Question

Although pure \(\mathrm{NaOH}\) and \(\mathrm{NH}_{3}\) have very different properties, their aqueous solutions possess many common properties. List some general properties of these solutions, and explain their common behavior in terms of the species present.

Short answer

Aqueous solutions of NaOH and NH3 possess some common properties, like bitter taste, slippery feel, color change of indicators, neutralization of acids, electrical conductivity, and reaction with certain metals. This common behavior can be attributed to the presence of hydroxide ions (OH-) in both solutions. The hydroxide ions are responsible for these basic properties as they can accept protons from other molecules or donate electrons to form a bond with a hydrogen ion.

Step-by-step solution

List general properties of NaOH and NH3 solutions.

Both NaOH and NH3 are examples of bases, so their aqueous solutions have some common properties: 1. They taste bitter 2. They feel slippery or soapy to touch 3. They can change the color of some indicators (e.g., turn red litmus paper to blue) 4. They can neutralize acids 5. They can conduct electricity 6. They react with certain metals to produce hydrogen gas

Describe species present in NaOH and NH3 solutions.

In an aqueous solution of NaOH, the hydroxide \(\mathrm{(OH^{-})}\) ion is present. The chemical equation for the dissociation of NaOH in water is: \[ \mathrm{NaOH \rightarrow Na^{+}(aq) + OH^{-}(aq)} \] In an aqueous solution of NH3, the formation of ammonium \(\mathrm{(NH_{4}^{+})}\) ions and hydroxide \(\mathrm{(OH^{-})}\) ions occurs. The chemical equation for the dissolution of NH3 in water is: \[ \mathrm{NH_{3}(aq) + H_{2}O(l) \rightleftharpoons NH_{4}^{+}(aq) + OH^{-}(aq)} \] The common species in both the solutions is the hydroxide ion \(\mathrm{(OH^{-})}\).

Explain common behavior in terms of species present.

The common properties of these solutions can be explained by the presence of hydroxide ions (OH-) in both solutions. The hydroxide ions are responsible for the basic properties as they can accept protons from other molecules or donate electrons to form a bond with a hydrogen ion: 1. The bitter taste is due to the reaction of hydroxide ions with the taste receptor cells on the tongue. 2. The slippery or soapy feeling is the result of a saponification reaction between the hydroxide ions and the fats or oils present on the skin. 3. The color change of indicators, such as litmus paper, is due to the reaction between hydroxide ions and the weak acids present in the indicator. 4. The neutralization of acids occurs because the hydroxide ions can react with hydrogen ions (from acids) to form water. 5. The electrical conductivity is due to the presence of charged ions (Na+, OH-, NH4+, and OH-) in solution, which can move under the influence of an electric field. 6. Reaction with metals (like zinc or aluminum) to produce hydrogen gas occurs as a result of the hydroxide ions reacting with the metal to form a metal hydroxide and release hydrogen gas. Hence, the common behavior of NaOH and NH3 solutions can be attributed to the presence of hydroxide ions in both solutions.