acids and bases Flashcards
define bronsted lowry acid
is a proton donor
define bronsted lowry base
proton acceptor
what is an amphoteric
a compound (usually a metal oxide or hydroxide) that can act as both an acid and a base
what can you say about the equilibrium of acids and bases
-strong acids and strong bases fully ionise in water so they do not have equilibrium
-weak acids and weak bases partially ionise in water so their equilibrium lies to the left so kc values are very small
what the equation for pH
pH=-log10[H+]
whats the quation for [H+]
10^-log
whats the equation for Kw
kw= [H+}^2
if Kw isnt given what value should you assume it to be
1x10^-14
explain why in Kw [H+]=[OH-]
pure water is neutral so the hydrogen ion conc is equal to the hydroxide ion conc (the H+ and OH- are in 1:1)
when breaking water bonds is that an endothermic or exothermic reaction
endothermic therefore Kw is dependent on temperature
(MEXican BEN: Making bonds is EXOthermic and Breaking bonds is ENDothermic)
explain why Kw increases with temperature
-position of equilibrium shifts to the right, the endothermic direction
-to oppose the increase in temperature
what is a monoprotic base
base that can accept one proton e.gNaOH
what is a diprotic base
base that can accept two protons e.g. Ba(OH)2
whats the equation for a weak acid
Ka= [H+] [A-]/[HA]
whats the equation for pKa
pKa= -logKa
whats the equation for Ka from a pKa value
Ka=10-pKa
what is the relationship between the value of pKa and the strength of the acid
-high value of pKa is a weaker acid(low Ka value)
-low value of pKa is a strong acid (high Ka value)
what is a buffer solution
solution that maintains a constant pH despite the addition of acid, base or water
what are the two types of buffers
acidic which have a pH of below 7
basic which have a pH of above 7
what are acidic buffers made out of
-weak acid(HA) and its salts(A-)
whats the template of how to answer buffer ‘expalin’ questions
-write the buffer equilibrium equation
-what does the added chemical react with
-which way does the equilibrium shift
explain what happens when an acidic buffer is added an acid or a base
HA<—>H+ +A-
addition of acid:
added H+ reacts with A-
eqm shifts to left to decrease H+
addition of base:
-added OH- reacts with H+
-eqm shifts to the right to replace H+
