Balance the following chemical equations. (a) \(\mathrm{HNO}_{3}+\mathrm{Ca}(\mathrm{OH})_{2} \rightarrow \mathrm{Ca}\left(\mathrm{NO}_{3}\right)_{2}+\mathrm{H}_{2} \mathrm{O}\) (b) \(\mathrm{NaOH}+\mathrm{H}_{2} \mathrm{SO}_{4} \rightarrow \mathrm{Na}_{2} \mathrm{SO}_{4}+\mathrm{H}_{2} \mathrm{O}\) (c) \(\mathrm{NaCl}+\mathrm{AgNO}_{3} \rightarrow \mathrm{AgCl}+\mathrm{NaNO}_{3}\) (d) \(\mathrm{BaCl}_{2}+\mathrm{H}_{2} \mathrm{SO}_{4} \rightarrow \mathrm{BaSO}_{4}+\mathrm{HCl}\)

A chemical reaction involves the transformation of one or more substances into different substances. This process involves the breaking of bonds in reactants and the formation of new bonds in products. In a chemical reaction, the substances that start the reaction are called reactants, and the substances that result from the reaction are called products. For example, in the balanced equation:
\[ 2HNO_3 + Ca(OH)_2 \rightarrow Ca(NO_3)_2 + 2H_2O \]
Here, \( HNO_3 \) and \( Ca(OH)_2 \) are reactants, while \( Ca(NO_3)_2 \) and \( H_2O \) are products.
By understanding the nature of reactants and products, you can better predict the outcomes of various chemical reactions. Do you know that chemical reactions have different types like synthesis, decomposition, single displacement, and double displacement? Each type has its unique pattern and characteristics.

Stoichiometry is the part of chemistry that deals with the quantitative relationships between reactants and products in a chemical reaction. It's like the recipe of a reaction, specifying how much of each component is involved.
Take the balanced chemical equation: \[ 2NaOH + H_2SO_4 \rightarrow Na_2SO_4 + 2H_2O \]
This equation tells us that 2 moles of \( NaOH \) react with 1 mole of \( H_2SO_4 \) to produce 1 mole of \( Na_2SO_4 \) and 2 moles of \( H_2O \). The coefficients (numbers in front of the formulas) provide the mole ratio of reactants and products.
Mastering stoichiometry allows you to predict the amounts of substances consumed and produced in a reaction, which is crucial for laboratory work and industrial applications. It's like knowing the exact quantity of ingredients needed to bake a cake.

Molecular equations show the complete chemical formulas of reactants and products. They provide a clear picture of the substances involved in a chemical reaction. For instance, the equation:
\[ NaCl + AgNO_3 \rightarrow AgCl + NaNO_3 \]
shows sodium chloride \( NaCl \) reacting with silver nitrate \( AgNO_3 \) to produce silver chloride \( AgCl \) and sodium nitrate \( NaNO_3 \).
Molecular equations are helpful because they give you a straightforward view of the reaction process, including the compounds that change and the new compounds formed. It's like a summary of the whole chemical process in one line. Additionally, molecular equations underline the importance of understanding chemical formulas, as each represents a molecule's actual composition.

The law of conservation of mass states that mass is neither created nor destroyed in a chemical reaction. This principle ensures that the total mass of the reactants equals the total mass of the products. For example, in the balanced reaction:
\[ BaCl_2 + H_2SO_4 \rightarrow BaSO_4 + 2HCl \]
if you start with a specific mass of \( BaCl_2 \) and \( H_2SO_4 \), the total mass of \( BaSO_4 \) and \( HCl \) produced will be the same.
This law helps with balancing chemical equations, as it requires that the number of each type of atom on the reactants' side must equal the number on the products' side. This concept ensures that calculations in chemistry adhere to real-world observations, maintaining the consistency and predictability of chemical reactions.