In which of the following reactions H₂O₂ acts as a reducing agent?
1. H₂O₂ + 2H⁺ + 2e^- $$\to$$ 2H₂O
2. H₂O₂ - 2e^- $$\to$$ O₂ + 2H⁺
3. H₂O₂ + 2e^- $$\to$$ 2OH^-
4. H₂O₂ + 2OH^- - 2e^- $$\to$$ O₂ + 2H₂O

For the reaction SO₂ (g) + $${1 \over 2} O_2(g) \leftrightharpoons$$ SO₃(g).
if K_P = K_C(RT)^x where the symbols have usual meaning then the value of x is: (assuming ideality)

For complete combustion of ethanol, C₂H₅OH(l) + 3O₂(g) $$\to$$ 2CO₂(g) + 3H₂O(l) the amount of heat produced as measured in bomb calorimeter, is 1364.47 kJ mol^–1 at 25^oC. Assuming ideality the Enthalpy of combustion, $$\Delta _CH$$, for the reaction will be : (R = 8.314 kJ mol^–1)

Given below are the half-cell reactions:

Mn²⁺ + 2e^- $$\to$$ Mn; E^o = -1.18 V

2(Mn³⁺ + e^- $$\to$$ Mn²⁺); E^o = +1.51 V

The E^o for 3Mn²⁺ $$\to$$ Mn + 2Mn³⁺ will be :