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.

Short answer

For the given reactions, the balanced chemical equations are as follows: (a) Burning magnesium in carbon dioxide: \(2Mg + CO_2 \rightarrow 2MgO + C\) (b) Photosynthesis: \(6CO_2 + 6H_2O \rightarrow C_6H_{12}O_6 + 6O_2\) (c) Dissolving carbonate salts in water: \(M_2CO_3 + 2H_2O \rightarrow 2M(OH)_2 + H_2CO_3\)

Step-by-step solution

Reaction (a): Burning magnesium in carbon dioxide

Magnesium metal (Mg) reacts with carbon dioxide (CO2) after burning, leading to the formation of magnesium oxide (MgO) and elemental carbon (C). Write the unbalanced equation: Mg + CO2 -> MgO + C Now, balance the equation by adjusting the coefficients: 2Mg + CO2 -> 2MgO + C

Reaction (b): Photosynthesis

In the photosynthesis process, carbon dioxide (CO2) and water (H2O) are used to produce glucose (C6H12O6) and oxygen gas (O2) with the help of solar energy. Write the unbalanced equation: CO2 + H2O -> C6H12O6 + O2 Now, balance the equation by adjusting the coefficients: 6CO2 + 6H2O -> C6H12O6 + 6O2

Reaction (c): Dissolving carbonate salts in water

When carbonate salts (M2CO3, where M represents a metal) dissolve in water (H2O), they produce basic solutions with the formation of metal hydroxide (M(OH)2) and carbonic acid (H2CO3). Note that carbonic acid further decomposes into CO2 and H2O. Write the unbalanced equation: M2CO3 + H2O -> M(OH)2 + H2CO3 Then, to keep it balanced, adjust the coefficients: M2CO3 + 2H2O -> 2M(OH)2 + H2CO3

Key concepts

Chemical Equation Balancing

Chemical reactions are represented by chemical equations, where the reactants are shown on the left and the products on the right. The principle of the conservation of mass dictates that the number of atoms of each element should be equal on both sides of the equation. Balancing chemical equations involves adding coefficients, the numbers in front of the chemical formulas, to ensure this equality.

For example, in the combustion of magnesium in a carbon dioxide atmosphere, the unbalanced equation is:
Mg + CO2 -> MgO + C.
Upon balancing, we ensure that the amount of each atom is the same on both sides, resulting in:
2Mg + CO2 -> 2MgO + C.
This equation now adheres to the conservation of mass and correctly represents the reaction.

Photosynthesis Reaction

Photosynthesis is a fundamental biological process in which plants, using the energy from sunlight, convert carbon dioxide (CO2) and water (H2O) into glucose (C6H12O6) and oxygen (O2). This reaction is crucial for life on Earth as it is the basis for the majority of the planet's food chains and also plays a vital role in the regulation of atmospheric CO2 levels.

The general balanced equation for photosynthesis is:
6CO2 + 6H2O + light energy -> C6H12O6 + 6O2.
It's important for students to understand that balancing this equation requires careful attention to the stoichiometry—the quantitative relationships between reactants and products in a chemical reaction. The presence of light energy in the equation emphasizes that this is not a spontaneous reaction but one that requires an energy input to proceed.

Dissolving Carbonate Salts

Carbonate salts are ionic compounds that can dissolve in water to produce basic solutions. Basic, or alkaline, solutions result when the hydroxide ion (OH-) concentration is greater than the hydrogen ion (H+) concentration. When carbonate salts (M2CO3) dissolve in water, a metal hydroxide (M(OH)2) is formed, along with carbonic acid (H2CO3), which in itself is unstable and decomposes into CO2 and H2O.

A balanced equation representing this process might look like this:
M2CO3 + 2H2O -> 2M(OH)2 + H2CO3.
This reaction demonstrates the tendency of carbonate salts to increase the pH of a solution, thus making it more basic. The balancing of this equation takes into account that two water molecules are needed to form two hydroxide groups for each dissolved carbonate salt molecule.