Focus 6A
Provide a definition for each using the idea of solubility/dissociation:
Strong electrolytes
Weak electrolytes
Nonelectrolytes
Strong electrolytes - 100% dissociate into ions in water
Weak electrolytes - Partially dissociate into its ions in water
Nonelectrolytes - Insoluble in water
Log and antilog sig fig rules
input: log (# sig figs)
answer: number of sig figs becomes number of decimal places
input: 10^(# decimal places)
answer: # of decimal places becomes number of sig figs
Comparing weak acid and weak base strength: The ______ the Ka/Kb the stronger the acid/base and the ______ the pKa/pKb the stronger the acid/base.
larger; smaller
Anions of weak acids are ______ and cations of weak bases are _____.
basic; ; acidic
When writing net ionic equations, ____ electrolytes and ______ electrolytes are written as whole compounds while _____ electrolytes are shown as broken into ions.
weak and non; strong
The states that are excluded from an equilibrium expression
liquids and solids
Increases
Anions of strong acids are ____ and cations of strong bases are _____.
both neutral!
Define:
Lewis acids
Lewis bases
Lewis acids accept an electron pair
Lewis bases donate an electron pair
The pH of a 0.35M HCl solution.
pH = - log(0.35) = 0.46
Oxyacid strength increases with ______ and ______.
The more oxygens in the molecule; the more electronegative the molecules present.
Hydroxylamine is a weak molecular base with Kb = 6.6×10−9. What is the pH of a 0.0500 M solution of hydroxylamine?
[ OH- ] = sqrt(Kb*[Base-x]) = sqrt((6.6 × 10−9) (0.0500)) = 1.82 × 10−5 ... continue until convergence
pOH = − log (1.82 × 10−5)= 4.74
pH = 14 − 4.74 = 9.26
Explain the way in which you would solve for the pH of a polyprotic acid solution when its two successive Ka values are less than 1000 factors apart.
Write equations
Conduct first ICE table and obtain x
Use the new x as the starting concentration for the new species and H3O+ concentration
Solve for the new x
Use new hydronium concentration to plug in for pH
Define the following species as Lewis acids or Lewis base:
SO2 and NH3
Lewis acid; Lewis base
The Kb expression for the following equation:
C6H5COO−(aq) + H2O(l) ⇀↽ C6H5COOH(aq) + OH−(aq)
general format --> Kb = [BH][-OH]/[B]
specific --> Kb = ([C6H5COOH][-OH])/[C6H5COO-]
Percent ionization:
A 0.28 M solution of a weak acid is 3.5% ionized. What is the pH of the solution?
2.01
Assume that five weak acids, identified only by numbers (1, 2, 3, 4, and 5), have the following ionization constants. The anion of which acid is the strongest base?
Ionization Constant Ka value
1 1.0 × 10−3
2 3.0 × 10−5
3 2.6 × 10−7
4 4.0 × 10−9
5 7.3 × 10−11
5
Show the net ionic equation for the reaction between perchloric acid and rubidium hydroxide (put water in the liquid state).
OH- (aq) + H+ (aq) --> H2O (l)
The hydroxide concentration of a 0.015M HBr solution at 25oC.
[H3O+][-OH] = 1.0E-14
(0.015M)(-OH) = 1.0E-14
[-OH] = 6.67E-13 M
The law that explains why the successive Ka values of polypro tic acids get smaller and smaller.
Coulomb's Law
For a solution labeled 0.10 M H3PO4(aq), which of the following is true?
1. [H2PO−4 ] is greater than 0.10 M.
2. [PO3−] = 0.10 M. 4
3. [H+] = 0.10 M.
4. [H+] is less than 0.10 M.
5. [H+] = 0.30 M.
statement 4 is correct