Problem 68 - Chemistry The Central Science In Si Units

Question

Write a balanced equation for each of the following reactions: (a) Burning magnesium metal in a carbon dioxide atmosphere reduces the \(\mathrm{CO}_{2}\) to carbon. (b) In photosynthesis, solar energy is used to produce glucose \(\left(\mathrm{C}_{6} \mathrm{H}_{12} \mathrm{O}_{6}\right)\) and \(\mathrm{O}_{2}\) from carbon dioxide and water. (c) When carbonate salts dissolve in water, they produce basic solutions.

Step-by-Step Solution

Answer

(a) \(2\text{Mg} + \text{CO}_2 \rightarrow 2\text{MgO} + \text{C}\); (b) \(6\text{CO}_2 + 6\text{H}_2\text{O} \rightarrow \text{C}_6\text{H}_{12}\text{O}_6 + 6\text{O}_2\); (c) Carbonate ions \(\text{CO}_3^{2-}\) when dissolved, lead to basic solutions by forming \(\text{OH}^-\).

Step 1: Identify the reactants and products (a)

For (a), magnesium (Mg) reacts with carbon dioxide (CO2) to produce magnesium oxide (MgO) and carbon (C). This reaction involves the combustion of magnesium in carbon dioxide, resulting in the reduction of CO2.

Step 2: Write the unbalanced equation (a)

The unbalanced chemical equation is:\[ \text{Mg} + \text{CO}_2 \rightarrow \text{MgO} + \text{C} \]

Step 3: Balance the equation (a)

Ensure the same number of each type of atom on both sides of the equation. Balance the magnesium and carbon atoms first:\[ 2\text{Mg} + \text{CO}_2 \rightarrow 2\text{MgO} + \text{C} \]

Step 4: Identify the reactants and products (b)

In photosynthesis (b), carbon dioxide (CO2) and water (H2O) react to form glucose (C6H12O6) and oxygen (O2). Solar energy is the driving force of this reaction but is not included in the chemical equation.

Step 5: Write the unbalanced equation (b)

The unbalanced chemical equation for photosynthesis is:\[ \text{CO}_2 + \text{H}_2\text{O} \rightarrow \text{C}_6\text{H}_{12}\text{O}_6 + \text{O}_2 \]

Step 6: Balance the equation (b)

Balance the equation by adjusting the coefficients to ensure the same number of each type of atom on both sides:\[ 6\text{CO}_2 + 6\text{H}_2\text{O} \rightarrow \text{C}_6\text{H}_{12}\text{O}_6 + 6\text{O}_2 \]

Step 7: Explain carbonate salts dissolving (c)

When carbonate salts dissolve in water, they generally dissociate into ions, leading to a basic solution because the carbonate ion (CO3^2-) reacts with water to form bicarbonate (HCO3^-) and hydroxide ions (OH^-), resulting in increased OH^-.

Step 8: Write the general reaction equation (c)

The reaction for a carbonate salt dissolving in water is typically written as:\[ \text{CO}_3^{2-} + \text{H}_2\text{O} \rightarrow \text{HCO}_3^- + \text{OH}^- \]

Key Concepts

Chemical Reactions

Chemical reactions involve the transformation of substances through the breaking and forming of chemical bonds. In these processes, the original substances, called reactants, interact to form different substances, known as products.
One thing to always keep in mind is the principle of conservation of mass, which states that mass is neither created nor destroyed in a chemical reaction. This principle means that the number of atoms for each element must be the same before and after the reaction, leading to the balancing of chemical equations.

To balance a chemical equation, adjust the coefficients of the reactants and products until the number of atoms for each element is equal on both sides of the equation. This systematic approach ensures you reflect the conservation of mass accurately. Remember to write the reactants on the left side of the equation and the products on the right, using an arrow ( rrow) to indicate the direction of the reaction.

Let's explore how this concept is applied in different scenarios such as burning magnesium in carbon dioxide or the process of photosynthesis.

Photosynthesis Equation

Photosynthesis is a fundamental chemical reaction that occurs in plants, algae, and some bacteria. In this process, these organisms convert light energy, usually from the sun, into chemical energy stored in glucose molecules. This reaction is essential for life on Earth because it is the primary source of organic matter for nearly all organisms.
During photosynthesis, carbon dioxide (O_2) and water (H_2O) act as the reactants. With the help of sunlight absorbed by chlorophyll in plant cells, these reactants are transformed into glucose (_6H_{12}O_6) and oxygen gas (O_2) as the products. The balanced photosynthesis equation is:

• 6CO_2 + 6H_2O rrow C_6H_{12}O_6 + 6O_2

The equation reflects the conservation of mass by showing that the number of each type of atom is the same on both sides. Plus, it demonstrates how plants not only produce food for themselves but also release oxygen, which is critical for animal respiration.
In summary, photosynthesis is not just another chemical equation; it is a remarkable process that transforms carbon dioxide and water into life-sustaining glucose and oxygen using the power of sunlight.

Basic Solutions Chemistry

In chemistry, solutions can be classified based on their pH levels as acidic, neutral, or basic. Basic solutions, also called alkaline solutions, are characterized by a pH greater than 7. This high pH results from a greater concentration of hydroxide ions (OH\(^-\)) than hydrogen ions (H\( ^+\)).
One common way to create a basic solution is through the dissolution of carbonate salts in water. When carbonate ions (O_3^{2-}) dissolve in water, they undergo a reaction with water to form bicarbonate ions (HCO_3^-), and hydroxide ions:

• O_3^{2-} + H_2O rrow HCO_3^- + OH^-

This reaction shows how the presence of carbonate ions can increase the concentration of hydroxide ions, resulting in a basic solution. Basic solutions are important in various chemical processes and industrial applications, including cleaning agents and agriculture.
Understanding the behavior of carbonate salts in water can provide insights into water chemistry, environmental science, and industrial processes. By grasping these fundamental concepts, you'll develop a versatile knowledge base in chemistry, aiding both academic pursuits and practical applications.