The overall reaction for the electrolysis of molten sodium chloride, 2 NaCll →electric current 2 Nal+Cl2gcan be expressed as two separate, simultaneous redox processes (Reactions 1 and 2) :
2 Cl-→ Cl2g+2 e-Reaction 1
2 Na++2 e-→2 NalReaction 2What is the amount of electric charge required to produce 0.80 mol of Na(l) during the electrolysis?

Question

The overall reaction for the electrolysis of molten sodium chloride,

2 NaCll →electric current 2 Nal+Cl2gcan be expressed as two separate, simultaneous redox processes (Reactions 1 and 2) :

2 Cl-→ Cl2g+2 e-Reaction 1

2 Na++2 e-→2 NalReaction 2What is the amount of electric charge required to produce 0.80 mol of Na(l) during the electrolysis?

Quizplus · Accepted Answer

11ecba2d_124a_f64b_a3bf_a7e472d4e02e_MD0008_00 An electrolytic cell can be conceptualized as a galvanic (voltaic) cell that is operating in reverse. In an electrolytic cell, electric current from an external source (such as a battery) is supplied to drive a nonspontaneous, endergonic chemical reaction (ΔG > 0). The operation of an electrolytic cell causes electrolysis, which is the electrochemical decomposition of a compound. During electrolysis, electron-rich species (such as anions) are oxidized at the electron-deficient anode. For example, in the electrolysis of molten NaCl, Cl⁻ is oxidized to Cl₂ gas (Reaction 1). Conversely, electron-deficient species (such as metal cations) are reduced at the electron-rich cathode. In the example of the electrolysis of molten NaCl, Na⁺ is reduced to Na metal (Reaction 2). The net reaction for these simultaneous processes results in a decomposition reaction. Based on the mole ratios obtained from the stoichiometric coefficients of the overall balanced reaction, the number of moles of NaCl(s) that must undergo electrolysis to form 0.80 mol Na(l) is given by: 11ecba2d_124a_f64c_a3bf_39987755519e_MD0008_00 Reactions 1 and 2 show that 2 moles of electrons are required for every 2 moles of NaCl(l) that undergo electrolysis. Consequently, the electrolysis of 0.80 mol NaCl(l) requires: 11ecba2d_124b_1d5d_a3bf_e9f310c0c6fa_MD0008_00 The charge used during electrolysis can be measured in a unit called the faraday, where 1 faraday equals the electric charge present in 1 mole of electrons. Accordingly, the number of faradays present in 0.80 mol e⁻ is: 11ecba2d_124b_1d5e_a3bf_dd48565623ec_MD0008_00 Therefore, 0.80 faradays of electric charge are required to produce 0.80 mol of Na(l) by electrolysis. (Choice B) Using 1.6 faradays of electric charge would produce 1.6 mol Na(l). (Choices C and D) The electrons removed from the Cl⁻ anions in Reaction 1 are the same electrons used to reduce the Na⁺ cations in Reaction 2. Consequently, the ratio of moles of electrons to moles of NaCl is 1:1 rather than 3:1 or 4:1. Educational objective: In an electrolytic cell, electric current from an external source is supplied to provide the necessary energy to perform a nonspontaneous (endergonic), electrochemical decomposition (electrolysis) of a compound. The charge used during electrolysis can be measured in a unit called the faraday, where 1 faraday equals the electric charge present in 1 mole of electrons.

The Overall Reaction for the Electrolysis of Molten Sodium Chloride