Explanation:

To calculate the oxidation state of an atom in a compound, you can:

1. Assign both electrons in each bond to the more electronegative atom of that bond. If the atoms are the same, then assign one electron to each.

2. Subtract the number of electrons assigned to each atom from the number of valence electrons in its neutral state. The result is the oxidation state of that atom.

3. Check that the sum of the oxidation states of all the atoms or ions in a neutral compound is zero, or equal to the charge on the ion ¹.

For example, let's calculate the oxidation state of carbon in C4H10:

- Carbon has 4 valence electrons.

- Each hydrogen has 1 valence electron.

- The C-H bond is considered polar covalent with carbon being slightly more electronegative than hydrogen. Therefore, we assign both electrons in each bond to carbon.

- For C4H10, we have 4 carbons and 10 hydrogens. The total number of valence electrons for carbons is 16 (4 x 4) and for hydrogens is 10 (10 x 1).

- We assign 8 electrons (2 per bond) to carbon from C-H bonds.

- The remaining 8 valence electrons are assigned to carbon from C-C bonds.

- The total number of electrons assigned to carbon is 16 (8 from C-H bonds and 8 from C-C bonds).

- The number of valence electrons in its neutral state is 4.

- Therefore, the oxidation state of carbon in C4H10 is -2.

Now let's calculate the standard EMF of cell for C4H10 + 13/2 O2 = 4CO2 + 5H2O:

- First, we need to balance the equation by multiplying C4H10 by 13/2 and H2O by 5:

C4H10 + 13/2 O2 = 4CO2 + 5H2O

13/2 C4H10 + 65/2 O2 = 20CO2 + 25H2O

- The standard EMF of cell can be calculated using Nernst equation:

Ecell = E°cell - (RT/nF)lnQ

where E°cell is standard EMF of cell under standard conditions, R is gas constant (8.314 J/K.mol), T is temperature in Kelvin (298 K), n is number of moles of electrons transferred (in this case n=20), F is Faraday constant (96485 C/mol), and Q is reaction quotient.

- We can calculate Q using concentrations at standard conditions:

Q = [CO2]^4[H2O]^5/[C4H10]^(13/2)[O2]^(65/2)

- We can use Gibbs free energy change (ΔG°) to calculate E°cell:

ΔG° = -nFE°cell

where ΔG° is Gibbs free energy change under standard conditions and F is Faraday constant (96485 C/mol).

Given ΔG° = -2746 J/mol , we can calculate E°cell as follows:

E°cell = ΔG°/(nF)

E°cell = (-2746 J/mol)/(20 x 96485 C/mol)

E°cell = -0.00142 V

Therefore, the standard EMF of cell for C4H10 + 13/2 O2 = 4CO2 + 5H2O is -0.00142 V.

I hope this helps!