Question

Write balanced chemical equations to correspond to each of the following descriptions: (a) Solid calcium carbide, \(\mathrm{CaC}_{2}\), reacts with water to form an aqueous solution of calcium hydroxide and acetylene gas, \(\mathrm{C}_{2} \mathrm{H}_{2}\). (b) When solid potassium chlorate is heated, it decom-

Short answer

(a) \(CaC_2 (s) + 2H_2O (l) \rightarrow Ca(OH)_2 (aq) + C_2H_2 (g)\) (b) \(2KClO_3 (s) \rightarrow 2KCl (s) + 3O_2 (g)\) (c) \(2HCl (aq) + CaCO_3 (s) \rightarrow H_2O (l) + CO_2 (g) + CaCl_2 (aq)\)

Step-by-step solution

(Equation (a): Calcium Carbide and Water Reaction)

Let's write the chemical equation for the reaction between solid calcium carbide, CaC2, and water, which produces an aqueous solution of calcium hydroxide and acetylene gas, C2H2. The reaction can be written as: CaC2 (s) + H2O (l) -> Ca(OH)2 (aq) + C2H2 (g) However, we need to balance this equation to ensure the number of atoms for each element is the same on both sides: CaC2 (s) + 2H2O (l) -> Ca(OH)2 (aq) + C2H2 (g) Now, the number of atoms for each element is balanced in the equation.

(Equation (b): Decomposition of Potassium Chlorate)

For the second description, solid potassium chlorate decomposes when heated to form solid potassium chloride and diatomic oxygen gas. We can write this chemical equation as follows: 2KClO3 (s) -> 2KCl (s) + 3O2 (g) This equation is now balanced, with equal numbers of atoms for each element on both sides of the equation.

(Equation (c): Hydrochloric Acid and Calcium Carbonate Reaction)

Finally, let's analyze the third description and write a balanced chemical equation for the reaction between a solution of hydrochloric acid and solid calcium carbonate, which produces water, carbon dioxide, and calcium chloride. The reaction can be written as: HCl (aq) + CaCO3 (s) -> H2O (l) + CO2 (g) + CaCl2 (aq) We must balance this equation to match the number of atoms of each element on both sides: 2HCl (aq) + CaCO3 (s) -> H2O (l) + CO2 (g) + CaCl2 (aq) The balanced chemical equations for each of the given descriptions are: (a) CaC2 (s) + 2H2O (l) -> Ca(OH)2 (aq) + C2H2 (g) (b) 2KClO3 (s) -> 2KCl (s) + 3O2 (g) (c) 2HCl (aq) + CaCO3 (s) -> H2O (l) + CO2 (g) + CaCl2 (aq)

Key concepts

Balanced Equation

A balanced chemical equation ensures that the number of atoms of each element is the same on both the reactants and products side. This reflects the law of conservation of mass, which states that matter cannot be created or destroyed in a chemical reaction. When we have a chemical reaction, it's crucial to depict it with a balanced equation.

For instance, when writing the equation for the reaction between calcium carbide and water, initially, it might not be balanced. By adjusting coefficients in front of compounds, we ensure both sides have equal numbers of each atom.

• Identify each of the elements involved.
• Count the number of atoms of each element present on both sides of the reaction.
• Add coefficients where necessary to balance the atoms on each side.

Using the steps above keeps chemical equations realistic and true to physical laws.

Calcium Carbide Reaction

When solid calcium carbide, represented by the chemical formula \(\mathrm{CaC}_{2}\), reacts with water, it forms calcium hydroxide and acetylene gas. This reaction is particularly interesting due to its applications, such as in generating acetylene gas for industrial purposes.

The chemical reaction can initially be expressed as:
\[ \text{CaC}_2 \,(s) + \text{H}_2\text{O} \,(l) \rightarrow \text{Ca(OH)}_2 \,(aq) + \text{C}_2\text{H}_2 \,(g) \]

However, balance is key, leading us to modify the water coefficient to ensure perfect balance:
\[ \text{CaC}_2 \,(s) + 2\text{H}_2\text{O} \,(l) \rightarrow \text{Ca(OH)}_2 \,(aq) + \text{C}_2\text{H}_2 \,(g) \]

Here, calcium carbide is transformed, emphasizing the concept of bond transformations in chemical reactions.

Potassium Chlorate Decomposition

Potassium chlorate decomposition is a classic example of a thermal decomposition reaction. When potassium chlorate \(\text{KClO}_3\) is heated, it breaks down to produce potassium chloride and oxygen gas. This reaction is noteworthy for its role in laboratory experiments and oxygen supply.

The heat driven decomposition can be portrayed through the equation:
\[ 2 \text{KClO}_3 \,(s) \rightarrow 2 \text{KCl} \,(s) + 3 \text{O}_2 \,(g) \]

Why do we need to balance it? Because each part of the reaction must comply with the conservation of mass. In this scenario,

• The number of potassium \(\text{K}\), chlorine \(\text{Cl}\), and oxygen \(\text{O}\) atoms remains constant.
• Oxygen molecules are consumed and generated threefold to match both atom balance and real conditions.

Understanding such reactions helps in grasping the creation of diatomic gases from compounds.

Hydrochloric Acid and Calcium Carbonate Reaction

The reaction between hydrochloric acid \(\text{HCl}\) and calcium carbonate \(\text{CaCO}_3\) is a fascinating process resulting in the formation of water, carbon dioxide, and calcium chloride. This reaction is a staple in chemistry for studying acid-base interactions and gas evolution reactions.

Initially, the equation can be outlined as:
\[ \text{HCl} \,(aq) + \text{CaCO}_3 \,(s) \rightarrow \text{H}_2\text{O} \,(l) + \text{CO}_2 \,(g) + \text{CaCl}_2 \,(aq) \]

To ensure accuracy, we need to balance the elements by adjusting the coefficients:
\[ 2 \text{HCl} \,(aq) + \text{CaCO}_3 \,(s) \rightarrow \text{H}_2\text{O} \,(l) + \text{CO}_2 \,(g) + \text{CaCl}_2 \,(aq) \]

Here, the double coefficient of hydrochloric acid ensures that hydrogen and chloride atoms are matched on both sides, demonstrating precise stoichiometric balance. This kind of reaction is vital in educational settings to illustrate the formation of gases and neutral compounds.