Question

Magnesium ions are remeved in water treatment by the addition of slaked lime, \(\mathrm{Ca}(\mathrm{OH})_{2}\). Write a balanced chemical equation to describe what occurs in this process.

Short answer

The balanced chemical equation for the removal of magnesium ions in water treatment by the addition of slaked lime is: \(Mg^{2+} \text{ (aq)} + Ca(OH)_2\text{ (s)} \rightarrow Mg(OH)_2\text{ (s)} + Ca^{2+}\text{ (aq)} \)

Step-by-step solution

Identify Reactants and Products

The reactants in this process are magnesium ions (Mg²⁺) present in the water and slaked lime (Ca(OH)₂). The reaction between them will form a precipitate of magnesium hydroxide (Mg(OH)₂) and release calcium ions (Ca²⁺) into the water.

Write the Unbalanced Chemical Equation

Now, we can write the unbalanced chemical equation, showing the reactants and products: Mg²⁺ (aq) + Ca(OH)₂ (s) → Mg(OH)₂ (s) + Ca²⁺ (aq)

Balance the Chemical Equation

Next, we need to balance the equation by ensuring the same number of atoms for each element on both sides. The current equation is: Mg²⁺ + Ca(OH)₂ → Mg(OH)₂ + Ca²⁺ Now, let's check the number of atoms for each element: - Mg: 1 on the left side, 1 on the right side - Ca: 1 on the left side, 1 on the right side - O: 2 on the left side, 2 on the right side - H: 2 on the left side, 2 on the right side As we can see, the number of atoms for each element is already balanced on both sides. Therefore, the final balanced chemical equation is: Mg²⁺ (aq) + Ca(OH)₂ (s) → Mg(OH)₂ (s) + Ca²⁺ (aq)

Key concepts

Chemical Reaction

At the heart of chemistry lies the concept of a chemical reaction, which is a process where substances, known as reactants, transform into new substances called products. In a reaction, the bonds between atoms in the reactants break, and new bonds form to create the products. This process involves changes at the molecular level and can result in various observable effects such as energy release, color change, or the formation of solid material in a liquid, known as a precipitate. For students, visualizing these molecular changes can aid in understanding how reactants become products. A key aspect of chemical reactions is the law of conservation of mass, which states that mass is neither created nor destroyed in a chemical reaction. This is why carefully balancing a chemical equation is crucial—it ensures that the number of each type of atom is the same on both the reactant and product sides of the equation.

Understanding the nature of a chemical reaction is essential for grasping other core concepts in chemistry, including stoichiometry, which deals with the quantitative aspects of chemical formulas and reactions, and precipitation reactions, which are fundamental in various fields such as water treatment chemistry.

Precipitation Reaction

A precipitation reaction is a type of chemical reaction in which two soluble reactants combine to form an insoluble product, a precipitate. In the given exercise, the reaction between magnesium ions (Mg²⁺) in the water and slaked lime (Ca(OH)₂) forms magnesium hydroxide (Mg(OH)₂), which precipitates out of the solution. These reactions are not only fascinating from a theoretical standpoint but also have practical applications. In the water treatment process, for example, precipitation reactions facilitate the removal of undesirable ions from water.

• Identification of Reactants: Recognize the starting materials in the reaction.
• Formation of Precipitate: Understand the product(s) that will fall out of the solution as a solid.
• Significance in Applications: Relate the concept to real-world uses such as removing impurities.

Analogies can be drawn between precipitation reactions and real life, such as how certain elements 'get along' much like how certain people's personalities might mesh to form bonds or friendships.

Stoichiometry

Stoichiometry is the section of chemistry that covers the calculation of the quantities of reactants and products in a chemical reaction. It is built on the principle that in a balanced chemical equation, the ratio of the amounts of reactants and products is represented by coefficients, which are the numbers placed before the chemical formulas in the reaction. These coefficients correspond to the number of molecules or moles (a unit of measure in chemistry indicating a specific number of particles) involved in the reaction.

• Study of Quantities: Focus on the proportional relationship between reactants and products in a chemical reaction.
• Understanding Coefficients: Grasp how coefficients indicate the amount of each substance in a reaction.
• Mathematical Calculations: Learn to use stoichiometry to calculate unknown quantities based on the balanced equation.

To truly understand stoichiometry, students must practice balancing equations, which involves ensuring that the number of atoms for each element is equal on both sides of the reaction, as demonstrated in our original exercise. It is akin to a recipe, where each ingredient must be used in a precise ratio to obtain the desired result.

Water Treatment Chemistry

Water treatment chemistry involves a variety of processes designed to make water more acceptable for a specific end use, such as drinking, industrial supply, or river flow maintenance. The treatment process often involves the removal of contaminants or reducing their concentration so that the water becomes fit for use. Chemical reactions, like precipitation reactions, are frequently employed to remove soluble substances by converting them into insoluble forms, which can then be filtered out.

• Removal of Impurities: Understand how different chemical reactions are applied to treat water.
• Formation of Insoluble Compounds: Study how precipitation makes it easier to separate contaminants from water.
• Ensuring Safety: Learn about the methods used to make water safe for consumption and other uses.

An example of water treatment chemistry in action is the use of slaked lime to remove magnesium hardness from water. In this scenario, the addition of slaked lime leads to a precipitation reaction that results in the formation of magnesium hydroxide, a solid that can be filtered from the water, thus making it softer and suitable for usage.