Question

Complete and balance each of the following skeletal equations: (a) \(\mathrm{H}_{2} \mathrm{~S}(\mathrm{aq})+\mathrm{O}_{2}(\mathrm{~g}) \rightarrow\) (b) \(\mathrm{CaO}\) (s) \(+\mathrm{H}_{2} \mathrm{O}\) (l) \(\rightarrow\) (c) \(\mathrm{H}_{2} \mathrm{~S}(\mathrm{~g})+\mathrm{SO}_{2}(\mathrm{~g}) \rightarrow\)

Short answer

\( 2\mathrm{H}_{2}\mathrm{S}(\mathrm{aq}) + 3\mathrm{O}_{2}(\mathrm{g}) \rightarrow 2\mathrm{SO}_{2}(\mathrm{g}) + 2\mathrm{H}_{2}\mathrm{O}(\mathrm{l}) \); \( \mathrm{CaO}(\mathrm{s}) + \mathrm{H}_{2}\mathrm{O}(\mathrm{l}) \rightarrow \mathrm{Ca}(\mathrm{OH})_{2}(\mathrm{s}) \); \( 2\mathrm{H}_{2}\mathrm{S}(\mathrm{g}) + 1\mathrm{SO}_{2}(\mathrm{g}) \rightarrow 2\mathrm{H}_{2}\mathrm{O}(\mathrm{l}) + 3\mathrm{S}(\mathrm{s}) \).

Step-by-step solution

Balancing the Hydrogen Sulfide and Oxygen Reaction

Start by writing down the reactants and products. Hydrogen sulfide reacts with oxygen to form sulfur dioxide and water. The unbalanced equation is: \( \mathrm{H}_{2}\mathrm{S}(\mathrm{aq}) + \mathrm{O}_{2}(\mathrm{g}) \rightarrow \mathrm{SO}_{2}(\mathrm{g}) + \mathrm{H}_{2}\mathrm{O}(\mathrm{l}) \). Now balance the atoms in the equation. There are 2 hydrogens and 2 oxygens on the left side and 2 hydrogens and 3 oxygens on the right. By adding coefficients to balance atoms, we get: \( 2\mathrm{H}_{2}\mathrm{S}(\mathrm{aq}) + 3\mathrm{O}_{2}(\mathrm{g}) \rightarrow 2\mathrm{SO}_{2}(\mathrm{g}) + 2\mathrm{H}_{2}\mathrm{O}(\mathrm{l}) \).

Balancing the Calcium Oxide and Water Reaction

Write down the reactants and expected product for the reaction. Calcium oxide reacts with water to form calcium hydroxide. The initial unbalanced equation is: \( \mathrm{CaO}(\mathrm{s}) + \mathrm{H}_{2}\mathrm{O}(\mathrm{l}) \rightarrow \mathrm{Ca}(\mathrm{OH})_{2}(\mathrm{s}) \). Balancing this reaction is straightforward as it requires placing a coefficient of 1 in front of each formula: \( 1\mathrm{CaO}(\mathrm{s}) + 1\mathrm{H}_{2}\mathrm{O}(\mathrm{l}) \rightarrow 1\mathrm{Ca}(\mathrm{OH})_{2}(\mathrm{s}) \). Everything is already balanced, so this is the final balanced equation.

Balancing the Reaction of Hydrogen Sulfide and Sulfur Dioxide

List the reactants and expected products. When hydrogen sulfide reacts with sulfur dioxide, an expected product is water and sulfur. The initial unbalanced equation is: \( \mathrm{H}_{2}\mathrm{S}(\mathrm{g}) + \mathrm{SO}_{2}(\mathrm{g}) \rightarrow \mathrm{H}_{2}\mathrm{O}(\mathrm{l}) + \mathrm{S}(\mathrm{s}) \). To balance this, we notice that there is an odd number of oxygen atoms on the reactant side and even on the product side. If we put a coefficient 2 in front of \( \mathrm{H}_{2}\mathrm{O} \) to have an even number of oxygen atoms on both sides, the equation becomes: \( 2\mathrm{H}_{2}\mathrm{S}(\mathrm{g}) + 1\mathrm{SO}_{2}(\mathrm{g}) \rightarrow 2\mathrm{H}_{2}\mathrm{O}(\mathrm{l}) + 3\mathrm{S}(\mathrm{s}) \). This balances hydrogen, sulfur, and oxygen atoms on both sides of the equation.

Key concepts

Stoichiometry

Stoichiometry is the branch of chemistry that deals with the quantitative relationships between reactants and products in a chemical reaction. Students often describe it as the recipe for chemistry because it tells you how much of each reactant you need to create a certain amount of product, much like how a cooking recipe tells you how much of each ingredient you need.

Consider the analogy of baking a cake, where the recipe requires specific ratios of flour, eggs, and sugar. In stoichiometry, instead of cake ingredients, we deal with chemical substances. If your recipe (chemical equation) is 'balanced', you will have the exact amount of cake (product) you intended to make without any leftover ingredients (reactants).

Chemical Reactions

Chemical reactions are processes where substances, known as reactants, transform into new substances, called products. This transformation involves the breaking and forming of chemical bonds, which requires the input or release of energy. There are different types of reactions such as synthesis, decomposition, single replacement, double replacement, and combustion.

Example of a Chemical Reaction:

When vinegar (acetic acid) reacts with baking soda (sodium bicarbonate), the chemical reaction produces carbon dioxide gas, water, and sodium acetate. This is an example of a double replacement reaction combined with decomposition.

Reaction Stoichiometry

Reaction stoichiometry specifically refers to the calculations involved in finding the amounts of reactants and products in a chemical reaction using the balanced chemical equation. It involves using the mole concept, as moles provide a consistent method to convert between atoms, molecules, grams, and liters for gases at standard temperature and pressure (STP).

When solving stoichiometric problems, it's important to:

• Write a balanced chemical equation.
• Use the mole ratio from the balanced equation to calculate the moles of the desired substance.
• Convert moles to grams, particles, or volume as needed.

Balancing Equations

Balancing equations is fundamental to the study of chemistry because it ensures that the law of conservation of mass is obeyed in a chemical reaction. This scientific law states that mass can neither be created nor destroyed. Therefore, the mass of the reactants must equal the mass of the products.

Steps to balance a chemical equation:

• Write down the unbalanced equation.
• List the number of each type of atom present on both sides of the equation.
• Add coefficients in front of the chemical formulas to balance the number of atoms. Remember, coefficients apply to the entire molecule.
• Repeat the process until all atoms are balanced on both sides of the equation.
• Finally, check to ensure that you have the simplest whole-number ratio.

Don't change the subscripts in the chemical formulas; this would change the substances involved in the reaction. Balancing equations often requires practice to develop intuition and efficiency.