Question

Silica is soluble in: (a) HF (b) \(\mathrm{HNO}_{3}\) (c) \(\mathrm{H}_{2} \mathrm{SO}_{4}\) (d) \(\mathrm{HCl}\)

Short answer

Silica is soluble in HF (option a).

Step-by-step solution

Introduction to Problem

The question asks us to identify which of the given substances silica is soluble in from the provided options: (a) HF, (b) \(\mathrm{HNO}_{3}\), (c) \(\mathrm{H}_{2} \mathrm{SO}_{4}\), and (d) \(\mathrm{HCl}\). To solve this, we will examine the properties of the reactions between silica and each substance.

Analyze Solubility of Silica in HF

Silica, \(\mathrm{SiO}_{2}\), reacts with hydrofluoric acid (HF) to form hexafluorosilicic acid \((\mathrm{H}_{2}\mathrm{SiF}_{6})\) and water. The reaction is: \[\mathrm{SiO}_{2} + 6\mathrm{HF} \rightarrow \mathrm{H}_{2}\mathrm{SiF}_{6} + 2\mathrm{H}_{2}\mathrm{O}.\]This reaction confirms that silica is soluble in hydrofluoric acid.

Evaluate Interaction with \(\mathrm{HNO}_{3}\)

Silica is generally resistant to reactions with nitric acid \((\mathrm{HNO}_{3})\). This means it does not dissolve or react significantly with \(\mathrm{HNO}_{3}\), thus it remains insoluble in it.

Check Solubility in \(\mathrm{H}_{2}\mathrm{SO}_{4}\)

Silica is also resistant to sulfuric acid \((\mathrm{H}_{2}\mathrm{SO}_{4})\). It does not dissolve in \(\mathrm{H}_{2}\mathrm{SO}_{4}\), so it remains insoluble without significant reaction occurring.

Determine Reaction with \(\mathrm{HCl}\)

Silica does not react with hydrochloric acid \((\mathrm{HCl})\) under typical conditions. It is insoluble in \(\mathrm{HCl}\), showing strong chemical inertness.

Key concepts

SiO2 reactions

Silica, known chemically as \(\text{SiO}_2\), is an interesting compound due to its interactions, or the lack thereof, with various substances. Understanding its reactivity is key to understanding where it can dissolve and where it remains inert. In the context of acids typically found in a chemical laboratory, silica shows a specific kind of selectivity:

• It reacts with hydrofluoric acid (HF).
• It resists dissolution in nitric acid (\(\text{HNO}_3\)), sulfuric acid (\(\text{H}_2\text{SO}_4\)), and hydrochloric acid (\(\text{HCl}\)).

Silica's reactivity or lack thereof is highly dependent on the chemical nature of the acid it encounters.

hydrofluoric acid

Hydrofluoric acid (HF) is a unique acid when it comes to reacting with silica (\(\text{SiO}_2\)). Unlike other strong acids, HF has the ability to dissolve silica. This dissolution occurs due to the specific chemical interaction between HF and \(\text{SiO}_2\), forming hexafluorosilicic acid \((\text{H}_2\text{SiF}_6)\) and water as products: \[\text{SiO}_2 + 6\text{HF} \rightarrow \text{H}_2\text{SiF}_6 + 2\text{H}_2\text{O}\]This reaction highlights the unique reactivity of HF, making it the only common acid capable of breaking down and dissolving silica, demonstrating its crucial industrial applications and potential hazards.

chemical inertness

Chemical inertness refers to a substance's resistance to chemical reactions. Silica is especially renowned for its chemical inertness when in contact with most acids, which is important for its stability in various environments. Despite being a solid substance, silica's chemical structure provides it with superior resilience, preventing dissolution in acids such as:

• Nitric acid \((\text{HNO}_3)\)
• Sulfuric acid \((\text{H}_2\text{SO}_4)\)
• Hydrochloric acid \((\text{HCl}\))

This characteristic makes silica a useful component in applications requiring materials that do not easily degrade or react.

acid-solubility of silicates

The acid-solubility of silicates like silica is mostly dependent on the type of acid they encounter. While silica's interaction with hydrofluoric acid showcases its solubility, it typically resists most other common acids due to its strong silicon-oxygen bonds. This leads to:

• Solubility in HF due to the formation of \(\text{H}_2\text{SiF}_6\).
• Insolubility in stronger acids like \(\text{HNO}_3\), \(\text{H}_2\text{SO}_4\), and \(\text{HCl}\) under normal conditions.

Each acid interacts differently with silicates, not only dependent on the acid's strength but also on its ability to disrupt the chemical bonds within the silicate structure.