MIDTERM - Acids, Bases, pH, and Equilibria in Acid-Base Solutions Flashcards
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.
pH
Low pH corresponds to ____ concentrations of π―+ and high pH values correspond to ___ concentration of π―+.
high
low
It is also directly related to the ratio of π―+ and πΆπ―β in solutions.
pH
increasing acidity
pH<7
increasing basicity
pH>7
acidity is inversely related to ____
the higher the H+ ion concentration, the ___ the pH
pH
lower
The pH of the human body ranges between ____ to ____, with the average at 7.40, in the absence of pathological
states.
7.35 - 7.45
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).
Acidosis
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.
Alkalosis
an increase in the hydrogen ion concentration of the blood, resulting in a decrease in pH.
Acidemia
a decrease in the hydrogen ion concentration in the blood, resulting in an increase in pH.
Alkalemia
The pH level can be measured by using:
a. pH strips/paper
b. pH indicators
c. pH meter
2 Methods of pH Determination:
a. Electrometric Method
b. Colorimetric method
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.
Colorimetric Method
a chemical added in a small amount to a solution that causes a color change depending on the pH.
An indicator doesnβt shift color at a precise pH or hydrogen ion concentration. Instead, the color change occurs over a range of hydrogen ion concentration.
pH indicator or acid-base indicator
Titrate a WEAK ACID using an indicator that changes under SLIGHTLY ALKALINE solutions.
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.
method used to determine the pH level of a sample using ion-sensitive electrodes.
Electrometric Method
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.
pH meter
a species that produces π―+ ions in water
solution.
Arrhenius acid
a species that produces πΆπ―β ions in water
solution.
Arrhenius base
a species that accepts an electron pair.
lewis acid
species that donates an electron pair.
lewis base
proton (π―+πππ) donor
bronsted-lowry acid
a proton (π―+πππ) acceptor
bronsted-lowry base
The species formed when a proton is removed from an acid is referred to as the __________ of that acid.
conjugate base
The species formed when a proton is added to a base is called the ________ of that base.
conjugate acid
LEWIS:
acid =
base =
electron-pair acceptor
electron-pair donor
BRONSTED-LOWRY
acid =
base =
H+ donor
H+ acceptor
ARRHENIUS
acid =
base =
H+ donor
OH- donor
Strong and weak acids differ in the extent of their ______ in water.
ionization
Strong acids ionize _______, forming π―+ ions and anions.
completely
Weak acids are _____ ionized to π―+ ions in water.
partially
The acidic and basic properties of aqueous solutions are dependent on the
equilibrium that involves the water, solvent.
pH increases by 1 unit when the concentration of π»+ decreases by a power of 10!
WEAK ACIDS (BRONSTED-LOWRY REACTION)
Most weak acids fall into one of two categories:
- Molecules containing an ionizable H atom.
- Cations.
Thousands of molecular weak acids (most of them are organic in nature).
Among the molecular inorganic weak acids is nitrous acid:
- Molecules containing an ionizable H atom
The ammonium ion behaves as a weak acid in water; a 0.10 M solution of ππ»4πΆπ has a pH of about 5.
The process by which the ππ»4+ ion lowers the pH of water can be represented by the equation:
- Cations
Many metal cations act as weak acids in water solutions.
The weaker the acid, the smaller the value of πΎπ.
The weaker the acid, the higher the value of ππΎπ.
The ππΎπ value is used to indicate the
strength of an acid.
depends on the concentration of weak acid, increasing as the acid is diluted
Percent Ionization
[π»+]
concentration ionized or equilibrium concentration of hydrogen ion
[π»A]
original concentration or concentration of weak acid
Certain weak acids are _________
they contain more than one ionizable
hydrogen atom.
The acid equilibrium constant becomes smaller with each successive step.
polyprotic
WEAK BASES (Bronsted-Lowry Reaction)
Most weak bases fall into one of two categories:
- Molecules (most are organic compounds, amines).
- Anions (An anion derived from a weak acid is itself a weak base.)
Kb =
base equilibrium constant
[π΅β] =
molar concentration of weak base
[π»π΅] =
molar concentration of conjugate acid
The weaker the base, the smaller the
value of πΎb
The weaker the base, the higher the value of ππΎπ.
The ππΎπ value is used to indicate the
strength of a base.
The larger the value of ππ, the _____ the value of ππ and vice versa.
smaller
From the general relation between πΎπ of a weak acid and πΎπ of its conjugate weak base, these two quantities are _______ related to each other.
inversely
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 ππ²π of the weak acid.
BUFFERS
Choosing A Buffer System
The pH of the buffer depends on two factors:
- The acid equilibrium constant of the weak acid, π²π.
- The ratio of the concentrations or amounts of π―π¨ and π¨β
Effect of Added π―+or πΆπ―βon Buffer Systems:
The pH of a buffer does change slightly on addition of moderate amounts of a strong acid or strong base.
Addition of π»+ ions converts an equal amount of a weak baseπ΅β to its conjugate acid HB:
By the same token, addition of ππ»β ions converts an equal amount of weak acid to its conjugate base π΄β
A buffer has a limited capacity to react with π»+ or ππ»β ions without undergoing a drastic change in pH.
the capacity of a buffer to absorb added ππ»β or π»+ ions is _______ related to the slope of the curve.
inversely
the pH range over which the buffer is effective.
It is related to the ratio of concentrations of the weak acid and its conjugate.
buffer range
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.
equivalence point
If the indicator is chosen properly, the point at which it changes color (its end point) CONINCIDES with the equivalence point.
To understand how and why an indicator changes color, we need to understand the equilibrium principle involved.
The color that you see when a drop of indicator solution is added in
an acid-base titration depends on the
ratio
Strong acids ionize completely in water to form _____ ions
strong bases dissolve in water to form
____ ions.
H3O+
OH-
