Question

Gold is plated from a solution of Au³⁺ using a constant current of 4.86 A for 352 minutes.Calculate the grams of gold plated out of solution.

Answer 1

Solution

Given data

Current (I) = 4.86 A

Time = 352 min * 60 sec / 1 min = 21120 second

Gram of the Gold plated out = ?

Reaction is as follows

Au³⁺ +3e-   ---- > Au(s)

Lets first calculate the charge in coulomb (C)

Formula to calculate the charge is

Charge in coulomb = current in ampere * time in second

Now lets put the values in the formula

Charge in coulomb = 4.86 A * 21120 sec

                                   = 102643.2 C

Now lets calculate moles of Au plated

1 mole Au3+ = 3 mole electron

And 1 mole electron = 96485 C

So the moles of electrons = 102643.2 C * 1 mol e- / 96485 C

                                               = 1.0638 mol e-

Now lets calculate the moles of Au plated out

(1.0638 mol e- * 1 mol Au )/ 3 mol e- = 0.3546 mol Au

Now lets convert moles of Au to its mass

Mass of Au = moles * molar mass of Au

Mass of Au = 0.3546 mol * 196.97 g per mol

                    = 69.8 g Au

So the mass of gold plated out = 69.8 g