Chapter 14: Problem 16
Identify what is being oxidized and reduced in this redox reaction by assigning oxidation numbers to the atoms. $$ \mathrm{Sr}+\mathrm{SO}_{3} \rightarrow \mathrm{SrSO}_{3} $$
Short Answer
Expert verified
Strontium (Sr) is oxidized, and Sulfur (S) is reduced.
Step by step solution
01
Identify the Elements
Examine the reaction \( \mathrm{Sr} + \mathrm{SO}_3 \rightarrow \mathrm{SrSO}_3 \). The elements involved are Strontium (\( \mathrm{Sr} \)) and the components of \( \mathrm{SO}_3 \), which are Sulfur (\( \mathrm{S} \)) and Oxygen (\( \mathrm{O} \)).
02
Assign Oxidation Numbers to Reactants
Assign oxidation numbers for each element in the reactants.\( \mathrm{Sr} \) is a free element with an oxidation number of 0. In \( \mathrm{SO}_3 \), \( \mathrm{O} \) has an oxidation number of -2. With three oxygens, this contributes \( -6 \) in total. To balance this, \( \mathrm{S} \) must have an oxidation number of +6.
03
Assign Oxidation Numbers to Product
For the compound \( \mathrm{SrSO}_3 \), we know \( \mathrm{Sr} \) is a Group 2 element, typically having an oxidation number of +2. The \( \mathrm{SO}_3 \) group within the compound needs to counterbalance this. Since \( \mathrm{O} \) still has an oxidation number of -2, totaling \( -6 \) for three oxygens, the \( \mathrm{S} \) must still be +4 to balance the overall charge in the compound.
04
Determine Change in Oxidation Numbers
Compare the oxidation numbers in reactants and products:- \( \mathrm{Sr} \) changes from 0 to +2, thus is oxidized.- Sulfur’s oxidation number changes from +6 to +4, thus is reduced.
05
Identify Oxidized and Reduced Elements
From the oxidation number changes:- Strontium (\( \mathrm{Sr} \)) is oxidized because it loses electrons (oxidation number increases).- Sulfur (\( \mathrm{S} \)) is reduced because it gains electrons (oxidation number decreases).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Oxidation Number
The oxidation number is a way to keep track of electrons in a chemical reaction. It can be thought of as an 'electron bookkeeping' system. Each element in a compound or molecule is assigned an oxidation number to show the number of electrons it either gains or loses when forming a compound.
- Free elements, like plain Strontium (\( \mathrm{Sr} \)), have an oxidation number of 0 because they are not combined with other elements.
- In compounds, oxygen typically has an oxidation number of -2. If there are three oxygen atoms, as in \( \mathrm{SO}_{3} \), the total contribution from oxygen is \(-6\)
- To find the oxidation number of sulfur in \( \mathrm{SO}_{3} \), consider that the total charge of neutral compound is 0; therefore, Sulfur must be \(+6\) to balance the \(-6\) from oxygen.
- In contrast, in the compound \( \mathrm{SrSO}_{3} \), Strontium takes on its typical Group 2 oxidation number of \(+2\), while sulfur must adjust to \(+4\) so the overall charge remains neutral when combined with the \(-6\) from oxygen.
Oxidation
Oxidation is a process where an element loses electrons during a chemical reaction. When an element's oxidation number increases, it signifies that the element is oxidized.
- An easy way to remember this concept is through the mnemonic "OIL RIG" which stands for "Oxidation Is Loss" (of electrons).
- In the redox reaction given (\( \mathrm{Sr} + \mathrm{SO}_3 \rightarrow \mathrm{SrSO}_3 \)), Strontium (\( \mathrm{Sr} \)) is oxidized. Its oxidation number changes from 0 to +2.
- This positive change indicates that Sr loses two electrons.
Reduction
Reduction is the gain of electrons by an element during a chemical reaction. When an element's oxidation number decreases, it signifies that the element is reduced.
- The second part of the mnemonic "OIL RIG"—"Reduction Is Gain"—helps students remember that reduction involves gaining electrons.
- In the given reaction of \( \mathrm{Sr} + \mathrm{SO}_3 \rightarrow \mathrm{SrSO}_3 \), Sulfur (\( \mathrm{S} \)) is reduced.
- Sulfur's oxidation number decreases from +6 in \( \mathrm{SO}_{3} \) to +4 in \( \mathrm{SrSO}_{3} \), indicating a gain of electrons.