Chromium metal can be plated out from an acidic solution containi… - Vidyadip

Question

Chromium metal can be plated out from an acidic solution containing $CrO_3$ according to the following equation:
$\text{CrO}_3(\text{aq})+6\text{H}^+(\text{aq})+6\text{e}^-\xrightarrow{ \ \ \ \ \ \ \ \ \ \ \ }\text{Cr(s)}+3\text{H}_2\text{O}$
Calculate:

How many grams of chromium will be plated out by $24,000$ coulombs.
How long will it take to plate out $1.5g$ of chromium by using $12.5A$ current?

$($At. mass of $Cr = 52).$

✓

Answer

$6 \times 96500$ coulomb deposit $Cr = 1 \ mole = 52g$

$\therefore 24000$ coulomb deposit $Cr =\frac{52\times24000}{6\times96500}\text{g}=2.1554\text{g}$

$52g$ of $Cr$ is deposited by electricity $= 6 \times 96500C$

$\therefore 1.5g$ require electricity $= 1.5C = 16071.9C$
$\therefore$ Time for which the current is required to be passed $=\frac{16071.9\text{C}}{12.5\text{A}}=1336\text{s}$

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