In: Chemistry

# What mass of Cr(s) is plated out after 1.90 days? What amperage is required to plate out 0.250mol Cr from a Cr3+ solution in a period of 8.60h?

A Cr3+(aq) solution is electrolyzed, using a current of 6.10A.

What mass of Cr(s) is plated out after 1.90 days? What amperage is required to plate out 0.250mol Cr from a Cr3+ solution in a period of 8.60h?

## Solutions

##### Expert Solution

(1) $$\mathrm{Cr} 3++3 \mathrm{e}-\mathrm{m} \mathrm{Cr}$$

charge $$=$$ x time in s

$$=6.10 \times 1.90 \times 24 \times 3600=1001376 \mathrm{C}$$

Moles of electrons = charge/Faraday constant

$$=1001376 / 96485=10.3786 \mathrm{mo}\rceil$$

Moles of $$\mathrm{Cr}=1 / 3 \times$$ moles of electrons

$$=1 / 3 \times 10.3786=3.4595 \mathrm{mo} 7$$

Mass of $$\mathrm{Cr}=$$ moles $$\mathrm{x}$$ molar mass of $$\mathrm{Cr}$$

$$=3.4595 \times 51.996$$

$$=180 \mathrm{~g}$$

(2) Moles of electrons $$=3 \mathrm{x}$$ moles of $$\mathrm{Cr}$$

$$=3 \times 0.250=0.750 \mathrm{mo}\rceil$$

charge $$=$$ moles of electrons $$x$$ Faraday constant

$$=0.750 \times 96485=72363.75 \mathrm{C}$$

Current $$=$$ charge/time in $$\mathrm{s}$$

$$=72363.75 /(8.60 \times 3600)$$

$$=2.34 \mathrm{~A}$$