1st question:A voltaic cell is made up of mg2+/mg half-cell and fe3+/fe2+ half-cell. Which of the following statement are correct?
a.addition of water to the fe3+/fe2+ half-cell has no effect on cell emf.
b.increasing the temperature has no effect on the cell emf.
c.Addition of the aqueous naoh to mg2+/mg half-cell decreases the cell emf.
2nd question:Which of the enthalpy change of the following reactions can only be obtained by application of Hess' Law.
a.The hydration of anhydrous copper sulphate to form crystal of CuSo4.5H2O
b.The formation of methane from its elements
c.The combustion of glucose c6h12o6.
The Attempt at a Solution
1st question:I understand a is correct as water decreases concentration of both to the same extent.But i have no idea why b and c are wrong.
2nd question:The answer is both a and b are correct.But i know that enthalpy change of formation of methane can be obtained by calculating bond energy,so formation of methane can be obtained by other methods and not just Hess law!?