Podcast Beta
Questions and Answers
The oxidation number of an elemental substance is ______.
zero
For elements of Group I, the oxidation number is ______.
+1
Oxidation is defined as ______ loss.
electron
A redox reaction involves both oxidation and ______.
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The oxidising agent ______ electrons.
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In the reaction 2Mg + O2 → 2MgO, magnesium is ______.
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For oxygen, the oxidation number is typically ______.
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In the half-reaction, ______ is a reducing agent.
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To balance O atoms in half-reactions, one should add ______.
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Electrons are added to balance the ______ charges in half-reactions.
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To check the equation is balanced, compare the number of each ______ and the overall charge on each side.
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The half-reaction for potassium permanganate is represented by ______.
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In a basic solution redox reaction, you add the same number of ______ ions to both sides as there are H+ in each half-reaction.
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Combining H+ and OH– forms ______.
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The unbalanced reaction involves ______ metal and nitrate ions.
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The balanced reaction of zinc with nitrate is: 4Zn + 7OH– + NO3– + 6H2O → 4Zn(OH)42– + ______.
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Zinc can reduce ______+, but not the other way around.
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After step 5 in balancing, ensure water (H2O) is present on both sides of each ______.
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In the basic solution steps, 2MnO4– + H2O + Br– → 2MnO2 + 2OH– + ______–.
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To ensure the balanced reaction is correct, check that the number of each reactant and product ______ are equal.
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Study Notes
Oxidation Numbers
- The effective charge of an atom is represented by its oxidation number.
- The oxidation number of an elemental substance is always zero.
- The oxidation number of a monoatomic ion is equivalent to the charge number of that ion.
- The sum of oxidation numbers of all atoms in a species equals its total charge.
- Elements in their elemental form have an oxidation number of 0.
Assigning Oxidation Numbers
- For elements in Group I, the oxidation number is +1.
- For elements in Group II, the oxidation number is +2.
- For elements in Group III (excluding Boron), the oxidation number is +3 for M3+ and +1 for M+.
- For elements in Group IV (excluding Carbon and Silicon), the oxidation number is +4 for M4+ and +2 for M2+.
- For Hydrogen, the oxidation number is +1 when combined with non-metals and -1 when combined with metals.
- For Fluorine, the oxidation number is always -1 in all its compounds.
- For Oxygen, the oxidation number is -2 unless combined with Fluorine. It is -1 in peroxides (O22-), -½ in superoxides (O2-), and -⅓ in ozonides (O3-).
Redox Reactions
- Oxidation involves the loss of electrons, while reduction involves the gain of electrons.
- A redox reaction is a reaction where both oxidation and reduction occur simultaneously.
- An oxidizing agent removes electrons and becomes reduced in a reaction. The element within the oxidizing agent experiences a decrease in oxidation number.
- A reducing agent supplies electrons and becomes oxidized in a reaction. The element within the reducing agent experiences an increase in oxidation number.
Redox Reactions in Acidic Solution
- The balancing of redox reactions in acidic solution follows a specific set of steps:
- Identify the oxidized and reduced species based on oxidation number changes.
- Separate the reaction into two skeletal half-reactions.
- Balance all elements except O, H, and the charge by inspection.
- Balance oxygen atoms by adding H2O to each half-reaction.
- Balance hydrogen atoms by adding H+ to each half-reaction.
- Balance the electric charges in each half-reaction by adding electrons.
- Ensure the number of electrons in both half-reactions is equal by multiplying them by appropriate factors.
- Combine the two balanced half-reactions by adding them together, simplifying common species where possible.
- Verify the final equation is balanced by checking the number of each atom and the overall charge on both sides.
Redox Reactions in Basic Solution
- To balance redox reactions in basic solution, follow the steps for acidic solutions with these additional steps between Step 5 and 6:
- After balancing hydrogen atoms with H+, add the same number of OH- ions to both sides of each half-reaction.
- Combine H+ and OH- ions to form H2O.
- If H2O is present on both sides of the half-reactions, move it to one side.
- Continue with the remaining steps from the acidic solution procedure.
Element Activity Series
- An element activity series is a list of elements arranged in order of their reactivity.
- A metal can reduce the cations formed by any of the metals below it in the series.
- For example, Zinc (Zn) can reduce Cu2+ but not vice versa.
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Description
Test your understanding of oxidation numbers in chemistry with this quiz. Learn how to assign oxidation numbers to various elements and compounds based on their groups in the periodic table. This quiz covers the fundamental rules and principles of oxidation states.
