Aqueous Ionic Equilibrium

Question 1

What are buffers?

Answer 1

solutions that resist pH change upon addition of strong acid or strong base

Question 2

What do buffers contain?

Answer 2

significant quantities of both a weak acid and its conjugate base or vice versa

Question 3

What is the HH equation?

Answer 3

pH= pKa + log ([A-]/[HA])

Question 4

When [A-] = [HA], is pH < > or = ?

Answer 4

=

Question 5

When [A-] > [HA], is pH < > or = ?

Answer 5

pH is greater than pKa

Question 6

When [A-] < [HA], is pH < > or = ?

Answer 6

pH is less than pKa

Question 7

What is the two part calulation for determing pH change in a buffer after adding a strong acid/base?

Answer 7

calculate the number of moles that react based on limiting reagent and find new amounts of HA and A-

Calculate pH of resultant solution based on new HA and A- amounts

Question 8

When is a buffer most effective?

Answer 8

when [acid] = [base] for a conjugate acid/base pair (pH = pKa)

Question 9

What pH range are buffers considered effective?

Answer 9

pH = pKa ± 1

Question 10

Are buffers with a higher or lower concentration more effeective?

Answer 10

higher concentration means more effective

Question 11

What is the main use of a titration?

Answer 11

determine the concentration of an
acid or base in solution using a solution of acid or base of known concentration

Question 12

At the eqvuivalence point the moles of acid equal what?

Answer 12

moles of the base

Question 13

Does the equivalence point always at pH=7?

Answer 13

no

Question 14

What can the solubility of an ionic salt be represented by?

Answer 14

an equilibirum process

Ksp

Question 15

What is molar solubility? Is it the same as Ksp?

Answer 15

solubility of moles of solute per litre of solution

no its not identical to Ksp

Question 16

How can you calculate molar solubility?

Answer 16

using an ICE table and Ksp

Question 17

How can you predict if something will precipitate?

Answer 17

by comparing Q and Ksp

Question 18

Which situation will cause a precipitate? Q<Ksp, Q>Ksp, Q=Ksp?

Answer 18

Q<Ksp, unsaturated solution (no precipitate)

Q=Ksp, saturated solution ( no precipitate)

Q>Ksp, supersaturated solution (precipitate occurs)

Question 19

How can you caluculate and figure out if something will precipitate?

Answer 19

calculate the ion concentrations after mixing the solutions

make sure dilution (volume) is taking into account

calculate Q for the ions and compare to Ksp