Question

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

Answer 1

A) m = 27.6 g

Step-by-step 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