Question

Question 6 (1 point) How many seconds are required to produce 2.91 mg of chromium metal from an acidic solution of potassium dichromate, K2Cr2O7, using a current of 0.580 A? (MMchromium = 51.996 g/mol) Express your answer to the nearest second. Your Answer: Your Answer

Answer 1

Q= I * t where I = current , t = time , Q = amount of electric charge.

K2Cr2O7 --------------> Cr which is Cr6+ + 6electrons --------------> Cr (metal)

So, to produce 1 mole of Cr metal, 6 moles of electronic charge is required, which is 6 * 96500 C.

Now, we shall calculate number of moles of Cr:

Number of moles = mass / molar mass = 2.91 * 10 -3 g / 51.996

= 0.05596 * 10 -3 moles.

to produce 1 mole of Cr metal, 6 * 96500 C moles of electronic charge is required

therfore for 0.05596 * 10 -3 moles of Cr metal, charge required = 6 * 96500 * 0.05596 * 10 -3

= 32.40084 C of electronic charge.

Q= I * t

time = Q / I =  32.40084 C / 0.580 A = 55.8635 seconds