Problem 53 - Chemistry and Chemical Reactivity

Question

Elemental silicon is oxidized by \(\mathrm{O}_{2}\) to give unknown A. Compound \(A\) is dissolved in molten \(\mathrm{Na}_{2} \mathrm{CO}_{3}\) giving \(\mathrm{B}\). When \(\mathrm{B}\) was treated with aqueous hydrochloric acid, \(\mathrm{C}\) is produced. Identify compound C. (a) \(\mathrm{SiH}_{4}\) (b) \(\mathrm{H}_{4} \mathrm{SiO}_{4}\) (c) \(\mathrm{SiO}_{2}\) (d) \(\operatorname{sicl}_{4}\)

Step-by-Step Solution

Answer

The correct answer is (b) \( \mathrm{H}_{4} \mathrm{SiO}_{4} \).

Step 1: Oxidation of Silicon

Elemental silicon (Si) is oxidized by oxygen (\( \mathrm{O}_2 \)) to form silicon dioxide \( \mathrm{SiO}_2 \), which we'll call Compound A. The reaction is:\[ \mathrm{Si} + \mathrm{O}_2 \rightarrow \mathrm{SiO}_2 \]

Step 2: Reaction with Sodium Carbonate

Compound A (\( \mathrm{SiO}_2 \)) is dissolved in molten sodium carbonate \( \mathrm{Na}_2 \mathrm{CO}_3 \) to form sodium silicate \( \mathrm{Na}_2\mathrm{SiO}_3 \), which we'll call Compound B.The reaction is:\[ \mathrm{SiO}_2 + \mathrm{Na}_2 \mathrm{CO}_3 \rightarrow \mathrm{Na}_2\mathrm{SiO}_3 + \mathrm{CO}_2 \]

Step 3: Reaction with Hydrochloric Acid

Compound B (\( \mathrm{Na}_2\mathrm{SiO}_3 \)) is treated with aqueous hydrochloric acid \( \mathrm{HCl} \), producing silicic acid \( \mathrm{H}_4\mathrm{SiO}_4 \), which we'll call Compound C.The reaction is:\[ \mathrm{Na}_2\mathrm{SiO}_3 + 2\mathrm{HCl} + 2\mathrm{H_2O} \rightarrow \mathrm{H}_4\mathrm{SiO}_4 + 2\mathrm{NaCl} \]

Step 4: Identify Compound C

Based on the reaction with \( \mathrm{HCl} \), Compound C is silicic acid \( \mathrm{H}_4\mathrm{SiO}_4 \). The correct answer is:(b) \( \mathrm{H}_{4} \mathrm{SiO}_{4} \).

Key Concepts

Oxidation of Silicon

Silicon is a chemical element with the symbol Si. It's a hard and brittle crystalline solid frequently used in electronics. When elemental silicon is subjected to oxygen, a chemical reaction called oxidation occurs. This transformation results in the formation of silicon dioxide, also known as silica. The process can be seen in the equation:

• \( \mathrm{Si} + \mathrm{O}_2 \rightarrow \mathrm{SiO}_2 \)

This oxidation process is vital as silicon dioxide serves as an essential component in various industrial applications. For instance, it is a critical material in glass manufacturing and ceramics. By understanding how silicon reacts with oxygen, we can harness its properties in technological advancements.

Sodium Silicate Formation

Silicon dioxide, generated from the oxidation of silicon, can interact with sodium carbonate under high-temperature conditions. This reaction forms sodium silicate, a compound often referred to as "water glass." The formation reaction is as follows:

• \( \mathrm{SiO}_2 + \mathrm{Na}_2 \mathrm{CO}_3 \rightarrow \mathrm{Na}_2\mathrm{SiO}_3 + \mathrm{CO}_2 \)

Sodium silicate has numerous practical applications. It is utilized in detergents, adhesives, and even as a binding agent in the construction industry. This compound's diverse uses are due to its ability to form a glassy structure when dissolved in water, which makes it particularly valuable in coating processes and as a fire protection solution.

Chemical Reactions with Hydrochloric Acid

Sodium silicate, when treated with aqueous hydrochloric acid, undergoes a fascinating chemical transformation. The interaction leads to the production of silicic acid, alongside the by-product sodium chloride (table salt). The reaction can be expressed as:

• \( \mathrm{Na}_2\mathrm{SiO}_3 + 2\mathrm{HCl} + 2\mathrm{H_2O} \rightarrow \mathrm{H}_4\mathrm{SiO}_4 + 2\mathrm{NaCl} \)

Silicic acid, \( \mathrm{H}_4\mathrm{SiO}_4 \), is an important compound in various chemical processes and serves as a precursor to other silicon-based materials. This reaction illustrates just one way chemical interactions modify substances, highlighting the broader principle of chemical synthesis. Understanding these reactions offers insight into industrial chemistry and how raw materials are transformed into valuable products.