acids and bases Flashcards
define an acid
Bronsted Lowry definition of an acid is a species that donates a proton, H+, during an acid-base reaction
common acids
hydrochloric acid HCl
sulfuric acid H2SO4
nitric acid HNO3
phosphoric acid H3PO4
ethanoic acid CH3COOH
carbonic acid H2CO3
ammonium NH4+
acids change indicators?
blue litmus -> red
phenolpthalein -> colourless
methyl orange -> red
general properties of acids
-tend to be corrosive
-taste sour
-react with bases
-have a pH less than 7
-solutions can conduct an electric current
define a base
Bronsted Lowry definition of a base is a species that accepts a proton, H+, during an acid-base reaction
an alkali is a soluble base that dissociates hydroxide ions
bases change indicators?
phenolpthalein -> pink
methyl orange -> yellow
red litmus -> blue
general properties of bases
-have a slippery feel
-taste bitter
-are caustic
-react with acids
-have a pH above 7 (alkalis only)
-solutions can conduct an electric current
define ionisation
the process by which a chemical species gains or loses an electric charge
define dissociation
the process by which a molecule separates into smaller particles
common bases
sodium hydroxide NaOH
ammonia NH3
magnesium hydroxide Mg(OH)2
potassium hydroxide KOH
oxide O2-
calcium hydroxide Ca(OH)2
conjugates
acid and conjugate base = pair
this is where the acid, has donated a proton and thus the conjugate base has hydrogen less eg. H2O -> OH-
base and conjugate acid = pair
this is where the base, has accepted a proton and thus the conjugate acid has more hydrogen eg. H2O -> H3O+
what are amphiprotic species?
amphiprotic species can either donate or accept a proton, H+
these substances have the availability to accept or donate a proton eg. water
ionic equations
these are simplified equations that do NOT include any spectator ions (aqueous ions which do not react and remain dissolved in solution throughout a reaction)
eg. 2K(s) + 2H+(aq) -> 2K+ (aq) +H2 (g)
strength of acids or bases?
related to how willingly it will donate or accept a proton
strong acid?
one that will undergo complete ionisation when added to water, almost all acid molecules in the solution will donate proton to form aqueous H+ ions
three common = sulfuric acid, hydrochloric acid, nitric acid
weak acids?
does not readily give up its H+ ions in a solution
use the double harpoon to show that these reactions do not go to completion
three common = ammonium, ethanoic acid, carbonic acid
strong bases?
readily accept a proton during an acid base reaction, one that completely dissociates to form hydroxide ions, OH-, and a basic equation
eg. NaOH, KOH, Ca(OH)2
weak bases?/
does not readily accept H+ ions
use double harpoon to show reactions do not go to completion
eg. ammonia, sulfate, ethanoate, bicarbonate, fluoride
strength of conjugate pairs?
strong acids have negligible conjugate bases
strong bases have negligible conjugate acids
strength vs concentration
the strength of an acid relates to what proportion of its molecules will donate a proton, H+
whereas an acids concentration depends on how many of those acid molecules were in the solution to begin with
pH scale
the stronger the acid, the lower the pH value
neutral solutions have a pH of 7
the stronger the base, the higher the pH value
formula to find pH
pH = -log[H3O+]
ionic product of water
[H+] x [OH-] = 10-14 M
finding concentration from pH
[H3O+] = 10^-ph
pH of basic solution
pH = 14 + log[OH-]
equation of weak acid’s reaction with water
HA (aq) + H20 (l) <-> H30+ (aq) + A- (aq)
equilibrium constant expression?
[H30+] [A-] // [HA] [H20]
acid dissociation constant?
Ka - this is the equilibrium constant for the dissociation of an acid in aqueous solution. it tells us how far the reaction has proceeded towards completion before equilibrium is established
Ka = [H30+] [A-] // [HA]
Ka - simple formula
Ka = [H+]^2 // [HA]
knowing the concentration of H3O+ is equal to the conc. of H+
acids and conductivity
not all acids of conc 0.1M have the same pH, and do not conduct electricity to the same extent
conductivity of a solution = directly related to the number of ions in a solution
what happens when an acid is diluted?
the concentration of H+ ions decreases and the pH increases towards 7
