Question

Molar masses can be determined through electroplating. Determine the molar mass and identity of X+3 metal that plates 37.5 g of X in 13.5 hours at a current of 4 A.

Answer 1

Given,

Current = 4 A

Time = 13.5 hours = 13.5 x 3600 = 48600 s

=> Total Charge passed = 48600 x 4 =194400 C

Charge on 1 electron (e-) = 1.602 x 10^-19 C

=> Total number of e- involved = 194400 / 1.602 x 10^-19 = 1.213 x 10^24 e-

=> Moles of e- = 1.213 x 10^24 / 6.022 x 10^23 = 2.015 moles

X3+ + 3e- ----> X

For 1 mole of X, 3 moles of e- is required.

=> Moles of X involved = 2.015 / 3 = 0.672 moles

Mass of X = 37.5 g

Molar Mass = Mass / Moles = 37.5 / 0.672 = 55.8 g / mol