a) How will the concentration of hydrogen ions be affected?
b) How will the pH change?
c) How does dilution affect the pH of a basic solution?Chemistry question please help?
Let's just use your example to figure out the answers to the questions.
If the pH is 4.0 , according the the equation for pH:
(incase you did not know, H3O+ is the same as talking about H+. Your teacher or professor might just use H+ to keep things simplified in class. But they are both the same thing (although H3O+ is a more accurate description of the acidic species). For this disucssion, we'll just use H3O+
pH = - log [H3O+]
we can find the concentration of the acidic species, H3O+.
to find [H3O+] we need the opposite of the log function.
[H3O+] = 10 ^-pH. That is, 10 raised to the power of negative pH.
= 10^-4.0
so [H3O+] = 1 x 10^-4 Molar or 1 x 10^-4 moles in every 1 L of water.
So what happens if we increase the volume? Lets say we double it to 2 L. What will the concentration be if we have 2 L of water instead of 1?
(1 x 10^-4moles) / 2 Liters = 5 x 10^-5. The concentration has decreased. (10^-5 is smaller than 10^-4).
We have less moles of acid per 1 L (although we have more Liters overall).
the new pH then is: - log (5 x 10^-5)
pH = 4.30.
So to answer Parts A %26amp; B:
Increasing the Volume of solution will DECREASE the concentration of Hydrogen (H3O+) ions.
And because of this, the pH INCREASES (or becomes less acidic or you can say just as easily the solution is becoming more basic).
The pH changed from 4 to 4.30. It increased.
PART C. Diluting a basic solution will have the same kind of opposite affect. Increasing the volume, will mean less moles of base per 1 liter of solution, so the concentration of OH- will DECREASE, and subsequently, the pH will slightly DECREASE towards the acidic range
Less OH means more H+, so the pH decreases.
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