Problem 47 - Chemistry The Central Science In Si Units

Question

Write a balanced equation for each of the following reactions: (a) Sulfur dioxide reacts with water. (b) Solid zinc sulfide reacts with hydrochloric acid. (c) Elemental sulfur reacts with sulfite ion to form thiosulfate. (d) Sulfur trioxide is dissolved in sulfuric acid.

Step-by-Step Solution

Answer

(a) \( \text{SO}_2 + \text{H}_2\text{O} \rightarrow \text{H}_2\text{SO}_3 \); (b) \( \text{ZnS} + 2\text{HCl} \rightarrow \text{ZnCl}_2 + \text{H}_2\text{S} \); (c) \( \text{S} + \text{SO}_3^{2-} \rightarrow \text{S}_2\text{O}_3^{2-} \); (d) \( \text{SO}_3 + \text{H}_2\text{SO}_4 \rightarrow \text{H}_2\text{S}_2\text{O}_7 \).

Step 1: Identify Reactants and Products for Reaction (a)

In the reaction where sulfur dioxide reacts with water, the reactants are sulfur dioxide \( \text{SO}_2 \) and water \( \text{H}_2\text{O} \). The product formed is sulfurous acid \( \text{H}_2\text{SO}_3 \).

Step 2: Write Balanced Equation for Reaction (a)

The balanced chemical equation for sulfur dioxide reacting with water is: \[ \text{SO}_2 (g) + \text{H}_2\text{O} (l) \rightarrow \text{H}_2\text{SO}_3 (aq) \] This equation is already balanced as written.

Step 3: Identify Reactants and Products for Reaction (b)

In the reaction where solid zinc sulfide reacts with hydrochloric acid, the reactants are zinc sulfide \( \text{ZnS} \) and hydrochloric acid \( \text{HCl} \). The products are zinc chloride \( \text{ZnCl}_2 \) and hydrogen sulfide \( \text{H}_2\text{S} \).

Step 4: Write Balanced Equation for Reaction (b)

The balanced chemical equation is: \[ \text{ZnS} (s) + 2\text{HCl} (aq) \rightarrow \text{ZnCl}_2 (aq) + \text{H}_2\text{S} (g) \] This equation is balanced by having equal numbers of each type of atom on both sides.

Step 5: Identify Reactants and Products for Reaction (c)

The reaction involves elemental sulfur \( \text{S} \) reacting with sulfite ion \( \text{SO}_3^{2-} \) to form thiosulfate \( \text{S}_2\text{O}_3^{2-} \).

Step 6: Write Balanced Equation for Reaction (c)

The balanced equation is: \[ \text{S} (s) + \text{SO}_3^{2-} (aq) \rightarrow \text{S}_2\text{O}_3^{2-} (aq) \] Assure that sulfur atoms are balanced on both sides of the equation.

Step 7: Identify Reactants and Products for Reaction (d)

In the reaction where sulfur trioxide is dissolved in sulfuric acid, the reactants are sulfur trioxide \( \text{SO}_3 \) and sulfuric acid \( \text{H}_2\text{SO}_4 \). The product is oleum \( \text{H}_2\text{S}_2\text{O}_7 \).

Step 8: Write Balanced Equation for Reaction (d)

The balanced chemical equation is: \[ \text{SO}_3 (g) + \text{H}_2\text{SO}_4 (l) \rightarrow \text{H}_2\text{S}_2\text{O}_7 (l) \] This equation is balanced with equal numbers of each element on both sides.

Key Concepts

Understanding Chemical Reactions

Chemical reactions are the processes that transform substances into different substances. They are defined by the conversion of reactants into products. Each reaction involves breaking and forming of chemical bonds, which leads to a change in the chemical structure of the substances involved. For example, when sulfur dioxide reacts with water, the structure of the molecules changes to form sulfurous acid.
Understanding these transformations is key. Each reaction has a unique equation representing the transformation. The equation must be balanced to comply with the law of conservation of mass, meaning atoms must be neither created nor destroyed in the process.

• A chemical equation gives information about the reactants and products.
• Each side of the equation represents a different state of the reaction, showing molecules before and after the reaction.

Balancing chemical equations ensures that the same number of atoms for each element are present on both sides of the equation, maintaining balance and respecting the conservation law.

Role of Reactants and Products in a Reaction

In any chemical reaction, reactants are the starting substances that undergo change, while products are the new substances formed as a result. Identifying reactants and products is a crucial part of understanding reactions. This involves determining what substances you start with and what they turn into after the reaction occurs.
For instance, when solid zinc sulfide reacts with hydrochloric acid, the reactants are zinc sulfide and hydrochloric acid, forming zinc chloride and hydrogen sulfide as products. Recognizing these substances and their states is vital for writing and balancing chemical equations.

• Reactants are on the left side of the equation.
• Products are on the right side of the equation.
• Physical states of substances (solid, liquid, aqueous, or gas) are usually indicated using (s), (l), (aq), or (g).

Equations that reflect these transitions help chemists predict the outcome of reactions and measure reactants used or products formed.

The Basics of Stoichiometry

Stoichiometry is like the accounting system for chemical reactions. It involves using balanced chemical equations to calculate the quantities of reactants and products. By understanding stoichiometry, you can determine how much of each substance is needed or produced in a reaction.
This is done through mole-to-mole relationships derived from the balanced equation. For example, the reaction of elemental sulfur with sulfite ions to form thiosulfate ions requires calculating the precise amount of each reactant to use.

• Coefficients in a balanced equation show relative quantities of each substance.
• It allows conversion between moles of reactants and moles of products.
• Helps in determining yields and efficiencies of reactions.

Stoichiometry helps chemistry professionals and students alike to make precise calculations and predictions about chemical reactions. Understanding this allows for efficient use of resources and accurate forecasting of reaction outcomes.