Question

One can obtain a silica garden if: (a) Silicon salts are grown in garden (b) Crystals of coloured cations are added to a strong solution of sodium silicate (c) Silicon tetrafluoride is hydrolysed (d) Sodium silicate solution is heated with base

Short answer

Option (b) is correct: Crystals of colored cations added to sodium silicate solution form a silica garden.

Step-by-step solution

Identify Key Elements

The exercise states different conditions under which one can obtain a silica garden. We need to analyze each option and identify what's common among them.

Analyze Option (a)

Option (a) claims that Silicon salts are grown in a garden. Growing silicon salts in a garden doesn't form a silica garden because it lacks the necessary chemical process involving sodium silicate.

Analyze Option (b)

Option (b) involves adding crystals of colored cations to a strong solution of sodium silicate. This matches the typical method for creating a silica garden, as the metal cations react with the silicate ions to precipitate silicate structures.

Analyze Option (c)

Option (c) suggests that silicon tetrafluoride is hydrolysed. This process generally leads to the formation of silicic acid and HF, not related directly to forming a silica garden.

Analyze Option (d)

Option (d) involves heating sodium silicate solution with a base. This action doesn't provide the necessary conditions or reactants to form a silica garden structure.

Key concepts

Silicon Salts

Silicon salts are a diverse group of chemical compounds that typically arise from the reaction of silicon-containing acids with bases. In nature, silicon salts are found in various forms such as minerals and silicates. They are usually solid at room temperature and commonly used in various industrial applications.

In the context of creating a silica garden, silicon salts refer to substances that involve silicon and can dissociate into their respective ions. However, not all types of silicon salts are suitable for forming a silica garden. The transformation into a silica structure requires the interaction with sodium silicate and certain metal cations. The garden-like structures are not formed merely by placing silicon salts into a garden-like setting, as the chemical transformation does not occur without a proper chemical process.

Sodium Silicate

Sodium silicate, often called waterglass, is a compound composed primarily of sodium and silicate ions. It appears as a crystal or in liquid form and is an essential component in the creation of a silica garden. This compound serves as a medium for forming complex and aesthetically appealing silica structures.

The preparation of a silica garden involves dissolving sodium silicate in water, creating an alkaline solution that facilitates the precipitation of silicates. When metallic salts, particularly those of transition metals, are introduced to this solution, they meet the silicate ions and react to form insoluble silicate compounds. These compounds grow into towering, plant-like formations characteristic of a silica garden. The concentration of sodium silicate plays a crucial role in the appearance and structure of the silica formations, as weak solutions might not sustain the growth needed to form prominent structures.

Chemical Process

The chemical process behind forming a silica garden is fascinating and reveals much about chemical interactions and kinetics. The process involves a series of reactions that take place when crystals of metal cations are added to a concentrated solution of sodium silicate.

When the metal cations contact the silicate-rich solution, they undergo a chemical reaction resulting in the formation of metal silicates. These silicates are often insoluble and precipitate out of the solution, forming solid structures. The initial formations act as a seed for further growth as the surrounding silicate ions continue to react with the metal ions present in the solution.

• This phenomenon follows the principles of osmosis as water moves through the semi-permeable membrane of the silicate structures, causing them to grow.
• The osmosis-driven growth leads to brittle, yet brightly colored formations, which often resemble undersea coral reefs or gardens, hence the name "silica garden."

This chemical magic is sometimes used as an educational demonstration to showcase basic chemical principles such as reaction kinetics, solubility, and the formation of crystal structures.