State in words the meaning of the charge balance equation.The force (in newtons) between two charges q1 and q2 (coulombs, C) is given by: `F = (-8.988 *10^9) (q_1 q_2)/(r^2)` where r is the...

State in words the meaning of the charge balance equation.

The force (in newtons) between two charges q1 and q2 (coulombs, C) is given by:

`F = (-8.988 *10^9) (q_1 q_2)/(r^2)`

where r is the distance (in meters) between the two charges.

What is the force (in pounds) between the beakers separated by 1.5 m if one beaker contains 250 ml of solution with 1.0*10^{-06} M excess negative charge and the other has 250 ml of 1.0^{-06} M excess positive charge. There are 9.648*10^{4} coloumbs per mole of charge and 0.224 pounds per newton.

What is the implication of this answer with respect to the need to maintain charge neutrality?

Expert Answers
pnrjulius eNotes educator| Certified Educator

The charge balance equation simply says that if you start with an equal number of positive and negative charges (which most substances have), you will end with an equal number of positive and negative charges. So a solution made up of neutral components must itself be net neutral; any positive ions must be matched exactly with an equal quantity of negative ions.

The force here is just a matter of plugging into the equation, watching our units carefully (especially our molarity M, which is mol/L:

`F = (0.224 {lb}/N) (-8.988*10^{9} N/C^2/m^2) * ((10^{-6} {mol}/L) * (9.648 * 10^{4} C/{mol}) * (0.250 L) * (10^{-6} {mol}/L) *(9.648 *10^{4} C/{mol}) * (0.250 L))/(1.5 m)^2 `
`F = 0.201 * 10^{9} * (2.412*10^{-2})^2 / (1.5)^2 lb`

`F = 5.20 * 10^{4} lb`

This is huge amount of force; the beakers would crash into each other.

What this means for the charge balance equation is that theoretically one could separate the positive and negative ions, but it requires an enormous amount of force, and wouldn't happen on its own. The charge balance equation is what happens if the system is allowed to settle into equilibrium, and in practice it doesn't really take long to settle.