Arrhenius theory of acids and bases Flashcards
What happens to hydrogen chloride when it is added to water?
It dissociates into H+ ions and Cl- ions
What are monobasic acids and give examples of such?
Molecules of which dissociate to give one H+ ion in aqueous solution, examples are hydrochloric acid and nitric acid.
What are dibasic acids and give examples of such?
A molecule of which can dissociate to give 2 H+ ions in aqueous solutions, an example is sulfuric acid
What are tribasic acids and give examples of such?
A molecule of which can dissociate to give three H+ ions in aqueous solutions, an example is phosphoric acid
Give one equation for the following:
monobasic, dibasic, tribasic
Monobasic: HCl —> H+ + Cl-
Dibasic: H₂SO₄ —> 2H+ + SO₄2-
Tribasic: H₃PO₄—> 3H+ + PO₄3-
What are the other names for monobasic, dibasic, tribasic?
Monoprotic, diprotic, triprotic
Are hydrochloric acid, sulfuric acid and nitric acid weak or strong acids? Why?
They are all strong acids as they fully dissociate in water (almost every molecule breaks up to give H+)
Define Arrhenius’ definition of an acid
Arrhenius Definition: An acid is a substance that dissociates in water to produced H+ ions
Define Arrhenius’ definition of a strong acid
Arrhenius Definition: a strong acid is a substance that almost completely dissociates in water to give hydrogen ions.
Define Arrhenius’ definition of a weak acid
Arrhenius definition: a weak acid is a substance that only slightly dissociates in water to give hydrogen ions.
Are ethanoic and methanoic (formic) acid weak or strong acids? Why?
They are described as weak acids as they dissociate only to a slight extent in water.
What are H+ (hydrogen atoms that have lost an electron) exactly?
They are simply bare protons
Bare protons cannot exist independently in solution, what happens to the H+ ion in water?
The H+ ion reacts with water molecules to form H₃O⁺ ion.
In the structure of H2O joining with the H+ ions, one of the lone pairs on the oxygen atom forms a covalent bond with the proton. Both electrons in this bond come from the same atom.
describe this bond.
Such a bond is called a dative covalent bond or a coordinate covalent bond.
Dative means giving in Latin since the same atom gives both of the shared pair of electrons in the bond.
What is the H₃O⁺ ion called?
The hydronium ion
What is important to know about the hydronium ion/H₃O⁺?
It is present in every acidic solution
Show the more accurate equation to represent the dissociation of acids in water in the case of HCl
HCl + H2O —> H₃O⁺ + Cl-
What do aqueous solutions of acids actually contain?
Aqueous solutions of acids contain H₃O⁺ ion and not H+ ions
If substances such as pure ethanoic acid or pure hydrogen chloride are added to solvents such as benzene, no H+ or H₃O⁺ ions are found to be present. Why is this?
These acids only show acidic properties when dissolved in water.
What is the OH- ion called?
the hydroxide ion
Define Arrhenius’ definition of a base
Arrhenius definition: A base is a substance that dissociates in water to produce OH- ions.
Define Arrhenius’ definition of a strong base
Arrhenius definition: a strong base is a substance that almost completely dissociates in water to give hydroxide (hydroxyl) ions.
Define Arrhenius’ definition of a weak base
Arrhenius definition: A weak base is a substance that only slightly dissociates in water to give hydroxide ions.
Give examples of weak and strong bases
Weak: calcium hydroxide, magnesium hydroxide
Strong: sodium hydroxide
What is a base that dissolves in water often referred to as?
an alkali
