Question

Silicon is produced for the chemical and electronics industries by the following reactions. Give the balanced equation for each reaction. a. \(\mathrm{SiO}_{2}(s)+\mathrm{C}(s) \frac{\text { Electic }}{\text { arc furmae }} \mathrm{Si}(s)+\mathrm{CO}(g)\) b. Liquid silicon tetrachloride is reacted with very pure solid magnesium, producing solid silicon and solid magnesium chloride. c. \(\mathrm{Na}_{2} \mathrm{SiF}_{6}(s)+\mathrm{Na}(s) \rightarrow \operatorname{Si}(s)+\operatorname{NaF}(s)\)

Short answer

The balanced equations for the given reactions are: a. \(\mathrm{SiO}_{2}(s) + \mathrm{2C}(s) \rightarrow \mathrm{Si}(s) + \mathrm{2CO}(g)\) b. \(\mathrm{SiCl}_{4}(l) + \mathrm{Mg}(s) \rightarrow \mathrm{Si}(s) + \mathrm{MgCl}_{2}(s)\) c. \(\mathrm{Na}_{2} \mathrm{SiF}_{6}(s) + \mathrm{6Na}(s) \rightarrow \mathrm{Si}(s) + \mathrm{6NaF}(s) \)

Step-by-step solution

Write the unbalanced equation

The unbalanced equation for this reaction is: \(\mathrm{SiO}_{2}(s) + \mathrm{C}(s) \rightarrow \mathrm{Si}(s) + \mathrm{CO}(g)\)

Balance the equation

To balance this equation, we need to ensure that the number of atoms of each element is the same on both the reactants and products side. From the unbalanced equation, we can balance the equation by adding one carbon (C) atom: \(\mathrm{SiO}_{2}(s) + \mathrm{2C}(s) \rightarrow \mathrm{Si}(s) + \mathrm{2CO}(g)\) Now, the balanced equation for the reaction is: \(\mathrm{SiO}_{2}(s) + \mathrm{2C}(s) \rightarrow \mathrm{Si}(s) + \mathrm{2CO}(g)\) b. Reaction between liquid silicon tetrachloride and solid magnesium:

Write the unbalanced equation

This reaction can be written as: \(\mathrm{SiCl}_{4}(l) + \mathrm{Mg}(s) \rightarrow \mathrm{Si}(s) + \mathrm{MgCl}_{2}(s)\)

Balance the equation

To balance this equation, we need to ensure that the number of atoms of each element is the same on both the reactants and products side. In this case, one silicon, four chlorine, and one magnesium atom are present on both sides, so the equation is already balanced: \(\mathrm{SiCl}_{4}(l) + \mathrm{Mg}(s) \rightarrow \mathrm{Si}(s) + \mathrm{MgCl}_{2}(s)\) c. Reaction between Sodium Fluorosilicate (Na₂SiF₆) and Sodium (Na):

Write the unbalanced equation

This reaction can be written as: \(\mathrm{Na}_{2} \mathrm{SiF}_{6}(s) + \mathrm{Na}(s) \rightarrow \mathrm{Si}(s) + \mathrm{NaF}(s)\)

Balance the equation

To balance this equation, we need to ensure that the number of atoms of each element is the same on both the reactants and products side. We can balance this equation by adding six sodium (Na) atoms and six fluoride (F) atoms: \(\mathrm{Na}_{2} \mathrm{SiF}_{6}(s) + \mathrm{6Na}(s) \rightarrow \mathrm{Si}(s) + \mathrm{6NaF}(s)\) Now, the balanced equation for the reaction is: \(\mathrm{Na}_{2} \mathrm{SiF}_{6}(s) + \mathrm{6Na}(s) \rightarrow \mathrm{Si}(s) + \mathrm{6NaF}(s)\)

Key concepts

Stoichiometry

Stoichiometry is the branch of chemistry that deals with the quantitative relationships between reactants and products in a chemical reaction. In simpler terms, it tells us how much of each substance is needed or produced in a reaction.

Understanding stoichiometry is crucial when balancing chemical equations. It allows us to predict and calculate the quantities of substances consumed and produced. For instance, in the silicon production example featuring the reaction of silicon dioxide and carbon to produce silicon and carbon monoxide, stoichiometry helps us determine that two moles of carbon are needed to produce two moles of carbon monoxide from one mole of silicon dioxide.

When applying stoichiometry, we must consider the Law of Conservation of Mass, which states that mass cannot be created or destroyed in an ordinary chemical reaction. This law is the principle behind the balancing of equations, ensuring that the number of atoms for each element is the same on both sides of the equation.

Chemical Reactions

Chemical reactions are processes where reactants are transformed into products through the breaking and forming of chemical bonds. There are various types of reactions, each with its own set of rules for how reactants interact and result in products.

In the context of silicon production, chemical reactions are utilized to refine and produce pure silicon. For example, the first reaction given involves an electric arc furnace to reduce silicon dioxide to silicon. This process is a type of reduction reaction where carbon is the reducing agent. In the second reaction, silicon tetrachloride is reacted with magnesium, and it highlights a single replacement reaction where magnesium replaces the silicon in silicon tetrachloride.

Balancing these reactions is vital to determine the exact amounts of reactants needed and to predict the amount of product formed. It further helps in understanding the process energetics and kinetics, which are essential for industrial applications.

Silicon Production Chemistry

The chemistry involved in producing silicon is intricate and requires high-purity materials and precise reactions. Silicon is used extensively in the electronics industry, particularly for making semiconductors.

In the provided exercise, various methods of producing silicon are described. The reactions are part of an industrial process that includes the reaction of high-purity silicon dioxide with carbon at high temperatures to reduce it to silicon, using a very intense electric arc. In another method, a more purified form of silicon is obtained by reacting silicon tetrachloride with magnesium. Here, ultra-pure solid magnesium is used to ensure that no impurities are introduced into the silicon product.

Each of these methods has been developed to optimize the yield and purity of the final silicon product. Understanding the chemical reactions and stoichiometry involved in each step of the production process is essential to enhance efficiency and reduce costs while maintaining the quality of the silicon produced for various applications.