Chapter 6

Question 1

a buffer contains either:

Answer 1

1. signifcant amounts of a weak acid and its conjugate base

2. significant amounts of weak base nn d its conjugate acid.

Question 2

buffers:

Answer 2

solutions that resist pH change

Question 3

adding a small amount of strong acid to a buffer converts a stoichiometric amount of base to the conjugate acid and ————- the ph of a buffer

Answer 3

decreases

Question 4

adding a small amount of strong base to a buffer converts a stroichiometric amount of the acid to the conjugate base and ————- the pH of the buffer

Answer 4

increases

Question 5

what factors effect the influence the effectiveness of buffer?

Answer 5

1. the relative amounts of the acid and conjugate base

2. The absolute concentrations of the acid and conjugate base

Question 6

when is a buffer most effective?

Answer 6

when the concentrations of acid and conjugate base are equal also when the conentrations of acid and conjugate base are highest

Question 7

the relative concentrations of acid and conjugate base should not differ by more than a factor of —- in order for a buffer to be reasonably effective?

Answer 7

10

Question 8

a buffer will be most effective when the ratio between acid:base is equal to what?

Answer 8

1

Question 9

buffer capacity:

Answer 9

is the amount of acid or base that we can add to a buffer without destroying its effectiveness

Question 10

acid-base titration:

Answer 10

a titrant in a burreete is added slowly to an analyte in a flask until the reaction is complete.

Question 11

equivalence point:

Answer 11

the point in the titration when the number of moles of base is stoichiometrically equal to the number of moles of acid; the titration is complete

Question 12

before the equivaklence point what is true?

Answer 12

prior to the equivalence point the analyte solution of known concentration in the flask is in excess

Question 13

the volume at the equivalence point in an acid-base titration does not depend on whether the acid being tirtrated is a strong acid or a weak acid but on what?

Answer 13

only on the amount of acid present in solution before the titration begins and on the concentration of the added base.

Question 14

at half neutralization pH=what?

Answer 14

pKa

Question 15

indicator:

Answer 15

are weak acids establish equilibrium with the h2o and H30 in the solution, when the indicator turns colour that is the endpoint. if the indicator is precise enough the end point will be very close to the equivalence point

Question 16

when pH is one unit or more below pKa….

Answer 16

idicator is the colour of HIn

Question 17

when pH is one unit or more above pKa

Answer 17

indicator is the colour of IN

Question 18

equilibrium constant is ———– dependent

Answer 18

temperature

Question 19

solubility of a compound:

Answer 19

is the quantity that dissolves in a certain amount of liquid.

Question 20

the lower the pH, the ——– the solubility

Answer 20

higher

Question 21

precipitation:

Answer 21

will occur when the concentrations of the ions exceed the solubility of the ionic compound

Question 22

how is the reaction quotient (Q)different than Ksp?

Answer 22

Ksp is the value of this product at equilibrium only whereas the Q is the value of the product under any conditions.

Question 23

If Q< Ksp

Answer 23

the solution is unstaurated and more of the solid ionic compound can dissolve in the solution

Question 24

if Q=Ksp

Answer 24

the solution is saturated, the solution is holding the equilibrium amount of the dissolved ions and additional solid does not dissolve in the solution

Question 25

If Q>Ksp

Answer 25

the solution is supersaturated. Under most circumstances, the excess solid precipitates out of the solution