2 mole of ideal gas at 27^oC temperature is expanded reversibly from 2 lit. to 20 lit. Find entropy change. (R = 2 cal/mol K)

Which reaction is not feasible?

Enthalpy of CH₄ + $${1 \over 2}$$ O₂ $$ \to $$ CH₃OH is negative. If enthalpy of combustion of CH₄ and CH₃OH are x and y respectively. Then which relation is correct?

Change in enthalpy for reaction,

2H₂O_2(l) $$ \to $$ 2H₂O_(l) + O_2(g)

if heat of formation of H₂O_2(l) and H₂O_(l) are $$-$$188 and - 286 kJ/mol respectively, is