How many grams of chromium metal are plated out when a constant current of 8.00 a is passed through an aqueous solution containing cr3+ ions for 320. minutes?
a) 27.6 g
b) 49.2 g
c) 82.4 g
d) 248 g

A) m = 27.6 g

Explanation:

Faraday's law:

∴ mass of the substance produced at the electrode (g):

∴ Q = I×t

⇒ Q = ( 8.00 A)(320 min)(60s/min) = 153600 A,s = 153600 C

∴ F = 96485.3365 C/molFaraday's constant

∴ z = 3 valence number

∴ M Cr = 51.9961 g/molmolar mass

⇒ m = ((153600 C)/(96485.3365 C/mol))((51.9961 g/mol)/(3))

⇒ m = 27.592 g ≅ 27.6 g

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