Problem 241

Question

Iron (II) sulphide is heated in air to form compound \(' A^{\prime}\), an oxide of sulphur. Compound 'A' is dissolved in water to give an acid. The basicity of this acid is

Step-by-Step Solution

Verified
Answer
The basicity of the acid is 2.
1Step 1: Write the Reaction Equation for Heating
When iron (II) sulphide is heated in air, it reacts with oxygen to form iron (II) oxide and sulfur dioxide. The chemical equation for this reaction is: \[ 2FeS + 3O_2 \rightarrow 2FeO + 2SO_2 \] Here, \( SO_2 \) is identified as Compound 'A', an oxide of sulfur.
2Step 2: Dissolve Compound 'A' in Water
Sulfur dioxide \((SO_2)\) is dissolved in water to form sulfurous acid. The chemical equation for this dissolution is: \[ SO_2 + H_2O \rightarrow H_2SO_3 \] The compound formed after dissolving \( SO_2 \) in water is sulfurous acid \((H_2SO_3)\).
3Step 3: Determine the Basicity of the Acid
The basicity of an acid is determined by the number of hydrogen ions \((H^+)\) that it can donate. In the case of sulfurous acid \((H_2SO_3)\), it can donate two hydrogen ions, which makes it a dibasic acid. Thus, the basicity of sulfurous acid is 2.

Key Concepts

Iron (II) sulphideOxides of sulfurSulfurous acidChemical equationsAcid basicity
Iron (II) sulphide
Iron (II) sulphide, also known as ferrous sulfide, is a chemical compound with the formula \( FeS \). It appears as a black, solid material and is commonly used in various chemical reactions.
One of its significant reactions involves its exposure to oxygen or air.
This leads to its transformation into iron (II) oxide and sulfur dioxide. This transformation is especially important in understanding the behavior of sulfides in nature and various industrial processes.
  • Formula: \( FeS \)
  • Appearance: black solid
  • Molar mass: 87.91 g/mol
Understanding this compound helps in predicting the outcomes of chemical reactions involving sulfides and is critical for students learning about sulfur chemistry.
Oxides of sulfur
Oxides of sulfur are important compounds in both nature and industry.
The most common sulfur oxides are sulfur dioxide \( (SO_2) \) and sulfur trioxide \( (SO_3) \).
These compounds are formed when sulfur reacts with oxygen in the air. Sulfur dioxide, in particular, is a crucial intermediate in the production of sulfuric acid and can also lead to environmental concerns like acid rain.
Let's summarize:
  • \( SO_2 \) - Sulfur Dioxide, a colorless gas with a sharp odor
  • \( SO_3 \) - Sulfur Trioxide, a strong oxidizing agent
Sulfur dioxide is particularly important in this exercise, as it becomes involved in forming sulfurous acid when mixed with water.
Sulfurous acid
Sulfurous acid \( (H_2SO_3) \) is formed when sulfur dioxide \( (SO_2) \) is dissolved in water.
This compound is often used as a mild acidic agent and is noted for its role in wine preservation and bleaching processes.
Sulfurous acid is considered a weak acid as it is not often found in a pure state, existing typically in equilibrium with water and sulfur dioxide. Its uses include cleaning and disinfecting agents.
  • Formation equation: \( SO_2 + H_2O \rightarrow H_2SO_3 \)
  • Characteristics: weak acid, exists in equilibrium
Understanding sulfurous acid is key for grasping reactions involving oxidation and acid formation.
Chemical equations
Chemical equations are shorthand representations of chemical reactions.
They describe the reactants and products, along with their stoichiometric relationships.
For example, when iron (II) sulphide reacts with oxygen, the chemical equation is: \[ 2FeS + 3O_2 \rightarrow 2FeO + 2SO_2 \]
These equations are crucial for predicting the amounts of products formed from given reactants and for understanding the flow of chemical transformations.
By balancing chemical equations, we adhere to the law of conservation of mass, ensuring that the number of atoms of each element is the same on both sides of the equation.
  • Reactants: substances that start the reaction
  • Products: substances formed from the reaction
Mastering chemical equations is essential for any chemistry student.
Acid basicity
The basicity of an acid refers to the number of protons \( (H^+) \) it can donate.
In other words, it's the count of hydrogen ions released when acid molecules disassociate in a solution.
Sulfurous acid \( (H_2SO_3) \) has a basicity of 2, making it a dibasic acid. This means it can liberate two hydrogen ions in a chemical reaction.
Basicity is important in determining how an acid will behave in chemical reactions and is a key factor in titration and neutralization processes.
  • Monobasic acid: can donate one proton
  • Dibasic acid: can donate two protons
  • Tribasic acid: can donate three protons
Grasping the concept of basicity helps us understand the strength of acids and their behavior in solutions.