Chapter 8: Problem 21
The difference in the oxidation numbers of the two types of sulphur atoms in \(\mathrm{Na}_{2} \mathrm{~S}_{4} \mathrm{O}_{6}\) is
Short Answer
Expert verified
The difference in oxidation numbers is 6.
Step by step solution
01
Determine Oxidation Rules
Identify the general rules to assign oxidation states: 1) The sum of oxidation numbers in a neutral compound must be zero; 2) The oxidation state of sodium (Na) is +1; 3) The oxidation state of oxygen (O) is -2.
02
Assign Known Oxidation States
For \(\mathrm{Na}_{2}\mathrm{~S}_{4}\mathrm{O}_{6} \), each Na has an oxidation number of +1 and each O has an oxidation number of -2. Since there are two Na atoms, their total contribution is \(+2\). For the six oxygen atoms, the total contribution is \(-12\).
03
Calculate Overall Charge Contribution
Combine the contributions of the known oxidation states. The positive contribution from sodium is +2, and the negative contribution from oxygen is -12. Thus, collectively, they contribute \(+2 - 12 = -10\).
04
Calculate Sum of Sulfur Contribution
Since the compound is neutral, the total oxidation number for sulfur atoms must offset the -10 from other atoms, making sulfur's total sum \(+10\).
05
Distribution of Oxidation Numbers Among Sulfur Atoms
We know sulfur can have multiple oxidation states in the same compound. Assign hypothetical oxidation numbers to sulfur atoms: two sulfur atoms in the center are likely to show a higher oxidation number due to more bonds with oxygen; they are often +5 each. The other two sulfur atoms, part of disulfide linkage (
-S-S-
), typically show oxidation states of -1 each.
06
Validate the Distribution
Validate the oxidation states: for sulfur atoms \(2 imes -1 = -2\) and \(2 imes +5 = +10\). The total for sulfur becomes \(-2 + 10 = +8\), this overall sulfur contribution complements \(-10\) from other atoms, confirming the structure balance to zero.
07
Calculate Difference in Oxidation Numbers
Subtract the oxidation number of disulfide sulfur atoms \((-1)\) from those bonded with more oxygens \((+5)\). The difference is \(+5 - (-1) = 6\).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Sulfur Oxidation State
When dealing with compounds like \(\mathrm{Na}_{2} \mathrm{~S}_{4} \mathrm{O}_{6}\), it's important to understand that sulfur can exist in multiple oxidation states within a single molecule. In this case, the sulfur atoms are involved in two different environments:
- The central sulfur atoms typically participate in numerous bonds involving oxygen, which often results in a higher oxidation state. For this compound, these central sulfur atoms are each assigned an oxidation state of +5.
- The sulfur atoms that form part of a disulfide linkage, represented as \(-\mathrm{S-S}-\), usually have fewer bonds with oxygen. Here, these atoms are typically assigned an oxidation state of -1.
Neutral Compound
A neutral compound is one where the total charge from all atoms is zero. This is a critical concept in chemistry because it helps in determining how oxidation numbers are distributed among the atoms in a molecule.
- In our example of \(\mathrm{Na}_{2} \mathrm{~S}_{4} \mathrm{O}_{6}\), this means the sum of the oxidation states of all sodium, sulfur, and oxygen atoms must be zero.
- For the conjunctive knowledge, sodium has a known oxidation state of +1, while oxygen typically exhibits an oxidation state of -2. Adding their contributions helps us establish the balance needed from sulfur atoms.
Oxidation Rules
Oxidation rules provide a systematic way to assign oxidation states to diverse elements in a compound, ensuring chemical equations are balanced and predictions about reactivity can be made. The key rules to consider include:
- The oxidation number of an element in its standard state is always zero.
- The sum of the oxidation states in a neutral compound must be zero.
- Sodium (\(\mathrm{Na}\)) typically takes an oxidation state of +1, owing to its single valence electron, which it donates during bonding.
- Oxygen almost always takes an oxidation state of -2, given its electronegative nature, causing it to gain electrons.