ion with charge 3⁺, like Cr³⁺ needs 3 Faradays to plate 1 mole
Amount of electric charge per mole (faraday's constant) = 96500 C mol¹⁻
Time = 40min = 2400 sec
you have coulombs = amps x sec = 8 x 2400 coulombs
molar mass of Cr = 51.9961g
96500 x 3 coulombs plates 51.9961g Cr
so 8 x 2400 coulombs gives,
51.9961/(96500 x 3) x 8 x 2400 g Cr = 3.45g Cr
so, 3.45g chromium metal is plated out.
The grams of chromium metal plated out is : 3.45 grams
Given data :
Current = 8.00 Amps
Aqueous solution containing Cr³⁺
Time = 40 minutes
molar mass of Cr = 51.9961 g
Cr³⁺ ions requires 3 faradays to be able to plate 1 mole where 1 faraday = 96500 C mol¹⁻
Therefore The time required to plate out Cr³⁺ ions = 3 * 40 minutes = 2400 secs
Next step : convert secs to coulombs
coulombs = current * time
= 8 * 2400 coulombs
Final step : Determine the amount chromium metal plated out
= molar mass / ( faraday constant * 3 ) * 8 * 2400 coulombs
= 51.9961 / ( 96500 * 3 ) * 8 * 2400
= 3.45 grams
Hence we can conclude that 3.45 grams of chromium metal are plated out.
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