Faraday’s constant, which relates coulombs to moles of electrons, can be used to calculate the approximate current available to the clock in this system. The current will not be constant because the H+ concentration (related to pH) is changing and also because the surface area and composition of the magnesium electrode change with time. The change is not necessarily regular, because although the surface is being oxidized, it is not smooth. The actual available surface area will therefore be considerably greater than the geometric surface. The mass of magnesium oxidized in the clock reaction over the 4hour period is approximately equal to the change in grams of magnesium while running the clock minus the mass of magnesium oxidized in orange juice without the clock. Using the data from Table 1,
grams Mg oxidized to run clock ≈ (0.3317 – 0.3089) – (0.3317 – 0.3136) = 0.0047 g Mg