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Questions and Answers
What is the oxidation number of a Group 2A element in a compound?
What is the oxidation number of a Group 2A element in a compound?
Which of the following is NOT a characteristic of a reduction reaction?
Which of the following is NOT a characteristic of a reduction reaction?
Which of the following is an example of a strong acid?
Which of the following is an example of a strong acid?
What is the oxidation number of oxygen in oxygen fluorides?
What is the oxidation number of oxygen in oxygen fluorides?
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What is the oxidation number of hydrogen in metal hydrides?
What is the oxidation number of hydrogen in metal hydrides?
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What type of reaction involves the gain of one or more electrons?
What type of reaction involves the gain of one or more electrons?
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What is the oxidation number of a Group 17 element in a compound?
What is the oxidation number of a Group 17 element in a compound?
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Which of the following is an example of a weak acid?
Which of the following is an example of a weak acid?
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Study Notes
Oxidation Numbers
- Definition: A number assigned to an atom in a molecule that represents the number of electrons it has gained or lost.
- Rules for assigning oxidation numbers:
- Free elements have an oxidation number of 0.
- Monatomic ions have an oxidation number equal to their charge.
- In compounds, the oxidation number of a Group 1A element is +1, Group 2A element is +2, and a Group 17 element is -1.
- Hydrogen has an oxidation number of +1, except in metal hydrides where it is -1.
- Oxygen has an oxidation number of -2, except in peroxides where it is -1 and in oxygen fluorides where it is +2.
Reduction Reactions
- Definition: A reaction in which an atom, molecule, or ion gains one or more electrons.
- Characteristics:
- Involves a gain of electrons.
- Results in a decrease in oxidation number.
- Often accompanied by the loss of oxygen or the gain of hydrogen.
- Can be represented by the half-reaction:
Ox + e⁻ → Red
Strong Vs Weak Acids
-
Strong Acids:
- Completely dissociate in water to produce H₃O⁺ ions.
- Examples: HCl, HNO₃, H₂SO₄, HClO₃, and HClO₄.
- High acidity, low pH.
-
Weak Acids:
- Only partially dissociate in water to produce H₃O⁺ ions.
- Examples: HF, CH₃COOH, HCO₃⁻, and HPO₄²⁻.
- Low acidity, higher pH.
- Can be represented by the equilibrium:
HA + H₂O ⇌ H₃O⁺ + A⁻
Oxidation Numbers
- Oxidation numbers are assigned to atoms in a molecule to represent the number of electrons gained or lost.
- Free elements have an oxidation number of 0.
- Monatomic ions have an oxidation number equal to their charge.
- Group 1A elements have an oxidation number of +1 in compounds.
- Group 2A elements have an oxidation number of +2 in compounds.
- Group 17 elements have an oxidation number of -1 in compounds.
- Hydrogen has an oxidation number of +1, except in metal hydrides where it is -1.
- Oxygen has an oxidation number of -2, except in peroxides where it is -1 and in oxygen fluorides where it is +2.
Reduction Reactions
- Reduction reactions involve a gain of electrons.
- Reduction reactions result in a decrease in oxidation number.
- Reduction reactions often involve the loss of oxygen or the gain of hydrogen.
- Reduction reactions can be represented by the half-reaction:
Ox + e⁻ → Red.
Strong vs Weak Acids
Strong Acids
- Strong acids completely dissociate in water to produce H₃O⁺ ions.
- Examples of strong acids include HCl, HNO₃, H₂SO₄, HClO₃, and HClO₄.
- Strong acids have high acidity and low pH.
Weak Acids
- Weak acids only partially dissociate in water to produce H₃O⁺ ions.
- Examples of weak acids include HF, CH₃COOH, HCO₃⁻, and HPO₄²⁻.
- Weak acids have low acidity and higher pH.
- Weak acids can be represented by the equilibrium:
HA + H₂O ⇌ H₃O⁺ + A⁻.
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Description
Learn about the rules for assigning oxidation numbers to atoms in molecules, including free elements, monatomic ions, and compounds. Understand how to determine the oxidation number of different elements.
