Chemistry, 06.08.2019 06:10 jesusmojica25

How many coulombs are required to plate a layer of chromium metal 0.28 mm thick on an auto bumper with a total area of 0.40 m2 from a solution containing cro2−4? the density of chromium metal is 7.20 g/cm3.

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Answer from: kittybatch345

Explanation:

The given data is as follows.

Thickness = 0.28 mm = $0.28 \times \frac{1}{10}$ cm = 0.028 cm

Area = 0.40 $m^{2}$ = $0.40 \times 10^{4} cm^{2}$ = 4000 $cm^{2}$

As, it is known that volume = area × thickness

So, Volume = $4000 cm^{2} \times 0.028 cm$

= 112 $cm^{3}$

As density is mass divided by volume. So, mass of chromium will be calculated as follows.

Density = $\frac{mass}{volume}$

7.20 $g/cm^{3}$ = $\frac{mass}{112 cm^{3}}$

mass = 806.4 g

As, mass of 1 mole of chromium is 52 g. So, number of moles in 806.4 g of chromium will be as follows.

No. of moles = $\frac{mass}{molar mass}$

= $\frac{806.4 g}{52 g}$

= 15.50 mol

In chromate ion, ( $CrO^{2-}_{4}$ ) charge on Cr is +6. It means that 6 electrons are needed to reduce $Cr^{+6}$ into Cr.

As, 1 mole of $Cr^{+6}$ ions require 6 moles of electrons. Therefore, moles of electrons for 15.50 mol will be calculated as follows.

6 × 15.50 mol = 93.04 mol

To calculate number of electrons we multiply number of moles by Avogadro's number as follows.

$93.04 mol \times 6.02 \times 10^{23}$

= $560.13 \times 10^{23}$

= $5.6 \times 10^{25}$ electrons

There is magnitude of $6.241 \times 10^{18}$ times the charge on an electron is equal to 1 coulomb.

Hence, number of coulombs will be as follows.

No. of coulombs = $\frac{5.6 \times 10^{25}}{6.241 \times 10^{18}}$

= $0.897 \times 10^{7}$ C

or, = $8.97 \times 10^{6}$ C

Thus, we can conclude that $8.97 \times 10^{6}$ C are required to plate a layer of chromium metal with given data.

Answer from: Quest

answer: the rate of diffusion increases with increase in temperature.

increase in temperature, increases the molecular/particles speed (kinetic energy. diffusion means movement of particles through the material.

generally, the heavier the particle the more it interacts with the environment and more the temperature matters. so higher temperature results in higher diffusion.

Answer from: Quest

Yes she is correct. the answer is completely correct

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