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):

m = Q/F. M/z

∴ Q = I*t

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

∴ F = 96485.3365 C/mol ... Faraday's constant

∴ z = 3 ... valence number

∴ M Cr = 51.9961 g/mol ... molar mass

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

⇒ m = 27.592 g ≅ 27.6 g