Question

Complete and balance the following equations: (a) \(\mathrm{Mg}(\mathrm{s})+\mathrm{H}_{2} \mathrm{O}(l) \longrightarrow\) (b) \(\mathrm{SrO}(\mathrm{s})+\mathrm{H}_{2} \mathrm{O}(l) \longrightarrow\) (c) \(\mathrm{N}_{2} \mathrm{O}_{5}(g)+\mathrm{H}_{2} \mathrm{O}(l) \longrightarrow\)

Short answer

(a) Mg(s) + 2 H₂O(l) → Mg(OH)₂(aq) + H₂(g), (b) SrO(s) + H₂O(l) → Sr(OH)₂(aq), (c) N₂O₅(g) + H₂O(l) → 2 HNO₃(aq).

Step-by-step solution

Identify the Type of Reaction

The first step is to recognize the type of chemical reaction presented in each equation. Generally, we observe if the reaction may be a synthesis, decomposition, single replacement, or double replacement based on the reactants.

Predict Products

For each reaction, predict the chemical products that will be formed: (a) For magnesium and water, magnesium hydroxide (Mg(OH)₂) will be formed, with hydrogen gas (H₂) released. (b) Strontium oxide with water forms strontium hydroxide (Sr(OH)₂). (c) Dinitrogen pentoxide reacts with water to form nitric acid (HNO₃).

Write the Unbalanced Equations

Write the unbalanced form of each equation including the predicted products: (a) Mg(s) + H₂O(l) → Mg(OH)₂(aq) + H₂(g) (b) SrO(s) + H₂O(l) → Sr(OH)₂(aq) (c) N₂O₅(g) + H₂O(l) → HNO₃(aq)

Balance Equation (a)

To balance the reaction of magnesium with water, ensure the number of atoms of each element is the same on both sides: For equation (a): - Mg(s) + 2 H₂O(l) → Mg(OH)₂(aq) + H₂(g). This gives us 1 magnesium, 4 hydrogen, and 2 oxygen atoms on both sides.

Balance Equation (b)

To balance the reaction of strontium oxide with water, make sure each type of atom on both sides is equal: For equation (b): - SrO(s) + H₂O(l) → Sr(OH)₂(aq). This equation is already balanced with 1 strontium, 2 oxygen, and 2 hydrogen atoms on both sides.

Balance Equation (c)

For the reaction of dinitrogen pentoxide with water, balance all elements: For equation (c): - N₂O₅(g) + H₂O(l) → 2 HNO₃(aq). This results in 2 nitrogen, 6 oxygen, and 2 hydrogen atoms on each side, completing the balance.

Key concepts

Chemical Reactions

Chemical reactions are fundamental processes that occur when substances, known as reactants, transform into different substances called products. These transformations involve changes in the arrangement of atoms and the breaking and forming of bonds.
Chemical reactions can be observed through a variety of signs, such as color changes, gas production, the formation of a precipitate, or energy changes like heat or light emission. These indicators provide evidence that a chemical change has taken place.
In the context of the exercise given, we deal with reactions where magnesium, strontium oxide, and dinitrogen pentoxide react with water. These reactions are typical of synthesis reactions where new compounds are formed from simpler substances.

Predicting Products

The art of predicting products in a chemical reaction stems from understanding the reactants' nature and the reaction conditions. Based on the reactants present, one can often deduce what type of reaction might occur and what products are likely to form.
For instance, when magnesium reacts with water, magnesium hydroxide is formed, and hydrogen gas is released. This prediction stems from the typical behavior of metals like magnesium in water, which often yields a hydroxide and hydrogen gas.
In another example, where strontium oxide reacts with water, strontium hydroxide is formed. Water aids in breaking down the reactant, producing a base here. Similarly, with dinitrogen pentoxide and water, the expected product is nitric acid, resulting from the dissolution of the oxide in water.
Understanding these transformations can greatly simplify balancing chemical equations and predicting the reaction outcomes.

Types of Reactions

Chemical reactions can be classified into several categories, making it easier to predict the outcomes and understand the processes involved.

• Synthesis Reactions: Involved in building complex products from simple reactants. For instance, the formation of magnesium hydroxide from magnesium and water is a synthesis reaction.
• Decomposition Reactions: Broken down complex substances into simpler ones is their hallmark.
• Single Replacement Reactions: Where one element replaces another in a compound, typically usually metals or halogens.
• Double Replacement Reactions: Occur when elements in different compounds exchange places to form two new compounds.

Recognizing the type of reaction can be crucial when predicting reaction products. In this exercise, all reactions involve synthesis. By identifying the reaction types, students can apply similar logic to solve different chemical equations effectively.