Chapter 21: Problem 16
Write a balanced net ionic equation for (a) the oxidation of iodide to iodine by sulfate ion in acidic solution. Sulfur dioxide gas is also produced. (b) The preparation of iodine from an iodide salt and chlorine gas.
Short Answer
Expert verified
Answer:
(a) 2 I^- + SO4^2- + 2 H^+ → I2 + SO2 + 2 H2O
(b) 2 I^- + Cl2 → I2 + 2 Cl^-
Step by step solution
01
Write Unbalanced Equation
Write the unbalanced equation involving the reactants and products.
2 I^- + SO4^2- → I2 + SO2
02
Balance the atoms
The number of Iodine atoms is balanced. But for the Sulfur and Oxygen atoms, we can add water molecules (H2O) to balance the oxygen atoms and add hydrogen ions (H^+) to balance the hydrogen atoms.
2 I^- + SO4^2- + 2 H^+ → I2 + SO2 + 2 H2O
03
Write the balanced net ionic equation
Since no spectator ions are present in the reaction, the equation we obtained in the previous step is already a net ionic equation. The balanced net ionic equation is:
2 I^- + SO4^2- + 2 H^+ → I2 + SO2 + 2 H2O
(b) Preparation of iodine from an iodide salt and chlorine gas
04
Write Unbalanced Equation
Write the unbalanced equation involving the reactants and products. The iodide salt reacts with chlorine gas (Cl2) to produce iodine (I2).
2 I^- + Cl2 → I2 + 2 Cl^-
05
Balance the atoms
All atoms (Iodine, Chlorine) are balanced in the equation, and there are no other atoms involved.
06
Write the balanced net ionic equation
Now, write the balanced net ionic equation. As there are no spectator ions in this reaction, the equation we have is the net ionic equation:
2 I^- + Cl2 → I2 + 2 Cl^-
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Redox Reactions
Redox reactions, short for reduction-oxidation reactions, are fundamental chemical processes involving the transfer of electrons between two species. They are crucial in many chemical and biological processes, including the reactions described in the exercise: the oxidation of iodide to iodine and the reaction of iodide with chlorine.
In redox reactions, two half-reactions occur simultaneously:
In redox reactions, two half-reactions occur simultaneously:
- Oxidation: Loss of electrons. For example, iodide ions ( I^-) lose electrons to form iodine ( I_2).
- Reduction: Gain of electrons. In the given exercise, sulfate ions (SO_4^{2-}) gain electrons to form sulfur dioxide ( SO_2) in one reaction, and chlorine gas ( Cl_2) gains electrons to form chloride ions ( Cl^-) in another.
Chemical Equation Balancing
Balancing chemical equations is essential in ensuring the reactants and products in a chemical reaction are accounted for according to the conservation of matter. In the original exercise, we balanced the chemical equations for redox reactions.
Stepwise balancing involves:
Stepwise balancing involves:
- Balancing atoms of each element on both sides of the equation by adjusting coefficients. This can include adding water (H_2O) molecules to balance oxygen and adding hydrogen ions (H^+) to balance hydrogen, especially pertinent when reactions occur in acidic solutions.
- Ensuring that the total charge is balanced between reactants and products. In redox reactions, this means making sure that the total electron transfer is equal and opposite for oxidation and reduction processes.
Acidic Solution Reactions
Acidic solution reactions, like those presented in the exercise, often require special steps to ensure the reaction correctly reflects the conditions under which it proceeds. Acidic conditions typically involve the presence of excess
H^+ ions, which can play an active role in balancing chemical equations.
When balancing redox reactions in acidic solutions, consider:
When balancing redox reactions in acidic solutions, consider:
- Additional H^+ ions are often involved in reactions that need to balance hydrogen atoms.
- Water molecules ( H_2O) may balance oxygen atoms, as in the oxidation of iodide by sulfate where water forms as a product.