An electrolysis cell that deposits gold (from Au⁺ ions) operates for 15.0 minutes at a current of 2.30 a. What mass of gold is deposited?

Strategy 

As in any stoichiometry problem we need a balanced chemical equation, so we will start by writing the half-reaction for gold reduction. To determine the mass of gold deposited, we must calculate the number of moles of electrons used from the current and the time. We can use the half-reaction to obtain a mole ratio and convert moles of electrons into moles of gold. Once we have moles of gold, we convert to mass using the molar mass, as we have done many times in stoichiometry problems.