Case 4: Too much or too little
Learning goals
What is pH? (OH-)
pH is an easy number to determine the H3O+ concentration. pOH is used to determine the
OH- concentration.
Bases, acids, and alkaline (what makes them weak and strong?)
An acid is a substance that produces H3O+ ions in aqueous solution, which has an pH
<7, and a base is a substance that produces OH- ions in aqueous solution, which has
a pH >7.
H+(aq)+ H2O(l) -> H3O+(aq)
H+ + OH− ⇌ H2O
To understand this process, we use the Lewis structure to show the transfer from a
proton from an acid to a base, by using a curved arrow. Then we show the change in
position of electron pairs during the reaction using this curved arrow. The tail of the
curved arrow is located at the electron pair. The head of the curved arrow shows the
new position of the electron pair.
The strength of an acid or a base is not related to its concentration
Conjugate acid–base pair: A pair of molecules or ions that are related to one another
by the gain or loss of a proton
Conjugate base: A substance formed when an acid donates a proton to another
molecule or ion
Conjugate acid: A substance formed when a base accepts a proton
An acid is a proton donor, a base is a proton acceptor, and an acid–base reaction is a
proton-transfer reaction.
Different types
- Strong acid: An acid that ionizes completely in aqueous solution. So they are
strong because they completely dissociate to give H3O+ ions
- Weak acid: An acid that is only partially ionized in aqueous solution. It is
weak, because it converts a much smaller concentration of H3O+ ions.
, - Strong base: A base that ionizes completely in aqueous solution.
- Weak base: A base that is only partially ionized in aqueous solution
Acids are classified as monoprotic, diprotic, or triprotic depending on the number of
protons each may give up: monoprotic acids, diprotic acids, triprotic acids etc.
The strong acids and bases are strong electrolytes. Almost all other acids and bases
are weak electrolytes. An electrolyte is a substance that conducts an electric current
when dissolved in water or when in the molten state. Because the strong acids and
bases dissolve more, they also conduct more electric current.
Alkaline
An alkali is a basic, ionic salt of an alkali metal or alkaline earth metal chemical
element. An alkali also can be defined as a base that dissolves in water, so a pH > 7.
Alkalis are usually defined as a subset of the bases. One of two subsets is commonly
chosen.
- A basic salt of an alkali metal or alkaline earth metal
- Any base that is soluble in water and forms hydroxide ions or the solution of
a base in water.
Different reactions
- Neutralization: when a strong corrosive acid reacts with a strong corrosive
base, the product has neither acidic nor basic properties. We call such a
solution neutral.
- Reaction with metals: Strong acids react with certain metals to produce
hydrogen gas, H2, and a salt.
- Reaction with metal hydroxides: Acids react with metal hydroxides to give a
salt and water
- Reaction with metal oxide: Strong acids react with metal oxides to give water
and a salt
- Reaction with carbonates and bicarbonates: When a strong acid is added to a
carbonate, bubbles of carbon dioxide gas are rapidly given off. The overall
reaction is a summation of two reactions.
In the first reaction, carbonate ion reacts with H3O+ to give carbonic
acid.
Almost immediately, in the second reaction, carbonic acid
decomposes to carbon dioxide and water.
To generalize, any acid stronger than carbonic acid will react with carbonate
or bicarbonate ion to give CO2 gas
- Reaction with ammonia and amines: Any acid stronger than NH4+ is strong
enough to react with NH3 to form a salt. The base strength of most amines is
similar to that of NH3, which means that amines also react with acids to form
salts.
We can treat the concentration of water, [H2O], as a constant equal to 1000 g/L or
approximately 55.49 mol/L. We can then combine these two constants (K and
Learning goals
What is pH? (OH-)
pH is an easy number to determine the H3O+ concentration. pOH is used to determine the
OH- concentration.
Bases, acids, and alkaline (what makes them weak and strong?)
An acid is a substance that produces H3O+ ions in aqueous solution, which has an pH
<7, and a base is a substance that produces OH- ions in aqueous solution, which has
a pH >7.
H+(aq)+ H2O(l) -> H3O+(aq)
H+ + OH− ⇌ H2O
To understand this process, we use the Lewis structure to show the transfer from a
proton from an acid to a base, by using a curved arrow. Then we show the change in
position of electron pairs during the reaction using this curved arrow. The tail of the
curved arrow is located at the electron pair. The head of the curved arrow shows the
new position of the electron pair.
The strength of an acid or a base is not related to its concentration
Conjugate acid–base pair: A pair of molecules or ions that are related to one another
by the gain or loss of a proton
Conjugate base: A substance formed when an acid donates a proton to another
molecule or ion
Conjugate acid: A substance formed when a base accepts a proton
An acid is a proton donor, a base is a proton acceptor, and an acid–base reaction is a
proton-transfer reaction.
Different types
- Strong acid: An acid that ionizes completely in aqueous solution. So they are
strong because they completely dissociate to give H3O+ ions
- Weak acid: An acid that is only partially ionized in aqueous solution. It is
weak, because it converts a much smaller concentration of H3O+ ions.
, - Strong base: A base that ionizes completely in aqueous solution.
- Weak base: A base that is only partially ionized in aqueous solution
Acids are classified as monoprotic, diprotic, or triprotic depending on the number of
protons each may give up: monoprotic acids, diprotic acids, triprotic acids etc.
The strong acids and bases are strong electrolytes. Almost all other acids and bases
are weak electrolytes. An electrolyte is a substance that conducts an electric current
when dissolved in water or when in the molten state. Because the strong acids and
bases dissolve more, they also conduct more electric current.
Alkaline
An alkali is a basic, ionic salt of an alkali metal or alkaline earth metal chemical
element. An alkali also can be defined as a base that dissolves in water, so a pH > 7.
Alkalis are usually defined as a subset of the bases. One of two subsets is commonly
chosen.
- A basic salt of an alkali metal or alkaline earth metal
- Any base that is soluble in water and forms hydroxide ions or the solution of
a base in water.
Different reactions
- Neutralization: when a strong corrosive acid reacts with a strong corrosive
base, the product has neither acidic nor basic properties. We call such a
solution neutral.
- Reaction with metals: Strong acids react with certain metals to produce
hydrogen gas, H2, and a salt.
- Reaction with metal hydroxides: Acids react with metal hydroxides to give a
salt and water
- Reaction with metal oxide: Strong acids react with metal oxides to give water
and a salt
- Reaction with carbonates and bicarbonates: When a strong acid is added to a
carbonate, bubbles of carbon dioxide gas are rapidly given off. The overall
reaction is a summation of two reactions.
In the first reaction, carbonate ion reacts with H3O+ to give carbonic
acid.
Almost immediately, in the second reaction, carbonic acid
decomposes to carbon dioxide and water.
To generalize, any acid stronger than carbonic acid will react with carbonate
or bicarbonate ion to give CO2 gas
- Reaction with ammonia and amines: Any acid stronger than NH4+ is strong
enough to react with NH3 to form a salt. The base strength of most amines is
similar to that of NH3, which means that amines also react with acids to form
salts.
We can treat the concentration of water, [H2O], as a constant equal to 1000 g/L or
approximately 55.49 mol/L. We can then combine these two constants (K and
