Zebra's chem questions....

[Zebra]

1. Does pressure affect the K value? (I always thought temp was the only factor that can change this)
2. Purpose of having a porous electrode ?( This is only in fuel cells right?!?)
3. In a titration against a strong base, it does not matter if the acid is strong or weak.... (what about in a weak base?) .... Can someone clarift the two concepts that I'm confused with ?(ionisation and neutralisation)
4. Sometimes questions have 2 sig.fig data (time or temp) but the answer given is 3 sig.fig even though we made use of these datas. Why's this the case?
5. When something is corrosive, do we ALWAYS use

O2    +     2 H20  + 4 e-   <->   4 OH-?
WHY CAN'T IT BE OTHER HALF REACTIONS INVOLVING WATER??
6.Why do we need to seperate the products of electrolysis ? (e.g KOH, NaCl) is this because the products will react and form the initial reactants giving off heat?

thanks!

[Mao]

1. No, not at normal pressures.

2. Usually only in fuel cells. Two reasons: a) the electrode (Pt) is a catalyst, so you want to maximize surface area to get the most out of your catalyst. b) The products of the half reaction must be able to go through the electrode into the electrolytes, so the electrode must be porous to let the chemicals flow through.

3. acid and base will generally always neutralize each other, no matter the strength. Ionization typically deal with reaction with water, which depends on Ka.

4. They made a mistake.

5. In corrosion, we are always oxidizing the metal. That half reaction has the highest oxidizing potential amongst oxidation reactions containing water.

6. Yes. The products should be separated. However, since the products are generated at separate electrodes, it is fairly easy to keep them separate (as the electrodes are physically placed apart from each other, we can simply funnel the products into different containers)

[Zebra]

1. No, not at normal pressures.

2. Usually only in fuel cells. Two reasons: a) the electrode (Pt) is a catalyst, so you want to maximize surface area to get the most out of your catalyst. b) The products of the half reaction must be able to go through the electrode into the electrolytes, so the electrode must be porous to let the chemicals flow through.

3. acid and base will generally always neutralize each other, no matter the strength. Ionization typically deal with reaction with water, which depends on Ka.

4. They made a mistake.

5. In corrosion, we are always oxidizing the metal. That half reaction has the highest oxidizing potential amongst oxidation reactions containing water.

6. Yes. The products should be separated. However, since the products are generated at separate electrodes, it is fairly easy to keep them separate (as the electrodes are physically placed apart from each other, we can simply funnel the products into different containers)

hey thanks so much MAO!!!