Chemical reactions involve interaction of atoms and molecules. A large number of atoms/molecules (approximately 6.023×1023 are present in a few grams of any chemical compound varying with their atomic/molecular masses. To handle such large numbers conveniently, the mole concept was introduced. This concept has implications in diverse areas such as analytical chemistry, biochemistry, electrochemistry, and radiochemistry. The following example illustrates a typical case, involving chemical/electrochemical reaction, which requires a clear under-standing of the mole concept.
A 4.0 M aqueous solution of NaCl is prepared and 500 mL of this solutionn is electrolyzed. This leads to the evolution of chlorine gas at one of the electrodes (atomic mass of Na is 23 and Hg is 200) (1 F = 96500 C).
If the cathode is an Hg electrode, the maximum weight (in g) of amalgam formed from this solution is
(IIT-JEE, 2007)
Chemical reactions involve interaction of atoms and molecules. A large number of atoms/molecules (approximately 6.023×1023 are present in a few grams of any chemical compound varying with their atomic/molecular masses. To handle such large numbers conveniently, the mole concept was introduced. This concept has implications in diverse areas such as analytical chemistry, biochemistry, electrochemistry, and radiochemistry. The following example illustrates a typical case, involving chemical/electrochemical reaction, which requires a clear under-standing of the mole concept.
A 4.0 M aqueous solution of NaCl is prepared and 500 mL of this solutionn is electrolyzed. This leads to the evolution of chlorine gas at one of the electrodes (atomic mass of Na is 23 and Hg is 200) (1 F = 96500 C).
If the cathode is an Hg electrode, the maximum weight (in g) of amalgam formed from this solution is
(IIT-JEE, 2007)
The correct option is D (d) 446
This is a direct applicaiton of Faraday's law right?
Now here is the catch, you need to know what an amalgum is!
You have studied this and these are basically mixtures that contain mercury. We are going to assume that there is a 1:1 ratio of sodum to mercury in the amalgum and hence you get this:
Na + Hg → Na - Hg
(2 mol) (2 mol)
From here on it is easy to calculate the mass of the amalgum. Remember, the amalgum containds sodium as well as mercury. Hence, the following calculation makes sense.
2 mol of amalgam = 23 × 2 + 2 × 200 = 446 g
This is a direct applicaiton of Faraday's law right?
Now here is the catch, you need to know what an amalgum is!
You have studied this and these are basically mixtures that contain mercury. We are going to assume that there is a 1:1 ratio of sodum to mercury in the amalgum and hence you get this:
Na + Hg → Na - Hg
(2 mol) (2 mol)
From here on it is easy to calculate the mass of the amalgum. Remember, the amalgum containds sodium as well as mercury. Hence, the following calculation makes sense.
2 mol of amalgam = 23 × 2 + 2 × 200 = 446 g
