Question

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

Short answer

The short version of the balanced equations are: a. \( SiO_2(s) + C(s) \rightarrow Si(s) + CO(g) \) b. \( SiCl_4(l) + 2Mg(s) \rightarrow Si(s) + 2MgCl_2(s) \) c. \( 2Na_2SiF_6(s) + 4Na(s) \rightarrow Si(s) + 12NaF(s) \)

Step-by-step solution

Balancing Reaction (a)

Reaction (a): SiO2(s) + C(s) → Si(s) + CO(g) This reaction is already balanced. Each of the reactants and products has one Si atom, two O atoms, and one C atom.

Balancing Reaction (b)

Reaction (b): SiCl4(l) + Mg(s) → Si(s) + MgCl2(s) We have 4 Cl atoms on the reactant side and only 2 Cl atoms on the product side. To balance the Cl atoms, we can adjust the coefficients in the chemical equation. The balanced equation is: SiCl4(l) + 2Mg(s) → Si(s) + 2MgCl2(s)

Balancing Reaction (c)

Reaction (c): Na2SiF6(s) + Na(s) → Si(s) + NaF(s) First, let's balance the Si atoms: Na2SiF6(s) + Na(s) → Si(s) + 2NaF(s) (we added 2NaF to balance the amount of Si) Now we need to balance Na atoms: 2Na2SiF6(s) + 4Na(s) → Si(s) + 12NaF(s) (we multiplied each reactant and product by needed coefficients to balance the Na atoms) Finally, let's verify if the F atoms are balanced: 2Na2SiF6(s) + 4Na(s) → Si(s) + 12NaF(s) (Yes, there are 12 F atoms on both sides) So, the balanced equation for reaction (c) is: 2Na2SiF6(s) + 4Na(s) → Si(s) + 12NaF(s)

Key concepts

Chemical Equations

Chemical equations are symbolic representations of chemical reactions, displaying the reactants consumed and the products formed during the reaction. They also convey the conservation of mass through the equal number of atoms of each element on both sides of the equation. A properly written chemical equation will reflect the changes of a chemical process, indicating the states of matter of reactants and products as solid (s), liquid (l), gas (g), or aqueous (aq).

In the given exercise example, silicon production is described through a series of reactions. For instance, the reactions detail transforming silicon dioxide to silicon as well as converting silicon tetrachloride into solid silicon and magnesium chloride. Chemical equations play a critical role in understanding these transformations at a molecular level.

Stoichiometry

Stoichiometry is the quantitative relationship between reactants and products in a chemical reaction. It's based on the principle that matter cannot be created or destroyed in a chemical reaction—only rearranged. This concept forms the basis for calculations involving the mass of reactants and products, using molar masses and coefficients from the balanced chemical equations.

For example, the stoichiometry of the reaction involving silicon dioxide and carbon suggests that one mole of silicon dioxide reacts with one mole of carbon to produce one mole of silicon and one mole of carbon monoxide. Understanding these mole-to-mole ratios is crucial in determining how much reactant is needed, or how much product can be produced, in a given reaction.

Reaction Balancing

Balancing chemical reactions is the act of equalizing the number of each type of atom on both sides of the chemical equation. This ensures the law of conservation of mass is satisfied. When balancing reactions, one typically adjusts the coefficients, which are the numbers placed before the compounds in the equation.

For the given exercise, reactions b and c required balancing. By changing the coefficients, we can ensure that the number of atoms for each element is the same on both sides. This step is mandatory; without a balanced equation, any stoichiometric calculations based on the reaction would be incorrect. Mastering the skill of balancing reactions is essential for any student studying chemistry.