Question

Complete and balance the following equations: (a) \(\mathrm{Mg}_{3} \mathrm{~N}_{2}(s)+\mathrm{H}_{2} \mathrm{O}(l) \longrightarrow\) (b) \(\mathrm{NO}(g)+\mathrm{O}_{2}(g) \longrightarrow\) (c) \(\mathrm{N}_{2} \mathrm{O}_{5}(g)+\mathrm{H}_{2} \mathrm{O}(l) \longrightarrow\) (d) \(\mathrm{NH}_{3}(a q)+\mathrm{H}^{+}(a q) \longrightarrow\) (e) \(\mathrm{N}_{2} \mathrm{H}_{4}(l)+\mathrm{O}_{2}(g) \longrightarrow\)

Short answer

(a) \(1 \times Mg_3N_2(s) + 6 \times H_2O(l) \rightarrow 3 \times Mg(OH)_2(s) + 6 \times NH_3(g)\) (b) \(2 \times NO(g) + 1 \times O_2(g) \rightarrow 2 \times NO_2(g)\) (c) \(1 \times N_2O_5(g) + 2 \times H_2O(l) \rightarrow 2 \times HNO_3(aq)\) (d) \(1 \times NH_3(aq) + 1 \times H^+(aq) \rightarrow 1 \times NH_4^+(aq)\) (e) \(1 \times N_2H_4(l) + 2 \times O_2(g) \rightarrow 1 \times N_2(g) + 4 \times H_2O(l)\)

Step-by-step solution

Analyze initial equation

Mg₃N₂(s) + H₂O(l) → [unknown products]

Determine products

Since Mg₃N₂ reacts with water, the reaction will produce magnesium hydroxide (Mg(OH)₂) and ammonia (NH₃). Mg₃N₂(s) + H₂O(l) → Mg(OH)₂(s) + NH₃(g)

Balance the equation

Balancing the atoms: \( 3 \times\) Mg(OH)₂(s) + \(6 \times\) NH₃(g) ← \(1 \times\) Mg₃N₂(s) + \(6 \times\) H₂O(l) (b) Balancing NO(g) + O₂(g) →

Determine products

NO(g) reacts with O₂(g) to produce nitrogen dioxide (NO₂). NO(g) + O₂(g) → NO₂(g)

Balance the equation

Balancing the atoms: \(2 \times\) NO(g) + \(1 \times\) O₂(g) → \(2 \times\) NO₂(g) (c) Balancing N₂O₅(g) + H₂O(l) →

Determine products

N₂O₅(g) reacts with H₂O(l) to produce nitric acid (HNO₃). N₂O₅(g) + H₂O(l) → HNO₃(aq)

Balance the equation

Balancing the atoms: \( 1 \times \) N₂O₅(g) + \( 2 \times \) H₂O(l) → \( 2 \times \) HNO₃(aq) (d) Balancing NH₃(aq) + H⁺(aq) →

Determine products

NH₃(aq) reacts with H⁺(aq) to produce ammonium ion (NH₄⁺). NH₃(aq) + H⁺(aq) → NH₄⁺(aq)

Balance the equation

In this case, the equation is already balanced: \(1 \times \) NH₃(aq) + \( 1 \times \) H⁺(aq) → \( 1 \times \) NH₄⁺(aq) (e) Balancing N₂H₄(l) + O₂(g) →

Determine products

N₂H₄(l) reacts with O₂(g) to produce nitrogen gas (N₂) and water (H₂O). N₂H₄(l) + O₂(g) → N₂(g) + H₂O(l)

Balance the equation

Balancing the atoms: \( 1 \times \) N₂H₄(l) + \( 2 \times \) O₂(g) → \( 1 \times \) N₂(g) + \( 4 \times \) H₂O(l)

Key concepts

Stoichiometry

Stoichiometry is a fundamental concept in chemistry that involves the calculation of the quantities of reactants and products in chemical reactions. It is based on the conservation of mass and the principle that atoms are neither created nor destroyed in chemical reactions.

When balancing chemical equations, such as the provided examples, stoichiometry helps us understand the proportions in which substances react. By using the coefficients of reactants and products (numbers placed before the chemical formulas), we can determine how many moles of each substance are needed or produced. For instance, in the balanced equation for reaction (a), the coefficient 3 in front of Mg(OH)₂ indicates that three moles of magnesium hydroxide are produced for every one mole of magnesium nitride reacted.

Understanding stoichiometry is crucial for predicting the outcomes of reactions. It not only tells us what substances to expect but also informs us about the amounts required to achieve a desired chemical transformation, making it a powerful tool for scientists and industry professionals.

Chemical Reactions

Chemical reactions are processes in which substances, known as reactants, are transformed into different substances, known as products. Reactions can be classified into various types, such as synthesis, decomposition, single replacement, and double replacement, based on how atoms or ions exchange and reorganize throughout the process.

In the examples given, we see different types of chemical reactions. Synthesis occurs when two or more reactants combine to form a single product, such as the formation of nitrogen dioxide (NO₂) from nitric oxide (NO) and oxygen (O₂) in reaction (b). Decomposition involves a single compound breaking down into two or more simpler substances, which is not explicitly shown in these examples but is the opposite of synthesis.

To ensure chemical equations accurately represent these reactions, they must be balanced. This means the number of atoms for each element must be same on both the reactant and product sides of the equation. This reflects the law of conservation of mass, which states that mass cannot be created or destroyed in a chemical reaction.

Mole Concept

The mole concept is central to understanding chemical quantities. It relates the microscopic world of atoms and molecules to the macroscopic quantities that we can measure in a laboratory. A mole is defined as the amount of substance that contains the same number of entities (atoms, molecules, ions, or other particles) as there are atoms in 12 grams of carbon-12.

This number, known as Avogadro's number, is approximately 6.022 x 10²³. For example, when we state that we have 1 mole of NH₃, we are saying we have 6.022 x 10²³ molecules of ammonia. In stoichiometry, we often convert between moles and grams using the molar mass of substances, allowing us to measure out precise amounts of reactants for reactions.

Understanding the mole concept helps us to use balanced chemical equations to predict the mass of product that can be formed from a given mass of reactant, as well as to calculate the mass of a reactant needed to completely react with another reactant. This is particularly important when preparing solutions, such as reaction (d) between NH₃(aq) and H⁺(aq), ensuring the correct stoichiometry is maintained throughout the process.