Oxidation Numbers for H3AsO4 and H2S Equation

In summary, the rules for oxidation numbers were discussed in the conversation. The oxidation numbers for oxygen and hydrogen were determined based on these rules. The oxidation numbers for arsenic and sulfur in the chemical equation were then figured out using the fact that the molecule must have a neutral charge. The final conclusion was that the oxidation number for sulfur is -2.
  • #1
Specter

Homework Statement


Identify the element oxidized and the element reduced, in this chemical equation:
H3AsO4+H2S ---> H3AsO3+S+H2O

Homework Equations


none

The Attempt at a Solution


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So I have learned the rules for oxidation numbers:

1. The oxidation number of an element is always 0 regardless of its subscript. This is true as long as they are not part of compound.
2. The oxidation number of a simple ion is the charge of the ion.
3.The oxidation number of oxygen in compounds is -2.
4. The oxidation number of hydrogen in compounds is +1.
5.Group 1 and group 2 metals always have a +1, and +2 value, respectively, in compounds.
6. All other oxidation numbers are assigned so that the net sum of the oxidation numbers equals the net charge of the molecule or complex ion.

So with what I know I can figure out the oxidation numbers for the oxygens and hydrogens in the chemical equation but how do I figure out the numbers for arsenic and sulfur?
 
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  • #2
So let's start with H2S. It has no net charge, so you can apply rules 6 and 4.
 
  • #3
DrDu said:
So let's start with H2S. It has no net charge, so you can apply rules 6 and 4.
H2 would be +1 but I'm not sure what S would be. Would it be -2 so that it equals +1 overall?
 
  • #4
Specter said:
H2 would be +1 but I'm not sure what S would be. Would it be -2 so that it equals +1 overall?

No, H2 would be not +1. You have two H at +1 each, so it is +2 total for hydrogen. If so, what must be the charge on the sulfur atom so that the molecule is neutral?
 
  • #5
Borek said:
No, H2 would be not +1. You have two H at +1 each, so it is +2 total for hydrogen. If so, what must be the charge on the sulfur atom so that the molecule is neutral?
Oh I understand. Thats why S is -2.
 
  • #6
Specter said:
Oh I understand. Thats why S is -2.

That's it.
 

FAQ: Oxidation Numbers for H3AsO4 and H2S Equation

What is the oxidation number of arsenic in H3AsO4?

The oxidation number of arsenic in H3AsO4 is +5. This is because oxygen has an oxidation number of -2 and hydrogen has an oxidation number of +1, so the overall charge of the compound (H3AsO4) must be neutral and therefore the arsenic must have an oxidation number of +5 to balance out the charges.

What is the oxidation number of sulfur in H2S?

The oxidation number of sulfur in H2S is -2. This is because hydrogen has an oxidation number of +1 and the overall charge of the compound (H2S) is neutral, so sulfur must have an oxidation number of -2 to balance out the charges.

How do you determine oxidation numbers in a compound?

To determine the oxidation numbers in a compound, you must follow a set of rules. First, all elements in their elemental form have an oxidation number of 0. Second, the sum of all oxidation numbers in a neutral compound must be 0. Third, the sum of all oxidation numbers in a polyatomic ion must equal the charge of the ion. Fourth, hydrogen has an oxidation number of +1 and oxygen has an oxidation number of -2 in most compounds. Fifth, the more electronegative element in a compound is assigned a negative oxidation number equal to its charge in a monatomic ion. Sixth, the sum of all oxidation numbers in a neutral compound must be equal to the overall charge of the compound.

What is the oxidation number of hydrogen in H3AsO4?

The oxidation number of hydrogen in H3AsO4 is +1. This is because the overall charge of the compound must be neutral and arsenic has an oxidation number of +5, so the three hydrogen atoms must have a combined oxidation number of +3 to balance out the charges. Each hydrogen atom has an oxidation number of +1 in order to achieve this.

How do you balance an equation involving oxidation numbers?

To balance an equation involving oxidation numbers, you must ensure that the total oxidation number of each element in the reactants equals the total oxidation number of each element in the products. To achieve this, you may need to adjust the coefficients of the reactants and products. Additionally, be sure to follow the rules for assigning oxidation numbers to each element in the compound. Balancing equations involving oxidation numbers can be tricky, so it's important to practice and understand the rules thoroughly.

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