3.1.12 Acids and bases Flashcards
Bronsted-Lowery Acid:
Dontate protons.
Bronsted-Lowery Base:
Accept protons.
What ion causes a solution to be acidic?
H+ ions or H3O+
What causes a solution to be alkaline?
OH- (hydroxide ion)
EQUATION pH
pH = -log10[H+]
[H+] = hydrogen ion concentration.
Strong acid:
fully dissociates in water
HX -> H+ + X-
Examples of strong acids:
HCl, H2SO4, H3PO4
Examples of weak bases:
CH3COOH, any organic acid.
What is the concentration of hydrogen ions in a monoprotic strong acid?
It will be the same concentration as the acid.
0.1moldm3 HCl the pH will be -log10[0.1] = 1.00
EQUATION: Find [H+] from pH
[H+] = 1 x 10 ^ -pH
EXAMPLE: STRONG ACID calculate the concentration of HCl with pH of 1.35.
[H+] = 1 x 10^-1.35
0.045 moldm-3
What is the relationship between pH and concentration of H+?
lower pH = high concentration of H+
If two solutions have a difference of 1, what is the difference in [H+]?
factor of 10.
Why is pure water neutral?
[H+(aq)] = [OH-(aq)]
EQUATION Kw
Kw= 1 x 10-14 (at 25 * C)
Kw = [H+(aq)]^2
Example 2: Calculate the pH of water at 50ºC given that Kw = 5.476 x 10-14 mol2 dm-6 at 50ºC
[H+(aq) ] = √ Kw = √ 5.476 x 10-14 =2.34 x 10-7 mol dm-3
pH = - log 2.34 x 10-7 = 6.63
It is still neutral though as [H+(aq) ] = [OH-(aq)]
What is the effect of temperature on the pH of pure water?
At different temperatures to 25 * C the pH of pure water changes.
Dissociation of water is endothermic so increasing the temperature = equilibrium would move to the right giving a bigger concentration of H+ ions and lower pH.
How can you calculate pH from Kw?
Kw = 1.00 x 10-14
[H+]^2 = Kw
[H+] =
