pH and Indicators Flashcards
equation for ionic product of water
H2O ⇌ H+ + OH-
or
H20 + H2O ⇌ H3O+ + OH-
definition of Kw
the product of the concentrations of hydrogen ions and hydroxide ions in water in moles per litre
Kw =
[H+] [OH-]
[ ] means
moles per litre
if the temperatures changes will Kw change and why
yes as it is temperature dependent
pure water
number of OH- equals H+ when water disassociates
[H+] =
√Kw
if acid is added to pure water
H+ ions will increase, system alters to oppose this and OH- in turn is also decreased
if base is added to pure water
OH- ions will increase, system alters to oppose this and H+ in turn is also decreased
if acids are bases are added, does Kw change
no, the ionic product is always 1 x 10^14
does the acidity or alkalinity of pure water change with temperature
no, as [H+] = [OH-] at all temperatures, so pure water is neutral at all temperatures
pH definition
minus the log to the base 10 of the hydrogen ion concentration (mol/l)
pH =
-log10 [H+]
pOH =
-log10 [OH-]
is neutral at 7 for all solutions?
only when at 25ºC
3 limitations of the pH scale
does not work at extremely low concentrations
at 25ºC only
goes for 0-14
what do we use to calculate with strong acids
disassociation equation and its molar ratio
4 points for strong acids
mol/l
disassociation equation
molar ratio
pH = -log10 [H+]
5 points for strong base
mol/l disassociation equation molar ratio pOH = -log10 [OH-] pH = 14 - pOH
Ka or Kb
disassociation constant for acid or base
weak acid equation
[H+] = √Ka[HA]
weak base equation
[OH-] = √Kb[BOH]
all weak acids on the course are
monobasic
3 points for weak acids
mol/l
[H+] = √Ka[HA]
pH = -log[H+]
