~K}^{+}(a q)+\mathrm{SO}_{4}^{2-}(a q)\) \mathbf{b} . ~ \(\mathrm{NH}_{4} \mathrm{OH}(a q) \stackrel{\mathrm{H}_{2} \mathrm{O}}{\rightleftarrows} \mathrm{NH}_{4}^{+}(a q)+\mathrm{OH}^{-}(a q)\) c. \(\mathrm{C}_{6} \mathrm{H}_{12} \mathrm{O}_{6}(s) \stackrel{\mathrm{H}_{2} \mathrm{O}}{\longrightarrow} \mathrm{C}_{6} \mathrm{H}_{12} \mathrm{O}_{6}(a q)\)

Short answer

a. Strong electrolyte; b. Weak electrolyte; c. Nonelectrolyte.

Step-by-step solution

Analyze the equation for \(\text{K}_{2}\text{SO}_{4}\)

Examine the equation: \(\text{K}_{2}\text{SO}_{4}(s) \rightarrow 2 \text{K}^{+}(aq) + \text{SO}_{4}^{2-}(aq)\). Potassium sulfate (\(\text{K}_{2}\text{SO}_{4}\)) dissociates completely into its ions in water, hence, it is a strong electrolyte.

Analyze the equation for \(\text{NH}_{4}\text{OH}\)

Examine the equation: \(\text{NH}_{4}\text{OH}(aq) \rightleftharpoons \text{NH}_{4}^{+}(aq) + \text{OH}^{-}(aq)\). Ammonium hydroxide (\(\text{NH}_{4}\text{OH}\)) partially dissociates in water, indicated by the double arrow. Therefore, it is a weak electrolyte.

Analyze the equation for \(\text{C}_{6}\text{H}_{12}\text{O}_{6}\)

Examine the equation: \(\text{C}_{6}\text{H}_{12}\text{O}_{6}(s) \rightarrow \text{C}_{6}\text{H}_{12}\text{O}_{6}(aq)\). Glucose (\(\text{C}_{6}\text{H}_{12}\text{O}_{6}\)) dissolves in water but does not produce ions, so it is a nonelectrolyte.

Key concepts

Strong Electrolytes

Strong electrolytes are substances that completely dissociate into ions when dissolved in water. This means that they conduct electricity very efficiently in aqueous solutions. A common example of a strong electrolyte is potassium sulfate (K2SO4). When K2SO4 is dissolved in water, it separates into potassium ions (K+) and sulfate ions (SO4^2-).
The equation for the dissociation is:
K2SO4(s) → 2 K+(aq) + SO4^2-(aq).
Because the dissociation is complete, strong electrolytes are excellent conductors of electricity in solution.
Other examples include:

• Sodium chloride (NaCl)
• Hydrochloric acid (HCl)
• Sodium hydroxide (NaOH)

Weak Electrolytes

Weak electrolytes only partially dissociate into ions when dissolved in water. This partial dissociation means they conduct electricity, but not as efficiently as strong electrolytes. Ammonium hydroxide (NH4OH) is an example of a weak electrolyte.
The equation for this partial dissociation is:
NH4OH(aq) ⇌ NH4+(aq) + OH-(aq).
The double arrow indicates that the dissociation is reversible and only a fraction of NH4OH molecules ionize at any given time.
Examples of other weak electrolytes include:

• Acetic acid (CH3COOH)
• Phosphoric acid (H3PO4)
• Ammonia (NH3)

Nonelectrolytes

Nonelectrolytes are substances that do not dissociate into ions in water. As a result, they do not conduct electricity in their aqueous solutions. Glucose (C6H12O6) serves as a classic example of a nonelectrolyte.
The equation describing its solubility in water is:
C6H12O6(s) → C6H12O6(aq).
Here, glucose dissolves in water but maintains its molecular structure, meaning no ions are produced. Because no ions are available to carry the electric current, nonelectrolytes are non-conductive.
Other examples include:

• Sucrose (table sugar, C12H22O11)
• Urea (CO(NH2)2)
• Ethanol (C2H5OH)