Calculate oxidation number of S in {{H}_{2}}{{S}_{2}}{{O}_{7}} .

To calculate the oxidation number of sulfur (S) in {{H2S2O7}}, you can use the following steps:

Assign oxidation numbers to hydrogen (H) and oxygen (O) based on their typical oxidation states. Hydrogen is usually +1, and oxygen is typically -2 in most compounds.

The sum of the oxidation numbers in a molecule must equal its overall charge. In the case of {{H2S2O7}}, there is no overall charge given, so we assume it is neutral (0).

Calculate the oxidation number for sulfur (S) using the equation:

Sum of oxidation numbers of all atoms in the molecule = 0

Let x be the oxidation number of sulfur (S).

2(+1) + 2x + 7(-2) = 0

Now, simplify the equation:

2 + 2x - 14 = 0

Combine like terms:

2x - 12 = 0

Solve for x:
2x = 12

x = 12 / 2

x = 6

So, the oxidation number of sulfur (S) in {{H2S2O7}} is +6.