acids and bases part II
NaCH3CO2 is added to water. what is the pH
CH3CO2- + H20 <---> HCH3CO2 + OH- pH rises above 7 as the concentration of OH- increases (reaction shifts towards weak conjugate acid formed)
net ionic equation for a strong acid-strong base reaction
H+ + OH- ---> H2O
volumes of 1.0 M H3PO4 and 2.0 M NaOH are mixed. Write the net ionic equation for the reaction and identify the aqueous species that have the highest concentrations at equilibrium.
H3PO4 + OH- ---> HPO4^2- + 2 H2O Na+ and HPO4^2- have the highest concentrations because the reaction shifts to the left towards the weak conjugate base producing more products.
Equal volumes of 1.0 M HNO2 and 1.0 M KOH are mixed. Write the net ionic equation for the reaction and identify the aqueous species that have the highest concentrations at equilibrium.
HNO2 + KOH ---> KNO2 + H2O Net: HNO2 + OH- -----> NO2- + H2O K+ and NO2- have the greatest concentrations at equilibrium because this reaction favors the weak conjugate base producing more of the dissociated K+ ions and NO2- ions.
solid potassium oxide is dropped in water
KOH(s) ---> K+ + OH-
if a strong acid or base is involved in a reaction what do we know?
Keq>1 the reaction goes into completion (dissociates completely into ions)
Equal volumes of 2.0 M NH3 and 2.0 M HI are mixed. Write the net ionic equation for the reaction and identify the aqueous species that have the highest concentrations at equilibrium.
NH3 + HI ---> NH4+ + H2O I- and NH4+ have the highest concentrations because the reaction shifted to the right towards the weak conjugate acid producing more products at equilibrium
some anions make solutions basic
anions that are conjugate bases of weak acids accept protons from water to produce OH- these conjugate bases of strong acids will not raise the pH of the solution
how to find the concentration of the excess reactant in a strong acid-strong base reaction
convert the amount of strong acid to moles of H+ with the given volume and concentration of strong acid convert the amount of strong base to moles of OH- with the given volume and concentration of strong base subtract out the smaller amount of moles from the larger amount and whatever is left over is the excess of that reactant then add the two volumes together of both the strong acid and the strong base (make sure it is in liters) then divide the excess reactant over the additive volume in liters to get the concentration of that reactant if the question asks to find the pH of the final solution take the excess of the reactant make sure that if it is OH- in excess that you find the pOH and then find the pH but if it is H+ left in excess then take the negative log to find the pH
metal oxides
metal oxides are basic they can form solid hydorxide
reactions between acids and bases are known as what?
neutralization reactions
salt with weak acids and weak bases
some salts have an acidic cation and a basic anion solutions containing these salts tend to have little or no affect on the pH WEAK-WEAK = LITTLE CHANGE IN PH
weak acid-strong base reactions
strong bases completely dissociate in solution each OH- takes an H+ ion from the weak acid molecule producing water and the conjugate base of the weak acid
what is true about strong acid-strong base reactions
they experience 100% dissociation the H+ and OH- ions combine to form H2O the Keq for this reaction is 1.0x10^14 at 25 degrees C the other parts of these acids and bases act as spectators the pH can be determined from the EXCESS reactant
strong acid-weak base reactions
weak bases will accept protons from a strong acid weak bases may be nitrogen containing compounds such as NH3 or the conjugate bases of weak acids.
