Corrosion of an iron pipe can be prevented by connecting it to a magnesium bar buried in the ground - VCE - SSCE Chemistry - Question 14 - 2009 - Paper 1

To determine the amount of magnesium corroding, we can use Faraday's laws of electrolysis. The formula relating current (I), charge (Q), and moles (n) is given by:

$Q = n imes F$

Where:

• Q is the total charge (in Coulombs)
• n is the number of moles of substance (magnesium in this case)
• F is Faraday's constant (approximately 96485 C/mol)

The charge can also be calculated from current and time:

$Q = I imes t$

Given that:

• I = 2.0 x 10^-6 A (Amperes),
• t = 1 second,

we can plug the values in:

$Q = 2.0 imes 10^{-6} ext{ A} imes 1 ext{ s} = 2.0 imes 10^{-6} ext{ C}$

Now, substituting Q into the first equation:

$n = \frac{Q}{F} = \frac{2.0 imes 10^{-6}}{96485} \approx 2.07 \times 10^{-11} ext{ mol}$

Thus, the calculated amount of magnesium metal reacting each second is approximately ( 2.1 imes 10^{-11} ext{ mol} ). Therefore, the correct answer is B: 2.1 x 10^-11.