MIDTERM - Acids, Bases, pH, and Equilibria in Acid-Base Solutions

Question 1

stands for power/potential of hydrogen

quantitative measure of the acidity and alkalinity of liquid solutions.

It is measured on a scale of 0 to 14.

Answer 1

pH

Question 2

Low pH corresponds to ____ concentrations of 𝑯+ and high pH values correspond to ___ concentration of 𝑯+.

Answer 2

high
low

Question 3

It is also directly related to the ratio of 𝑯+ and 𝑶𝑯− in solutions.

Answer 3

pH

Question 4

increasing acidity

Answer 4

pH<7

Question 5

increasing basicity

Answer 5

pH>7

Question 6

acidity is inversely related to ____

the higher the H+ ion concentration, the ___ the pH

Answer 6

pH

lower

Question 7

The pH of the human body ranges between ____ to ____, with the average at 7.40, in the absence of pathological
states.

Answer 7

7.35 - 7.45

Question 8

caused by an overproduction
of acid that builds up in the blood or
excessive loss of bicarbonate from the
blood (metabolic acidosis) or by a buildup
of carbon dioxide in the blood the results
from poor lung function or depressed
breathing (respiratory acidosis).

Answer 8

Acidosis

Question 9

condition in which the
body fluids have excess base (alkali).
This is opposite of excess acid
(acidosis).

Decreased carbon dioxide
(an acid) level) or increased
bicarbonate (a base) makes the body
too alkaline.

Answer 9

Alkalosis

Question 10

an increase in the hydrogen ion concentration of the blood, resulting in a decrease in pH.

Answer 10

Acidemia

Question 11

a decrease in the hydrogen ion concentration in the blood, resulting in an increase in pH.

Answer 11

Alkalemia

Question 12

The pH level can be measured by using:

Answer 12

a. pH strips/paper
b. pH indicators
c. pH meter

Question 13

2 Methods of pH Determination:

Answer 13

a. Electrometric Method
b. Colorimetric method

Question 14

based on the property of acid-base indicator dyes, which produce color depending on the pH of the sample.

The color change can be measured as an absorbance change spectrophotometrically.

Answer 14

Colorimetric Method

Question 15

a chemical added in a small amount to a solution that causes a color change depending on the pH.

An indicator doesn’t shift color at a precise pH or hydrogen ion concentration. Instead, the color change occurs over a range of hydrogen ion concentration.

Answer 15

pH indicator or acid-base indicator

Question 16

Titrate a WEAK ACID using an indicator that changes under SLIGHTLY ALKALINE solutions.

Answer 16

Titrate a WEAK BASE using an indicator that changes color at a SLIGHTLY ACIDIC pH.

When titrating strong acids or bases, aim for a pH indicator that displays color change near a neutral pH.

Question 17

method used to determine the pH level of a sample using ion-sensitive electrodes.

Answer 17

Electrometric Method

Question 18

a laboratory equipment being used to measure the acidity or alkalinity of a solution. It measures the concentration of hydrogen ions using an ion sensitive electrodes.

It is the most reliable and convenient method for measuring pH.

Answer 18

pH meter

Question 19

a species that produces 𝑯+ ions in water
solution.

Answer 19

Arrhenius acid

Question 20

a species that produces 𝑶𝑯− ions in water
solution.

Answer 20

Arrhenius base

Question 21

a species that accepts an electron pair.

Answer 21

lewis acid

Question 22

species that donates an electron pair.

Answer 22

lewis base

Question 23

proton (𝑯+𝒊𝒐𝒏) donor

Answer 23

bronsted-lowry acid

Question 24

a proton (𝑯+𝒊𝒐𝒏) acceptor

Answer 24

bronsted-lowry base

Question 25

The species formed when a proton is removed from an acid is referred to as the __________ of that acid.

Answer 25

conjugate base

Question 26

The species formed when a proton is added to a base is called the ________ of that base.

Answer 26

conjugate acid

Question 27

LEWIS: acid = base =

Answer 27

electron-pair acceptor electron-pair donor

Question 28

BRONSTED-LOWRY acid = base =

Answer 28

H+ donor H+ acceptor

Question 29

ARRHENIUS acid = base =

Answer 29

H+ donor OH- donor

Question 30

Strong and weak acids differ in the extent of their ______ in water.

Answer 30

ionization

Question 31

Strong acids ionize _______, forming 𝑯+ ions and anions.

Answer 31

completely

Question 32

Weak acids are _____ ionized to 𝑯+ ions in water.

Answer 32

partially

Question 33

The acidic and basic properties of aqueous solutions are dependent on the

Answer 33

equilibrium that involves the water, solvent.

Question 34

pH increases by 1 unit when the concentration of 𝐻+ decreases by a power of 10!

Question 35

WEAK ACIDS (BRONSTED-LOWRY REACTION) Most weak acids fall into one of two categories:

Answer 35

1. Molecules containing an ionizable H atom. 2. Cations.

Question 36

Thousands of molecular weak acids (most of them are organic in nature). Among the molecular inorganic weak acids is nitrous acid:

Answer 36

1. Molecules containing an ionizable H atom

Question 37

The ammonium ion behaves as a weak acid in water; a 0.10 M solution of 𝑁𝐻4𝐶𝑙 has a pH of about 5. The process by which the 𝑁𝐻4+ ion lowers the pH of water can be represented by the equation:

Answer 37

2. Cations

Question 38

Many metal cations act as weak acids in water solutions.

Question 39

The weaker the acid, the smaller the value of 𝐾𝑎.

Answer 39

The weaker the acid, the higher the value of 𝑝𝐾𝑎.

Question 40

The 𝑝𝐾𝑎 value is used to indicate the

Answer 40

strength of an acid.

Question 41

depends on the concentration of weak acid, increasing as the acid is diluted

Answer 41

Percent Ionization

Question 42

[𝐻+]

Answer 42

concentration ionized or equilibrium concentration of hydrogen ion

Question 43

[𝐻A]

Answer 43

original concentration or concentration of weak acid

Question 44

Certain weak acids are _________ they contain more than one ionizable hydrogen atom. The acid equilibrium constant becomes smaller with each successive step.

Answer 44

polyprotic

Question 45

WEAK BASES (Bronsted-Lowry Reaction) Most weak bases fall into one of two categories:

Answer 45

1. Molecules (most are organic compounds, amines). 2. Anions (An anion derived from a weak acid is itself a weak base.)

Question 46

Kb =

Answer 46

base equilibrium constant

Question 47

[𝐵−] =

Answer 47

molar concentration of weak base

Question 48

[𝐻𝐵] =

Answer 48

molar concentration of conjugate acid

Question 49

The weaker the base, the smaller the value of 𝐾b

Answer 49

The weaker the base, the higher the value of 𝑝𝐾𝑏.

Question 50

The 𝑝𝐾𝑎 value is used to indicate the

Answer 50

strength of a base.

Question 51

The larger the value of 𝐊𝐚, the _____ the value of 𝐊𝐛 and vice versa.

Answer 51

smaller

Question 52

From the general relation between 𝐾𝑎 of a weak acid and 𝐾𝑏 of its conjugate weak base, these two quantities are _______ related to each other.

Answer 52

inversely

Question 53

Any solution containing appreciable amounts of both a weak acid and its conjugate base is highly resistant to changes in pH brought about by addition of strong acid or strong base. has a pH close to the 𝒑𝑲𝒂 of the weak acid.

Answer 53

BUFFERS

Question 54

Choosing A Buffer System The pH of the buffer depends on two factors:

Answer 54

1. The acid equilibrium constant of the weak acid, 𝑲𝒂. 2. The ratio of the concentrations or amounts of 𝑯𝑨 and 𝑨−

Question 55

Effect of Added 𝑯+or 𝑶𝑯−on Buffer Systems: The pH of a buffer does change slightly on addition of moderate amounts of a strong acid or strong base.

Answer 55

Addition of 𝐻+ ions converts an equal amount of a weak base𝐵− to its conjugate acid HB:

Question 56

By the same token, addition of 𝑂𝐻− ions converts an equal amount of weak acid to its conjugate base 𝐴−

Question 57

A buffer has a limited capacity to react with 𝐻+ or 𝑂𝐻− ions without undergoing a drastic change in pH.

Question 58

the capacity of a buffer to absorb added 𝑂𝐻− or 𝐻+ ions is _______ related to the slope of the curve.

Answer 58

inversely

Question 59

the pH range over which the buffer is effective. It is related to the ratio of concentrations of the weak acid and its conjugate.

Answer 59

buffer range

Question 60

An acid-base indicator is useful in determining the ____________ of an acid-base titration. This is the point in which reaction is complete; equivalent quantities of acid and base have reacted.

Answer 60

equivalence point

Question 61

If the indicator is chosen properly, the point at which it changes color (its end point) CONINCIDES with the equivalence point.

Answer 61

To understand how and why an indicator changes color, we need to understand the equilibrium principle involved.

Question 62

The color that you see when a drop of indicator solution is added in an acid-base titration depends on the

Answer 62

ratio

Question 63

Strong acids ionize completely in water to form _____ ions strong bases dissolve in water to form ____ ions.

Answer 63

H3O+ OH-