Question

Hey please read this if you know the Principle of LeChatelier...

Answer 1

if i put some NaOH solid powder in water, will it make more water? Because according to LeChatelier principle:

H2O <-> H+ + OH-

If i give more OH-, H2O will increase... so is it true or not?

Answer 2

Another way of saying this is:
If i say, I put give OH-, according the principle, H+ will decrease, so when I calculate the pH, will it take account of this?

Answer 3

Um... You are increasing the total volume of the solution, but not really creating more water. You are shifting the equilibrium of hydroxide and hydronium ions (which is what pOH and pH are measuring, logarithmically)

This is a far more likely cause for an increase in water volume, if there's enough carbon dioxide gas in the water:
\[2 NaOH + CO_2 \rightarrow Na_2CO_3 + H_2O \]

Even with that, consider this:
Does adding a concentrated base or acid into water generate heat? Yes, it does. Does raising the temperature of the water shift the balance of the vapor pressure, causing it to evaporate a bit quicker? Yes it does.

What you'll find is the effect of all these factors, and probably much more that I haven't considered, it won't change much at all. It's a negligible factor. How negligible? That's what experimenting is for! (I wasn't able to find any research on the subject)

Put this in perspective, do you know how many hydroxide and hydronium ions are in perfectly neutral (pH = 7) water? It's a very small number ;-)

Kw = [H+][OH-]

Kw has a value of about 10-14 at 25°C.

Answer 4

This is interesting to think about as a mental exercise, but the effects are so negligible. In short: Hmm...

Answer 5

can you answer my second question?