SO42- + HAsO2+ 2H+H3AsO4 + SO2

1. In the above reaction, the oxidation state of sulfur changes from (Answer) to (Answer)

2. How many electrons are transferred in the reaction?

To determine the oxidation state of sulfur in the given reaction, you need to understand the rules for assigning oxidation numbers.

1. Rules for assigning oxidation numbers:
- The oxidation number of an atom in its uncombined state is always zero.
- The sum of the oxidation numbers in a neutral compound is always zero.
- In ions, the oxidation number is equal to the charge on the ion.
- Oxygen usually has an oxidation number of -2, except in peroxides where it is -1.
- Hydrogen usually has an oxidation number of +1, except in hydrides where it is -1.

Now, let's apply these rules to determine the oxidation state of sulfur in the given reaction.

1. Oxidation state of sulfur changes from (Answer) to (Answer):

The reactant SO42- has an oxidation state of +6 since each oxygen atom has a -2 oxidation state and there are four oxygen atoms in the sulfate ion. Similarly, HAsO2+ has an oxidation state of +3 since there are two oxygen atoms with a -2 oxidation state and one hydrogen atom with a +1 oxidation state.

In the product H3AsO4, the oxygen atoms have an oxidation state of -2, and since there are four oxygen atoms, the total oxidation state contributed by oxygen is -8. To balance out the charge, the arsenic atom in H3AsO4 must have an oxidation state of +5.

Finally, the product SO2 has a sulfur atom in the 4th oxidation state, which is 0. This is because oxygen has an oxidation state of -2, and since there are two oxygen atoms, the total oxidation state contributed by oxygen is -4. Consequently, the sulfur atom should have a +4 oxidation state to balance the charge.

Therefore, the oxidation state of sulfur changes from +6 to +4 in the given reaction.

2. To determine the number of electrons transferred in the reaction, you can compare the change in oxidation state of sulfur:

The change in oxidation state is +6 to +4, which means the sulfur atom gained two electrons.

Thus, two electrons are transferred in the reaction.