Exam 2 Activity of Water

Question 1

Keq formula

Answer 1

Keq = ([C][D]) / ([A][B])

Question 2

pH formula

Answer 2

pH = -log[H+]

Question 3

Freezing point depression formula

Answer 3

deltaTf = Kf*m

Question 4

Universal gas law

Answer 4

PV = nRT

Question 5

T or F: The formula expression are applicable only where ideal behavior is implied i.e. intermolecular, interatomic and/or interionic forces may not be ignored

Answer 5

False; they can be ignored

Question 6

T or F: Interionic attractive forces between oppositely charged ions of strong electrolytes in solution interfere with movement of these ions

Answer 6

True

Question 7

T or F: A strong electrolyte may be completely ionized in solution, yet it is incompletely dissociated into free ions

Answer 7

True

Question 8

T or F: There is interference in the freedom of each of the ions to act towards influencing the freezing point of the solution

Answer 8

True

Question 9

The ______ of the different ions in solution with each other (or even molecules of the same substance as in the case of solutions of nonelectrolytes) results in a _____ between the experimental value of a certain physical or chemical property and the value calculate using stoichiometric concentration in the mathematical expression

Answer 9

Interference; deviation

Question 10

It is better to think of the solution as having an effective concentration that is called ______

Answer 10

Activity

Question 11

Activity, in general, is ___ (more/less) than the actual or stoichiometric concentration of the solute

Answer 11

Less

Question 12

Chemical or physical property =

Answer 12

f (activity)

Question 13

An electrode of a pH meter during a pH measurement responds to the _____ of H+, not its concentration

Answer 13

activity

Question 14

T or F: Since an electrode of a pH meter during a pH measurement responds to the activity of H+, therefore pH = -log(activity H+)

Answer 14

True

Question 15

Ideal gas law looks at ____ vs. pressure

Answer 15

Fugacity

Question 16

Activity measures the _____ ______ of a chemical species whether in the state of gas, liquid, or solid, or whether present as a single species or in combination with other species

Answer 16

Net effectiveness

Question 17

T or F: Activity may be viewed as corrected concentration

Answer 17

True

Question 18

T or F: Activity takes into account the stoichiometric concentration (or pressure in case of gases) as well as any intramolecular attractions, repulsions, or interactions between solute and solvent in solution, association, and ionization

Answer 18

False; …. as well as any intermolecular (not intramolecular)

Question 19

T or F: The activities normally used are relative activites

Answer 19

True

Question 20

T or F: It is possible to assign an absolute value to the activity of a component in solution. Therefore, in order to make quantitative comparisons, a standard state is chosen

Answer 20

True

Question 21

The ____ state of a component in a solution is the state of the component at unit activity

Answer 21

standard state

Question 22

The ____ activity of a component is the _____ of activity in an observed state relative to its value in the standard state

Answer 22

relative activity; ratio of activity

Question 23

T or F: Activity is dimensionless

Answer 23

True

Question 24

Standard state of a solvent is the pure liquid at ___ atmosphere and at a definite temperature. Therefore, for the pure liquid, a = ___

Answer 24

1; 1

Question 25

T or F: If the liquid solute isn't miscible with the solvent, the standard state is the pure solute

Answer 25

False; if the liquid solute is miscible with the solvent

Question 26

T or F: If a solute has a limited solubility, the standard state is a hypothetical solution of unit concentration under conditions of ideal behavior (the solution has characteristics of an infinitely dilute solution)

Answer 26

True

Question 27

Activity is a measure of the _____ tendency of a component in the system, which vapor pressure is a component of

Answer 27

Escaping tendency

Question 28

T or F: Escaping tendency (vapor pressure) is much lower in alcohol vs. water

Answer 28

False; escaping tendency is much lower in water

Question 29

The separation of one component of a solution from another component by means of pressure exerted on a semipermeable membrane

Answer 29

Reverse osmosis

Question 30

Most units of reverse osmosis use a _____ _____ membrane which preferentially permits water to pass through over ions and dissolved matter

Answer 30

cellulose acetate

Question 31

The pores in RO membranes are 5-20 Angstrom units in diameter, which is __-__ cm, and therefore molecules larger than the pores (i.e. with a molecular weight greater than ___) are separated by a simple sieve process

Answer 31

5x10^-8 to 2.5x10^-7 | MW > 200

Question 32

Rejection of salts is as high as ___%, while rejection of most organics is ___%, thus water of extremely high quality can be produced

Answer 32

98%; 100%

Question 33

T or F: In osmosis, water will flow because of potential energy differences from the less concentrated to the more concentrated solution until the system is in equilibrium

Answer 33

True

Question 34

T or F: The addition of pressure to the concentrated solution will stop the transport of water across the membrane when the applied pressure equals the apparent osmotic pressure between the two solutions

Answer 34

True

Question 35

T or F: Apparent osmotic pressure is the difference in the absolute osmotic pressure of each solution. Such a difference is a measurement of the potential energy difference between the two solutions

Answer 35

True

Question 36

T or F: The absolute osmotic pressure is the potential energy difference between any solution and water

Answer 36

True

Question 37

T or F: As more pressure is released from the more concentrated side, the water begins to flow from the more concentrated side to the less concentrated side

Answer 37

False; as more pressure is applied to the more concentrated side

Question 38

At a _____ (static/infinite) dilution, the solute species are separated from each other so far that they do not interact

Answer 38

Infinite

Question 39

The solution behaves ___ and under these conditions, activity = _____

Answer 39

ideally; activity = concentration

Question 40

T or F: As the concentration of the solution is increased, the activity/concentration ratio is increased

Answer 40

False: the ratio is decreased

Question 41

Formula for effective concentration or activity

Answer 41

a = y*m

Question 42

In the formula a = y*m, y is a correction factor called the

Answer 42

Activity coefficient

Question 43

The activity coefficient (y) = 1 in ____ solutions, and therefore, activity = concentration

Answer 43

ideal solutions

Question 44

Which correction coefficient (y) is used for strong electrolytes, and what is the formula?

Answer 44

Strong electrolytes use the correction coefficient of mean ionic activity where (y+/-) = (y+ y-)^0.5

Question 45

Which correction coefficient is used for ions?

Answer 45

Ionic activity coefficient (yi)

Question 46

The mean ionic activity coefficients of all electrolytes is 1 at ___ dilution

Answer 46

Infinite dilution

Question 47

T or F: Mean ionic activity coefficients are expected to equal one at infinite dilution because the solution behaves ideally and (y+/-) is equal to one in the case of ideal solutions

Answer 47

True

Question 48

Log formula for yi

Answer 48

Look up in notes

Question 49

Log formula for y+/-

Answer 49

Look up in notes

Question 50

____ strength is the measure of the intensity of the electrostatic field in a solution due to the presence of ions, and provides a basis for evaluating electrostatic interactions between ions

Answer 50

Ionic strength

Question 51

T or F: Salts that do not have a common ion with a slightly soluble salt can influence its solubility

Answer 51

True

Question 52

What are four areas that ionic strength are important in?

Answer 52

Rates of ionic reactions Solubility of sparingly soluble salts Effects of salts on pH of buffers Biological research