A cr3 + (aq) solution is electrolyzed using a current of 7.40

a. what mass of cr (s) is plated out after 1.85 days?

When Cr+3 + 3e - → Cr (s)

So according to the charge formula:

charge Q = I * t

when we have I (the current) = 7.4 a

and t (the time in seconds) = 1.85d * 24h * 60 min*60sec = 159840 sec

by substitution:

Q = 7.4 a * 159840 sec = 1182816 C

now to get the mass we have to use Faraday constant which is:

F = e NA

= 1.602 x 10^-19 * 6.022 x 10^23

= 96485 C mol^-1

when e is the electron charge & NA Avogadro's number for the charge in on mol

and as we can see from the equation Cu3 + reacts with 3 electrons so,

the mass of Cr (s) = Q * (1mole-/F) * (1molCr / 3 mol e-)

= 1182816 * (1/96485) * (1/3)

= 4.1 g