Problem 129 - General Chemistry: Principles and Modern Applications

Question

Complete and balance equations for these reactions. (a) \(\operatorname{LiH}(s)+H_{2} O(1) \longrightarrow\) (b) \(\mathrm{C}(\mathrm{s})+\mathrm{H}_{2} \mathrm{O}(\mathrm{g}) \stackrel{\Delta}{\longrightarrow}\) (c) \(\mathrm{NO}_{2}(\mathrm{g})+\mathrm{H}_{2} \mathrm{O}(1) \longrightarrow\)

Step-by-Step Solution

Answer

The three balanced equations are: (a) \(\operatorname{LiH}(s)+H_{2} O(l) \longrightarrow LiOH(aq) + H_{2}(g)\), (b) \(\mathrm{C}(s) + H_{2} O(g) \stackrel{\Delta}{\longrightarrow} CO(g) + H_{2}(g)\), (c) \(\mathrm{NO}_{2}(g) + H_{2} O(l) \longrightarrow HNO_{3}(aq) + NO(g)\)

Step 1: Balancing Equation (a)

Equation (a) is as follows \(\operatorname{LiH}(s)+H_{2} O(l) \longrightarrow\). You need to make sure the number and type of atoms on both sides of the equation are equal. The balanced equation is \(\operatorname{LiH}(s)+H_{2} O(l) \longrightarrow LiOH(aq) + H_{2}(g)\)

Step 2: Balancing Equation (b)

Equation (b) is \( \mathrm{C}(s) + H_{2} O(g) \stackrel{\Delta}{\longrightarrow}\). Again, you need to balance the elements on both sides of the equation. The balanced equation would be \(\mathrm{C}(s) + H_{2} O(g) \stackrel{\Delta}{\longrightarrow} CO(g) + H_{2}(g)\)

Step 3: Balancing Equation (c)

Equation (c) is \(\mathrm{NO}_{2}(g) + H_{2} O(l) \longrightarrow\). Balancing the equation would give: \(\mathrm{NO}_{2}(g) + H_{2} O(l) \longrightarrow HNO_{3}(aq) + NO(g)\)

Key Concepts

Stoichiometry

Stoichiometry is a vital concept in chemistry that deals with the quantitative relationships between reactants and products in a chemical reaction. By understanding stoichiometry, you can predict how much of each reactant is needed and what amount of products can be formed. This is crucial when balancing chemical equations, as seen in the given exercise.

When balancing a chemical equation, stoichiometry ensures that the law of conservation of mass is met. This law states that matter is neither created nor destroyed in a chemical reaction. Hence, the same number of each type of atom must appear on both sides of the equation. For example, in equation (a), \[ \text{LiH}(s) + \text{H}_2\text{O}(l) \longrightarrow \text{LiOH}(aq) + \text{H}_2(g) \] each atom of lithium, hydrogen, and oxygen is accounted for on both sides.

Stoichiometric calculations can also help in determining molar ratios. Every balanced chemical equation has coefficients that indicate the proportion of moles of each substance involved. By understanding and applying these ratios, you can calculate various parameters, such as the amounts of gases produced or consumed in a reaction.

Chemical Reactions

Chemical reactions involve the transformation of substances through breaking and forming of bonds, resulting in products that have different properties and compositions than the reactants. This transformation is shown in the form of a chemical equation.

In a chemical reaction, multiple types of reactions can occur, including synthesis, decomposition, single exchange, and double exchange. For instance, equation (b) \[ \text{C}(s) + \text{H}_2\text{O}(g) \stackrel{\Delta}{\longrightarrow} \text{CO}(g) + \text{H}_2(g) \] is a type of redox or reduction-oxidation reaction where carbon is oxidized and water is reduced to produce carbon monoxide and hydrogen gas.

The notation used in chemical reactions includes states of matter:

• (s) for solids
• (l) for liquids
• (g) for gases
• (aq) for aqueous solutions

These notations help in understanding the conditions under which the reaction takes place. In the exercise provided, knowing the state of each substance is crucial for accurate representation and understanding of the reaction.

Aqueous Solutions

An aqueous solution is a solution in which the solvent is water. Aqueous solutions are pivotal in many chemical reactions as water is a common medium where reactions take place. In the context of the exercise, aqueous solutions are referenced in some balanced equations.

For example, in equation (a), \[ \text{LiH}(s) + \text{H}_2\text{O}(l) \longrightarrow \text{LiOH}(aq) + \text{H}_2(g) \] when lithium hydroxide (\( \text{LiOH} \)) is formed, it is an aqueous solution, indicating that the lithium hydroxide has dissolved in water.

Aqueous solutions have unique properties:

• They facilitate the movement of ions, which is essential in reaction kinetics.
• They can change pH, affecting the course and yield of reactions.
• Different solubility levels of compounds in water influence reaction rates and product formations.

The understanding of aqueous solutions helps in predicting the solubility and behavior of substances involved in chemical reactions, optimizing conditions for desired outcomes.