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Questions and Answers
What is the oxidation state of each atom in the molecule Cl2?
What is the oxidation state of each atom in the molecule Cl2?
In the compound GeO2, what is the oxidation state of germanium (Ge)?
In the compound GeO2, what is the oxidation state of germanium (Ge)?
For the ionic compound CaCl2, what is the oxidation state of calcium (Ca)?
For the ionic compound CaCl2, what is the oxidation state of calcium (Ca)?
What is the total oxidation state for all atoms in the compound NaCl?
What is the total oxidation state for all atoms in the compound NaCl?
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In the polyatomic ion NO3–, what is the oxidation state of nitrogen (N)?
In the polyatomic ion NO3–, what is the oxidation state of nitrogen (N)?
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What occurs during the oxidation part of a redox reaction?
What occurs during the oxidation part of a redox reaction?
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In the reaction 2 Na(s) + Cl2(g) → 2 Na+ + 2 Cl–(s), which species acts as the oxidizing agent?
In the reaction 2 Na(s) + Cl2(g) → 2 Na+ + 2 Cl–(s), which species acts as the oxidizing agent?
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What type of reaction involves O2 as a reactant and releases a significant amount of energy?
What type of reaction involves O2 as a reactant and releases a significant amount of energy?
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Which statement best defines the oxidation number in a chemical process?
Which statement best defines the oxidation number in a chemical process?
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In the reaction 4 Na(s) + O2(g) → 2 Na2O(s), what do the Na atoms convert into?
In the reaction 4 Na(s) + O2(g) → 2 Na2O(s), what do the Na atoms convert into?
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Study Notes
Oxidation-Reduction Reactions
- Oxidation-reduction (redox) reactions involve electron transfer between reactants.
- Oxidation is the loss of electrons, while reduction is the gain of electrons.
- Examples include rusting of iron (4 Fe(s) + 3 O₂(g) → 2 Fe₂O₃(s)), combustion of octane (2 C₈H₁₈(l) + 25 O₂(g) → 16 CO₂(g) + 18 H₂O(g)), and combustion of hydrogen (2 H₂(g) + O₂(g) → 2 H₂O(g)).
- Sodium reacting with chlorine (2 Na(s) + Cl₂(g) → 2 NaCl(s)) is another example, where electrons transfer from sodium to chlorine.
Combustion as Redox
- Combustion reactions are a type of redox reaction where oxygen is a reactant.
- These reactions often release significant energy.
Combustion Reactions
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Reactions involving oxygen as a reactant are called combustion reactions.
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Combustion is a subclass of oxidation-reduction reactions.
Reactions of Metals with Nonmetals
- Reactions involving a metal reacting with a nonmetal often involve a conversion of free elements into ions.
- Examples given include 4 Na(s) + O₂(g) → 2 Na₂O(s) and 2 Na(s) + Cl₂(g) → 2 NaCl(s).
Oxidation and Reduction (Detailed)
- Atoms must gain or lose electrons to become ions in a redox reaction.
- Oxidation and reduction always occur together – one substance loses electrons while another gains them.
- When something loses electrons it undergoes oxidation and is called the reducing agent
- When something gains electrons it undergoes reduction and is called the oxidizing agent
Oxidation States
- Oxidation/reduction reactions also require a method to calculate how many electrons are transferred
- Chemists quantify this in reactions by assigning oxidation states to different elements in a reaction.
- Oxidation number: A positive or negative number assigned to an element to indicate its degree of oxidation/reduction in a substance based on rules.
Rules for Assigning Oxidation States
- Rule 1: Free elements have an oxidation state of 0 (e.g., Na = 0, Cl₂ = 0 in 2 Na(s) + Cl₂(g) → 2 NaCl(s))
- Rule 2: Monatomic ions have an oxidation state equal to their charge (e.g., Na = +1, Cl = -1 in NaCl)
- Rule 3: The sum of all oxidation states in a neutral compound equals 0. The sum of the oxidation states of all atoms in a polyatomic ion equals the charge on that ion. (e.g., Na=+1 and Cl=-1 in NaCl, (+1)+(-1)=0 or N=+5 and O=-2 in NO₃, (+5) +3(-2)=-1).
Further Examples of Oxidation Numbers, Oxidation, and Reduction
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Oxidation occurs when an atom's oxidation state increases during a reaction.
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Reduction occurs when an atom's oxidation state decreases during a reaction
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Example : Sn⁴⁺ + Ca → Sn²⁺ + Ca²⁺ (Ca is oxidized/reducing agent, Sn⁴⁺ is reduced/oxidizing agent)
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Another example : F₂ + S → SF₄ (S is oxidized/reducing agent, F₂ is reduced/oxidizing agent)
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Example: CH₄ + 2O₂ → CO₂ + 2H₂O (C is oxidized, O is reduced)
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Description
Test your knowledge on oxidation-reduction (redox) reactions, including the concept of electron transfer, and examples like combustion and metal-nonmetal reactions. Discover how these chemical processes play a crucial role in various reactions and their classification.
