Electrolysis of an alkaline earth metal chloride using a...

Electrolysis of an alkaline earth metal chloride using a current of $5.00 \mathrm{~A}$ for $748 \mathrm{~s}$ deposits $0.471 \mathrm{~g}$ of metal at the cathode. What is the identity of the alkaline earth metal chloride?

Key Concepts

Faraday's Laws of Electrolysis

Faraday's laws establish that the mass of a substance altered at an electrode during electrolysis is directly proportional to the quantity of electric charge passed through the electrolyte. This principle allows one to link the measured charge (obtained from the current and time) with the number of moles of electrons involved in the deposition process, making it fundamental in calculations in electrochemistry.

Charge Calculation from Current and Time

The relationship between electric current, time, and charge is expressed by the equation Q = I × t, where Q is the total electric charge. This calculation is critical because the total charge passed during the electrolysis gives the number of electrons that participate in reducing ions at the cathode, directly influencing the amount of metal deposited.

Electrochemical Reaction Stoichiometry

In an electrochemical deposition process, the stoichiometry of the electrode reaction determines how many electrons are needed to reduce one ion of a metal to its elemental form. For example, when depositing a metal ion with a +2 charge, two electrons are required for the conversion to the neutral metal. This stoichiometric relationship is essential for connecting the total charge passed to the mass of the metal deposited.

Molar Mass Determination and Metal Identification

By calculating the moles of metal deposited from the measured charge and known stoichiometry, and then using the actual mass of deposited metal, one can determine the metal's molar mass. This molar mass is then compared with known atomic masses to identify the metal. This approach is particularly useful for determining the identity of metals in electrolysis experiments.

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