A solution of an unknown divalent metal ion, M²⁺, is electrolyzed with a steady current of 0.750 A for 25.0 min. The cathode gains 0.843 g of the metal. Based on these data, what is the best estimate of the molar mass of the metal?
a) 73g mol−1
b) 290g mol−1
c) 145g mol−1
d) 97g mol−1