Question

Which of the following statements are correct? (1) The hybridisation of \(\mathrm{C}\) in graphite is \(\mathrm{sp}^{2}\). (2) \(\mathrm{SiO}_{2}\) reacts with \(\mathrm{Na}_{2} \mathrm{CO}_{3}\) and liberates \(\mathrm{CO}\). (3) \(\mathrm{SiO}_{2}\) is used as acid flux. (4) The distance between the layers in graphite is \(3.35 \times 10-3 \mathrm{~cm}\) (a) 1,2 and 3 (b) 1,2 and 4 (c) 1,3 and 4 (d) 2,3 and 4

Short answer

Correct choices: 1 and 3 only. However, none of the provided options accurately reflect this.

Step-by-step solution

Analyze the Hybridization of Carbon in Graphite

In graphite, each carbon atom is bonded to three other carbon atoms in a planar structure. This involves the formation of three sigma bonds and one pi bond, which corresponds to sp2 hybridization. Therefore, the statement about the hybridization of \(\mathrm{C}\) in graphite is correct. Statement 1 is true.

Evaluate Reaction of SiO2 with Na2CO3

When \(\mathrm{SiO}_{2}\) reacts with \(\mathrm{Na}_{2} \mathrm{CO}_{3}\), it forms \(\mathrm{Na}_{2}\mathrm{SiO}_{3}\) and \(\mathrm{CO}_{2}\) rather than \(\mathrm{CO}\). Thus, Statement 2 is incorrect.

Determine if SiO2 is Used as Acid Flux

\(\mathrm{SiO}_{2}\) is indeed used as an acid flux. It reacts with basic oxides during metallurgical processes to form molten silicates, which suggests that Statement 3 is correct.

Verify the Distance Between Layers in Graphite

The distance between the layers in graphite is approximately \(3.35 \times 10^{-8}\) cm, which does not match the given option of \(3.35 \times 10^{-3}\) cm. Therefore, Statement 4 is incorrect.

Select the Correct Statements

Based on the analysis: Statement 1 is true, Statement 2 is false, Statement 3 is true, and Statement 4 is false. Therefore, the correct statements are 1 and 3, which corresponds to option c (1, 3 and 4), though in reality 4 should not be included as true based on the explanation.

Key concepts

Graphite Structure

Graphite is an intriguing form of carbon known for its layered structure, which contributes to its unique properties. Each carbon atom in graphite forms three sigma bonds with neighboring carbon atoms in a flat, two-dimensional layer. These layers are stacked upon each other and are held together by weak van der Waals forces.
The hybridization of carbon in graphite is \( ext{sp}^2\), meaning it involves three \( ext{sp}^2\) hybrid orbitals forming three bonds and possessing one unhybridized \( ext{p}\) orbital. The unhybridized \( ext{p}\) orbitals overlap to create \( ext{pi}\) bonds, contributing to the overall bonding situation in the graphite layers.
Graphite's layers can easily slide over one another, giving it a slippery feel and making it useful as a lubricant or in pencils. The distance between these layers is crucial in understanding the properties of graphite and is approximately \[3.35 \times 10^{-8}\, \text{cm}\].\ However, this value is often mistakenly reported as larger, which causes confusion.

Reactivity of Silicon Dioxide

Silicon dioxide, or \( ext{SiO}_2\), is a compound with interesting chemical properties, often found in nature as quartz. Its lack of reactivity is due to its robust covalent bonds in a three-dimensional framework, granting it high stability.
Silicon dioxide plays a significant role in industrial processes. One such reaction involves \( ext{Na}_2 ext{CO}_3\) (sodium carbonate), where \( ext{SiO}_2\) reacts to form \( ext{Na}_2 ext{SiO}_3\) (sodium silicate) and \( ext{CO}_2\) (carbon dioxide), not \( ext{CO}\) as sometimes misquoted. The reaction is as follows:
\[ \text{SiO}_2 + \text{Na}_2 ext{CO}_3 \rightarrow \text{Na}_2 ext{SiO}_3 + \text{CO}_2\].
This demonstrates \( ext{SiO}_2\)'s ability to act as an acidic oxide, which is a feature that significantly influences its applications in various fields.

Acid Flux in Metallurgy

In metallurgy, fluxes play a critical role in purifying metals during their extraction or refining. Silicon dioxide \( \text{SiO}_2 \) is frequently used as an acid flux. This is because it can combine with basic oxides, present in metal ores, to form silicates.
An acid flux's role is to facilitate the removal of impurities by forming a liquid slag that can be easily separated from the molten metal. During smelting processes, \(\text{SiO}_2\) aids in binding impurities and aids in the smooth removal of slag from the metal.
This is essential in the production of metals like iron, where excess acidic or basic substances need to be neutralized and removed. Understanding the chemistry involved with \(\text{SiO}_2\) as an acid flux helps metallurgists improve the efficiency and quality of refining processes.