Ch.4 - Chemical Quantities & Aqueous ReactionsWorksheetSee all chapters
All Chapters
Ch.1 - Intro to General Chemistry
Ch.2 - Atoms & Elements
Ch.3 - Chemical Reactions
BONUS: Lab Techniques and Procedures
BONUS: Mathematical Operations and Functions
Ch.4 - Chemical Quantities & Aqueous Reactions
Ch.5 - Gases
Ch.6 - Thermochemistry
Ch.7 - Quantum Mechanics
Ch.8 - Periodic Properties of the Elements
Ch.9 - Bonding & Molecular Structure
Ch.10 - Molecular Shapes & Valence Bond Theory
Ch.11 - Liquids, Solids & Intermolecular Forces
Ch.12 - Solutions
Ch.13 - Chemical Kinetics
Ch.14 - Chemical Equilibrium
Ch.15 - Acid and Base Equilibrium
Ch.16 - Aqueous Equilibrium
Ch. 17 - Chemical Thermodynamics
Ch.18 - Electrochemistry
Ch.19 - Nuclear Chemistry
Ch.20 - Organic Chemistry
Ch.22 - Chemistry of the Nonmetals
Ch.23 - Transition Metals and Coordination Compounds

Solution: How many electrons does each oxygen atom gain during the course of this reaction? Oxydation of calcium metal by molecular oxygen.

Solution: How many electrons does each oxygen atom gain during the course of this reaction?Oxydation of calcium metal by molecular oxygen.

Problem

How many electrons does each oxygen atom gain during the course of this reaction?

A series of photographs shows the overall reaction of the reactants 2 Ca (solid) plus O2 (gas) going to the product 2 CaO (solid). In the first photograph, calcium (solid) is oxidized (loses electrons) while O2 is reduced (gains electrons). Solid calcium appears as a dull metal. In the second photograph, Ca2+ and O2- ions combine to form CaO (solid). Solid CaO appears a lustrous metal.


Oxydation of calcium metal by molecular oxygen.


Solution

We’re being asked to determine the number of electrons gained by oxygen in the oxidation of calcium metal by molecular oxygen.

2 Ca(s) + O2 (g) → CaO(s)


To do so, we need to identify the change in oxidation state for each element in the reaction. 

Recall the mnemonic for redox reactions:

Loss Electrons  Oxidation  Reducing Agent

Gain Electrons  Reduction  Oxidizing Agent


This means the element that gains electrons/reduced is the oxidizing agent while the element that loses electrons/oxidized is the reducing agent


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