Module 3.3 Acids, Bases, and pH Flashcards
What are acids and bases?
Chemical compounds that have specific properties and a certain number of hydrogen ions (H+) when dissolved in water.
Hydrogen atoms have
1 proton and 1 electron
Hydrogen ions have
lost its electron. Has only 1 proton.
Hydrogen ions are
positively charged
How does dissociation happen?
Sometimes one of the polar covalent bonds of water pulls the electrons so far towards the oxygen that the water molecule falls apart or dissociates
The equation for the dissociation of water is:
H2O → OH- + H+
Rarely during dissociation, H+ is
quickly picked up by a passing water molecule to become H3O+ aka a hydronium ion
When a hydronium ion is made, it results in a
a hydroxide ion left (OH-)
What happens during the dissociation of water?
Water dissociates into hydroxide ions (OH-) and hydrogen ions (H+).
What is the chemical equation for the dissociation of water?
H2O → OH- + H+
What is a hydronium ion?
H3O+, formed when H+ is picked up by a passing water molecule.
How often does the hydrogen ion get picked up during dissociation?
1 in 1x10^7 molecules of water in neutral water
What is the official chemical name of H+?
Hydrogen ion.
How is H+ read
H plus
The hydrogen atom has
1 proton and 1 electron
When the electron is lost in the hydrogen ion, the only part of the hydrogen atom left is the
proton
What defines an acid in biological terms?
A molecule that can donate H+.
An acid increases the hydrogen ions in
a solution
An acidic solution is a solution that has a
high concentration of H+ or hydronium ions
What is the difference between strong acids and weak acids?
Strong acids completely dissociate; weak acids do not.
Give examples of strong acids.
- Sulfuric acid
- Hydrochloric acid
- Nitric acid
Give examples of weak acids.
- Carbonic acid
- Citric acid
- Acetic acid
What defines a base?
Atoms or molecules that can accept H+.
What is a characteristic of a basic solution?
Low concentration of H+ or high concentration of OH-.
Bases decrease
H+ concentrations in a solution
Weak bases do not
dissociate completely
Give examples of weak bases.
- Ammonia (NH3)
What defines strong bases?
They dissociate completely and create OH- ions that can pick up hydrogen ions indirectly.
Strong bases dissociate
completely
Give examples of strong bases.
- Sodium hydroxide
- Sodium phosphate
- Sodium carbonate
What are some properties of acids?
- Taste sour
- Are corrosive
- Conduct electricity
Strong acids nearly completely
dissociate
Weak acids do not do what well?
Dissociate
What percentage of weak acids dissociate
usually only 5%
What is the pH scale?
A measure of the acidity or basicity of an aqueous solution.
Hydronium is more common in
acids
The pH scale goes from
1 to 14
pH stands for
The Power of Hydrogen or the Power of Hydronium
Another way to look at pH is as a measure of
the concentration of H+ in an aqueous solution
Neutral substances
are neither acidic nor basic (ex NaCl and distilled water)
What is the neutral pH value?
7.
The numbers on the scale range from 0 to 14 and reflect
the concentration of H+ and OH- in the solution
A fluid is assigned a number according to
the number of H+ ions present in a liter of that fluid
What does a lower pH number indicate?
Higher concentration of H+ ions and the LOWER the OH- concentration.
What does a higher pH number indicate?
Lower concentration of H+ ions and higher concentration of OH- ions.
What is the pH of an acidic solution?
Below 7.
What is the pH of a basic or alkaline solution?
Above 7.
Low pH is
acidic. It has more H+ ions and fewer OH- ions
High pH is
basic and has more OH- ions and fewer H+ ions
The pH scale is a what kind of scale
logarithmic scale
A logarithmic scale is a base
10
A change of one whole pH number represents
a ten-fold (10X) change in the number of H+ ions
What happens to proteins if the pH changes too much?
They can denature or fall apart.
What are buffers?
Substances that resist sudden changes to the original pH of a solution.
Give an example of a buffer in human blood.
Carbonate-bicarbonate buffer.
What is the formula for the carbonate-bicarbonate buffer?
H2CO3 ↔ HCO3- + H+
Normal pH of blood
7.4
What do buffers do when pH becomes too acidic?
Act like a base and accept H+ ions.
What do buffers do when pH becomes too basic?
Act like an acid and accept OH- ions.
STRONG acids and bases can
neutralize each other
What is neutralization?
A reaction where H+ of an acid combines with OH- of a base to form water.
What are salts?
Substances that dissociate into cations and anions in water, neither of which are H+ or OH-.
How are salts formed?
In a neutralization reaction.
Strong acids and strong bases react to form
water and a salt. They make neutral products.
What are electrolytes?
Salts dissolved in water that conduct electricity.
Examples of electrolytes
Na+
Cl-
K+
Ca2+
Mg2+
What are some functions of electrolytes?
- Maintaining salt/water balance
- Maintaining acid/base balance
- Involved with nerve function and parts of bone and teeth
