Acid-base Chemistry and Buffering Systems

Question 1

What is a buffer?

Answer 1

A solution composed of a weak acid and its conjugate base that resists change in pH.

Question 2

The degree to which a particular weak acid/conjugate base pair will constrain pH near a given value will depend on the __________.

Answer 2

dissociation tendency of the acid

Question 3

The optimal buffering occurs at a pH equal to its natural _____.

Answer 3

pka

Question 4

The degree to which a buffer solution will continue to resist change with ongoing addition of acid or base is also determined by the ______.

Answer 4

the total concentrations of buffering agents present

Question 5

The total buffering capacity of a weak acid as a function of pH is determined by its ______ and _______.

Answer 5

pka; concentration of buffering species present

Question 6

What is the relationship that describes how experimental buffers are established?

Answer 6

Henderson-Hasselback equation

Question 7

What is the Henderson-Hasselback equation?

Answer 7

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

Question 8

An aqueous solution with a pH of 5 has an abundance of free H3O+ that is _____ times that of a solution with a pH of 6.

Answer 8

10

Question 9

Lower pH means solution is ____.

Answer 9

Stronger acid

Question 10

Higher pH means solution is

Answer 10

Stronger base

Question 11

A solution with a high number of hydrogen ions is ____ and has a ___ pH value

Answer 11

acidic; low

Question 12

A solution with a high number of hydroxide ions is ____ and has a ___ pH value

Answer 12

basic; high

Question 13

The pH scale ranges from ___ to ___

Answer 13

0; 14

Question 14

pH of 7 is ____

Answer 14

neutral

Question 15

What term means that a substance, like water, can act as either an acid or a base?

Answer 15

amphoteric

Question 16

An acid is a proton ___ and a base is a proton _____.

Answer 16

donor; acceptor

Question 17

A buffer is made of a ____ acid and its ____ base.

Answer 17

weak; conjugate

Question 18

Name three examples of weak acid.

Answer 18

HF, HNO2, H2SO3, H3PO4

Question 19

Name 3 examples of strong acids.

Answer 19

HCl, HNO3, HI, HClO4, HClO3, HBr

Question 20

_________ dissociate completely into their ions in water, yielding one or more protons per molecule.

Answer 20

Strong acids

Question 21

The conjugate base is simply the ______ form of the intact acid.

Answer 21

deprotonated

Question 22

What is the medium of life?

Answer 22

water

Question 23

Is water a base or acid?

Answer 23

It can be either

Question 24

What is K_a?

Answer 24

Acid dissociation constant; equilibrium constant

Question 25

The greater the tendency to dissociate, the _____ the acid, the higher the _____

Answer 25

stronger; pKa

Question 26

Weak acids exhibit K_a that is ____ 1

Answer 26

Less than

Question 27

What is the relationship between pka and Ka

Answer 27

pKa = -log(Ka)

Question 28

The optimal buffering capacity of a weak acid will be obtained when the pH of a system is ___ to the pKa of the acid

Answer 28

=

Question 29

When setting up a buffer for an experiment, a ____ acid with a pKa near the target should be used.

Answer 29

weak

Question 30

What were the two types of buffering systems prepared in the Acid-Base Chemistry and Buffering Systems Lab?

Answer 30

1. Tris buffer; and

2. Phosphate buffer

Question 31

______ is a triprotic, capable of donating up to 3 protons.

Answer 31

Phosphoric Acid