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 \(\mathrm{O}_{2}\) out of carbon dioxide and water. (c) When carbonate salts dissolve in water, they produce basic solutions.

Short answer

a) 2Mg + CO2 -> C + 2MgO b) 6CO2 + 6H2O + solar energy -> C6H12O6 + 6O2 c) CaCO3(s) + H2O(l) -> Ca^2+(aq) + 2 HCO3^-(aq)

Step-by-step solution

a) Burning magnesium metal in a carbon dioxide atmosphere

The given reaction states that magnesium metal (Mg) is burned in carbon dioxide atmosphere (CO2), which results in the reduction of CO2 to carbon (C). Magnesium oxide (MgO) is also produced. To write the balanced equation for this reaction, ensure that the number of atoms of each element (Mg, C, and O) remains the same on both sides of the equation: 2Mg + CO2 -> C + 2MgO Here, 2 Mg atoms, 1 C atom, and 2 O atoms are present on both sides of the equation, which is now balanced.

b) Photosynthesis

In photosynthesis, solar energy is used to produce glucose (C6H12O6) and oxygen (O2) out of carbon dioxide (CO2) and water (H2O). The balanced equation for photosynthesis is: 6CO2 + 6H2O + solar energy -> C6H12O6 + 6O2 This shows that 6 molecules of carbon dioxide and 6 molecules of water are required to produce 1 molecule of glucose and 6 molecules of oxygen. The equation is now balanced, with 6 C atoms, 12 H atoms, and 18 O atoms on both sides.

c) Dissolution of carbonate salts in water

When carbonate salts dissolve in water, they produce basic solutions. For this example, let's consider the dissolution of calcium carbonate (CaCO3) in water (H2O) which produces calcium ions (Ca^2+) and bicarbonate ions (HCO3-) as a result: CaCO3(s) + H2O(l) -> Ca^2+(aq) + 2 HCO3^-(aq) The equation above shows that 1 molecule of calcium carbonate reacts with 1 molecule of water to produce 1 calcium ion and 2 bicarbonate ions. The equation is balanced with 1 Ca atom, 1 C atoms, 3 O atoms, and 3 H atoms on each side of the equation.

Key concepts

Balancing Chemical Equations

Balancing chemical equations is a fundamental skill in chemistry that ensures the law of conservation of mass is observed. This law states that matter cannot be created or destroyed in a chemical reaction; therefore, the number of atoms for each element must remain constant before and after the reaction. Let's revisit the example of burning magnesium in a carbon dioxide atmosphere from the textbook.

The initial equation may appear as: Mg + CO2 -> C + MgO. However, this is not balanced. By inspecting the equation, we see that there are discrepancies in the number of oxygen atoms on each side. To balance it, start by adjusting the coefficients: 2 Mg + CO2 -> C + 2 MgO. This adjustment ensures that we have two magnesium atoms on both sides and the oxygen atoms are also balanced because we have two oxygen atoms from the CO2 and two from the resultant MgO.

Balancing equations requires practice and often involves a trial and error approach to find the right coefficients. A tip for students: always balance the elements that appear in the least number of compounds first, and save hydrogen and oxygen for last since they are often found in multiple compounds.

Photosynthesis Reaction

The photosynthesis reaction is a process by which plants, algae, and some bacteria convert light energy into chemical energy stored in glucose, a sugar. The overall balanced equation represents a complex series of steps involving the transformation of sunlight, carbon dioxide, and water into glucose and oxygen. The balanced chemical equation is a simplified representation of this miraculous natural process: 6CO2 + 6H2O + solar energy -> C6H12O6 + 6O2.

This equation encapsulates the importance of photosynthesis in sustaining life on Earth, as it is the foundation for the food web. The equation shows that six molecules of carbon dioxide and six molecules of water, using energy from sunlight, produce one molecule of glucose and six molecules of oxygen. For students learning this concept, it's crucial to understand that the solar energy is not a 'reactant' in the traditional sense, but rather an energy source that drives the reaction. Moreover, photosynthesis is an endothermic reaction, meaning it absorbs energy, which is a significant concept in understanding energy flow in chemical processes.

Carbonate Dissolution

Carbonate dissolution involves the breakdown of carbonate minerals, such as calcium carbonate (CaCO3), when they interact with water. This chemical process is relevant not just in chemistry, but also in geological and environmental sciences. For instance, the dissolution of carbonate rocks like limestone is fundamental to the formation of karst landscapes and is also a crucial part of the carbon cycle.

When calcium carbonate dissolves in water, as shown in the textbook example, the balanced reaction is: CaCO3(s) + H2O(l) -> Ca^2+(aq) + 2 HCO3^-(aq). This shows that the solid calcium carbonate interacts with liquid water to form aqueous calcium ions and bicarbonate ions. Notably, this process is influenced by the acidity or basicity of the solution; in pure water, a small amount of carbonate will dissolve, forming a basic solution due to the production of bicarbonate ions which are alkaline.

For students, it is key to understand that 'aq' denotes the state of being aqueous or dissolved in water, and 's' denotes solid. Recognizing the states of reactants and products is crucial in predicting the outcomes of a reaction, as well as understanding the behavior of compounds in different environments.