During electrolysis of an acidic aqueous solution of an unknown metal ion Mⁿ⁺
CHEMISTRY · Single correct · AP · Chemistry · Thermodynamics and Electrochemistry · Thermodynamics and Electrochemistry
Problem
During electrolysis of an acidic aqueous solution of an unknown metal ion Mⁿ⁺, a student measures the charge passed and the mass of metal deposited to determine n. Vigorous bubbling is observed at the cathode throughout the experiment. Which statement best explains how this observation could affect the calculated value of n?
(a) The calculated n will be too small because some of the measured charge produces H₂ instead of reducing Mⁿ⁺.
(b) The calculated n will be too large because some of the measured charge produces H₂ instead of reducing Mⁿ⁺.
(c) The calculated n will be too small because rising hydrogen bubbles knock some deposited metal back into solution, lowering the measured mass.
(d) The calculated n will be unchanged because hydrogen evolution and metal deposition each require the same number of electrons per mole of product.