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

Balancing chemical equations is a foundational skill in chemistry that ensures the law of conservation of mass is respected. It involves adjusting the coefficients of the reactants and products to ensure that the number of atoms for each element is the same on both sides of the reaction.

For example, looking at the reaction where silicon tetrachloride reacts with magnesium, we initially write the unbalanced equation as \[\mathrm{SiCl}_4 + \mathrm{Mg} \longrightarrow \mathrm{Si} + \mathrm{MgCl}_2\]. To balance it, we see that there are four chlorine atoms in silicon tetrachloride, so we need two magnesium chloride molecules to balance it out, resulting in the balanced equation \[\mathrm{SiCl}_4 + 2\mathrm{Mg} \longrightarrow \mathrm{Si} + 2\mathrm{MgCl}_2\]. Each side of the equation now has one silicon atom, four chlorine atoms, and two magnesium atoms, thus maintaining the same amount of each atom in both reactants and products.

When balancing equations, remember to:

• Count the number of atoms of each element on both sides of the equation.
• Use coefficients to balance the elements one at a time.
• Double-check your work to make sure you haven't changed the original compounds or created an impossible reaction.

Stoichiometry is the quantitative relationship between reactants and products in a chemical reaction. It's based on the balanced chemical equation and provides insights into the amount of substances consumed and produced.

Consider the second example from our text where we balanced the silicon tetrachloride and magnesium reaction. Stoichiometry enables us to predict how much magnesium is needed to fully react with a given amount of silicon tetrachloride, or vice-versa. In the balanced equation \[\mathrm{SiCl}_4 + 2\mathrm{Mg} \longrightarrow \mathrm{Si} + 2\mathrm{MgCl}_2\], the stoichiometric coefficients tell us that each mole of silicon tetrachloride reacts with two moles of magnesium to produce one mole of silicon and two moles of magnesium chloride.

These coefficients are the key to calculations such as determining the mass of reactants needed or the yield of products that can be expected from a given mass of reactants—essential for processes ranging from small-scale lab experiments to large-scale industrial productions.

Chemical reactions can be classified into different types based on the changes that occur at the molecular level. Common types include synthesis, decomposition, single replacement, and double replacement reactions.

For instance, the reaction \[\mathrm{Na}_2\mathrm{SiF}_6(s) + 6\mathrm{Na}(s) \longrightarrow \mathrm{Si}(s) + 12\mathrm{NaF}(s)\] where sodium reacts with sodium hexafluorosilicate is a form of single replacement reaction. In it, sodium atoms replace other elements in a compound, leading to a new arrangement of atoms and the formation of new substances. Understanding the type of reaction not only aids in predicting the products but also provides guidance on how to approach the balancing of the chemical equation.

Moreover, recognizing reaction types is useful in predicting reaction behavior, such as energy release or absorption, and in identifying what kind of catalyst or conditions may be necessary for a reaction to occur.