Question

Identify the false statement regarding the solutions of alkali metals in ammonia. (1) The blue colour, paramagnetic character and reduction properties of the solution are due to ammoniated electrons. (2) The conduetivity is due to both ammoniated electrons and ammoniated metal ions. (3) Evaporation of the solution in the absence of catalyst or impurities gives metal amides. (4) The conductivity of saturated solutions is normally equal to the metal dissolved in ammonia.

Short answer

Statement (3) is false.

Step-by-step solution

Understand the properties of alkali metals in ammonia

Review the properties of alkali metals dissolved in liquid ammonia. This includes understanding their blue color, paramagnetic character, conductance due to ammoniated electrons and ammoniated metal ions, and the chemical reactions occurring during evaporation.

Evaluate each statement

Carefully read each statement and compare it to the known properties from Step 1. Determine if each statement accurately describes the properties.

Identify the false statement

Analyze the validity of each option: (1) True: Blue color, paramagnetic character, and reduction properties are due to ammoniated electrons.(2) True: Conductivity is due to both ammoniated electrons and metal ions.(3) False: Evaporation without impurities generally does not lead to metal amides.(4) True: Conductivity of saturated solutions relates to the dissolved metal.

Key concepts

ammoniated electrons

When alkali metals dissolve in liquid ammonia, they release valence electrons. These free electrons form a solution known as 'ammoniated electrons'. These electrons are responsible for several unique properties of the solution.

The solutions appear blue due to these ammoniated electrons; this blue color is a signature trait of electron presence. The presence of free electrons in the solution gives it a strong reducing ability as well.

Additionally, the electrons floating in the ammonia make the solution paramagnetic, meaning it's attracted to magnetic fields. This is similar to how certain metals like iron behave, but here, it's due to the free electrons in the ammonia.

paramagnetic character

The paramagnetic nature of alkali metals in ammonia is directly tied to the presence of ammoniated electrons. Paramagnetism refers to the material being attracted by an external magnetic field.

Alkali metal solutions in ammonia exhibit paramagnetism primarily because the dissolved free electrons align with external magnetic fields. This behavior is quite different from the metals in their solid state.

Understanding this helps us know why these solutions are used in various magnetic studies and applications, as they respond in specific ways to magnetic fields due to their electron content.

solution conductivity

The electrical conductivity of the solution formed by dissolving alkali metals in ammonia is highly significant. This conductivity stems from two main contributors: ammoniated electrons and ammoniated metal ions.

Ammoniated electrons act as immediate free charge carriers, moving through the solution to conduct electricity.

Ammoniated metal ions also help in carrying charges, especially when the solution gets saturated. These ions interact with the electrons, ensuring the conductivity is quite stable.

Thus, the combined presence of these components makes the solution an excellent conductor of electricity, which is key in various scientific and industrial processes.

chemical reactions of alkali metals

The reaction of alkali metals with ammonia leads to a number of interesting chemical interactions. When an alkali metal dissolves in ammonia, it releases electrons and forms a blue, conductive solution.

Upon evaporation of this solution, different reactions can occur depending on the conditions. Usually, the metal will revert to its solid form.

However, without catalysts or impurities, evaporation typically leads to the pure metal being recovered. If oxygen or other impurities are present, more complicated compounds such as metal amides can form.

The understanding of these reactions helps in predicting the outcomes in various chemical processes involving alkali metals and ammonia.

evaporation properties

Evaporation of alkali metal solutions in ammonia reveals interesting properties. Normally, if you evaporate the ammonia without impurities or catalysts, the dissolved metal will solidify back to its pure form.

Generally, metal amides are not formed in pure conditions. However, the presence of specific impurities or catalysts can lead to the formation of other compounds.

This points to the controlled environment needed to study the accurate properties of these metals and their solutions. Understanding these properties is essential for applications in chemistry and materials science where precise substance behavior is critical.