Question

Write the balanced chemical equations for (a) the complete combustion of acetic acid $\left({\mathrm{CH}}_3\mathrm{COOH}\right)$, the main active ingredient in vinegar; (b) the decomposition of solid calcium hydroxide into solid calcium (II) oxide (lime) and water vapor; (c) the combination reaction between nickel metal and chlorine gas.

Short answer

a) The balanced chemical equation for the complete combustion of acetic acid is: $$C{H}_{3}COOH+2O_2\to 2C{O}_2+2H_{2}O$$ b) The balanced chemical equation for the decomposition of calcium hydroxide is: $$Ca(OH{)}_2\to CaO+H_{2}O$$ c) The balanced chemical equation for the combination reaction between nickel metal and chlorine gas is: $$Ni+C{l}_2\to NiC{l}_2$$

Step-by-step solution

a) Complete combustion of acetic acid

To balance this chemical equation, we need to write the correct proportions of reactants and products to ensure that the number of atoms of each element is equal on both sides. We start with writing the unbalanced equation first: $$C{H}_{3}COOH+O_2\to C{O}_2+H_{2}O$$ Now, let's balance the chemical equation. We have 4 Hydrogen atoms, 2 Carbon atoms, and 2 Oxygen atoms in acetic acid. The balanced chemical equation for the combustion of acetic acid is: $$C{H}_{3}COOH+2O_2\to 2C{O}_2+2H_{2}O$$

b) Decomposition of calcium hydroxide

First, let's write the unbalanced equation: $$Ca(OH{)}_2\to CaO+H_{2}O$$ Now, we'll balance the chemical equation. Calcium and oxygen are already balanced. We only need to balance the hydrogen atoms. The balanced equation is: $$Ca(OH{)}_2\to CaO+H_{2}O$$ This balanced equation shows that one mole of calcium hydroxide decomposes to produce one mole of calcium (II) oxide and one mole of water vapor.

c) Combination reaction between nickel metal and chlorine gas

Let's start by writing the unbalanced equation: $$Ni+C{l}_2\to NiC{l}_2$$ The equation is already balanced, with one nickel atom reacting with one chlorine molecule to form one mole of nickel (II) chloride. The balanced chemical equation is: $$Ni+C{l}_2\to NiC{l}_2$$

Key concepts

Complete Combustion Reaction

Understanding the basics of a complete combustion reaction is essential for students delving into chemical equations. In a complete combustion process, a compound reacts with an excess of oxygen to produce carbon dioxide, water, and energy, usually in the form of heat. For example, acetic acid, the main ingredient in vinegar, combines with oxygen to form carbon dioxide and water. The chemical equation must be balanced to ensure mass conservation.
When balancing a combustion reaction equation, it's important to start by balancing the carbon (C) and hydrogen (H) atoms, then proceed to balance the oxygen (O) atoms. For acetic acid ${\mathrm{CH}}_3\mathrm{COOH}$, we initially have 2 carbon atoms and 4 hydrogen atoms. After reacting with oxygen $O_2$, we form 2 molecules of carbon dioxide $C{O}_2$ and 2 molecules of water $H_{2}O$. Balancing this equation involves ensuring that there are equal numbers of each type of atom on both sides of the equation.

Quick Tips for Balancing Combustion Reactions

• Count the number of carbon and hydrogen atoms in the fuel component.
• Ensure that every carbon atom in the compound turns into carbon dioxide.
• Make water molecules from the hydrogen atoms in the compound.
• Lastly, adjust the oxygen molecules to balance the equation.

Through these steps, we achieve the balanced chemical equation for the complete combustion of acetic acid: $$C{H}_{3}COOH+2O_2\to 2C{O}_2+2H_{2}O$$.

Decomposition Reaction

Decomposition reaction is another fundamental chemical process where a single compound breaks down into two or more simpler substances. Unlike combination reactions which build up complexity, decomposition reactions reduce it.
For instance, when solid calcium hydroxide decomposes, it splits into solid calcium oxide, commonly known as lime, and water vapor. The key to balancing a decomposition reaction is to compare the number of atoms in the reactant and the products. Initially, we observe the unbalanced equation $$Ca(OH{)}_2\to CaO+H_{2}O$$. Calcium and oxygen are already balanced; the final step is to ensure that the hydrogen atoms are balanced, which, in this case, they are from the start.
Decomposition reactions are critical in various applications, from the production of calcium oxide for industrial use to the breakdown of organic compounds.

Factors Affecting Decomposition Reactions

• Temperature: Higher temperatures usually speed up decomposition.
• Presence of catalysts: Certain substances can catalyze the reaction, making it proceed faster.
• Nature of the compound: Different compounds will decompose at different rates and under different conditions.

The balanced chemical equation for the decomposition of calcium hydroxide is thus: $$Ca(OH{)}_2\to CaO+H_{2}O$$, indicating the straightforward nature of this type of reaction.

Combination Reaction

A combination reaction, as the name suggests, involves two or more substances combining to form a single product. These reactions can be simple to balance as they often involve straightforward ratios of reactants to products.
Take, for example, the combination of nickel metal and chlorine gas. When these two reactants come together, they form nickel (II) chloride. The initial step is to write down the unbalanced equation: $$Ni+C{l}_2\to NiC{l}_2$$. After examining the equation, it's clear that the reactants and products are already in balance, with one nickel atom and two chlorine atoms on both sides of the reaction.
Combination reactions are common in the formation of compounds and can occur between elements, between compounds, or between an element and a compound. They are essential in synthesis processes in chemistry and industrial applications.

Understanding Combination Reactions

• Start by identifying the reactants and products.
• Check the valencies or combining capacities of the elements.
• Write the initial unbalanced equation with reactants and products.
• Balance the equation by making sure the number of atoms of each element is the same on both sides of the equation.

The balanced chemical equation for the combination of nickel and chlorine is given by: $$Ni+C{l}_2\to NiC{l}_2$$, illustrating the simplicity yet significance of combination reactions.