some questions... plz help

[Zebra]

1.when we add an inert gas to an equilibrium system, the textbook + lisachem says the equilibrium constant does not change. How is this the case? (Is this because it only brings change in the pressure of the system not temperature?). Would an addition of an inert gas affect the reaction rate?

2. Salt-bridge is used to balance charges in each of the half-cells. I don't understand this because in both redox reactions seem to be charge balanced. So..

X => X^+2  + 2e-            (here in oxidation rexn, isn't the charge already balanced?)

3. If the electrolyte in a fuel cell isn't potassium hydroxide, how can this cell be alkaline?

4. What's the difference between a dynamic equilibrium and just equilibrium?

thanks!

[Zebra]

bummmmmmmmmp

[illuminati]

1. Equilibrium constant only changes with changes in temperature. Adding an inert gas will only change the pressure of the system. The addition of an inert gas will not affect the reaction rate, since even though there is an increase in pressure, the relative concentrations of the reactants stays the same.
2. In a galvanic cell, with say X/X^+2 half cell and Zn2+/Zn, where X^+2 is reduced to X, you begin to accumulate Zn2+ in one half cell and negative anions in the other. This effect is called polarisation and the redox reaction is interfered by this build-up of charge in each cell. Hence, a salt bridge such as KNO3 is used not only to complete the circuit, but to allow K+ ions to move to the cathode to balance the negative anion build up, and nitrate ions move to the anode to balance out the Zn2+
3. Doesn't have to be potassium hydroxide, just has to contain hydroxide ions
4. Not too sure. Dynamic equilibrium i believe is when a system is at equilibrium but the forward and back reaction are still occurring; just at the same rate so nothing ACTUALLY happens. Equilibrium could just mean no reaction will occur, but when exams refer to equilibrium its usually just dynamic equilibrium

[Zebra]

'since even though there is an increase in pressure, the relative concentrations of the reactants stays the same'

is this true in a give volume???

[Zebra]

and i dont get how a charge can accumulate. if we look at the oxidation reaction.. clearly the electrons and the cations are balanced! (the charge)

[HenryP]

'since even though there is an increase in pressure, the relative concentrations of the reactants stays the same'

is this true in a give volume???

This only happens in a given volume. If its the pressure that it kept constant and inert gas is added, the volume will be increased and thus the concentrations of the contents will also decrease which may affect the equilibrium.

and i dont get how a charge can accumulate. if we look at the oxidation reaction.. clearly the electrons and the cations are balanced! (the charge)

Well if you think of the galvanic cell, in the anodic half cell electrons are sent through the wire and cations are formed as they lose electrons and thus become more and more positive.
When the cathodic half cell accepts the electrons, they will get more and more negative as more electrons are being accepted.
The salt bridge is used to prevent this, as mentioned above, polarisation. It gives it negative anions to he anodic half cell to balance out the positive charges and the positive cations to the cathodic half cell to balance out the polarisation caused by electrons.
Hope that makes it clearer for you.

[Zebra]

okay thanks guys. so I won't be selling myself short if I just remember that addition of an inert gas DOES NOT AFFECT THE K VALUE ? (haha... i still don't see how this is true but i will take it...)