Textbook Ch.4: Reactions in Aqueous Solution Flashcards
Molarity
the concentration of a solute in solution
molarity (M) = moles of solute / liters of solution
What does the symbol [ ] represent?
the molarity of a species in solution
What can the molarity of a solution be used to calculate?
- The number of moles of solute in a given volume of solution
- The volume of solution containing a given number of moles of solute
Precipitate
formed when two different ionic compounds are mixed, an insoluble solid separates out of a solution
- The precipitate that forms is itself ionic
- The cation comes from one solution, the anion comes from the other
Net ionic equation
the chemical equation that shows only those elements, compounds, and ions that are directly involved in the chemical reaction.
What does a net ionic equation have to show?
- Atom balance (same number of atoms of each element on both sides)
- Charge balance (must be the same total charge on both sides)
Acid
a species that produces H⁺ ions in water solution
Base
a species that produces OH⁻ ions in a water solution
Strong acids
acids that ionize completely, forming H⁺ ions and anions
Weak acids
acids that only partially ionize to H⁺ ions in water
What does a double arrow ⇌ symbol mean?
the reaction does not go into completion, instead a mixture is formed containing significant amounts of both products and
reactants
Strong bases
bases that completely ionize into OH⁻ ions and cations
Weak bases
produce OH⁻ ions by reacting with water molecules, acquiring H⁺ ions and leaving OH⁻ ions behind
Strong acid-strong base reactions
acids and bases both completely and the H⁺ and OH⁻ ions react with each other to form H₂O molecules, this reaction is referred to as neutralization
What is the net ionic equation for a strong acid-strong base reaction?
H⁺(aq) + OH⁻(aq) —> H₂O
Weak acid-strong base reactions
a two-step reaction occurs
- Ionization of the weak acid into H+ and an anion
- Neutralization of the H+ ions produced from (1) react with the OH- of the base to produce water
What is the net ionic equation for a weak acid-strong base reaction?
HB(aq) + OH⁻(aq) —> H₂O + B⁻(aq)
Strong acid-weak base reactions
two-step reaction occurs
- Acid reacts with water to form cations and OH⁻
- Neutralization occurs when ions produced from (1) react with the OH⁻ of the base to produce water
What is the net ionic reaction for a strong-acid weak base reaction?
H⁺(aq) + B(aq) —> BH⁺(aq)
Titration
when acid-base reactions in water solution are commonly used to determine the concentration of a dissolved species or its
percentage in a solid measure, so the volume of a standard solution (a solution of known concentration) required to react with a measured amount of sample is measured
Redox reaction
a reaction in an aqueous solution that involves a transfer of electrons between two species
Which species in a redox reaction is considered to be oxidized?
the species that loses (i.e. donates) electrons
Which species in a redox reaction is considered to be reduced?
the species that gains (i.e. received) electrons
How are redox reactions split?
it can be split into two half-equations, one of oxidation and the other of reduction
What is unique to redox reactions?
- Oxidation and reduction occur together in the same reaction; you can’t have one without the other
- there is no net charge in the number of electrons in a redox reaction. Those given off in the oxidation half-reaction are taken
on by another species in the reduction half-reaction
Oxidizing agent
the ion or molecule that accepts electrons
Reducing agent
the ion or molecule that donates electrons
Oxidation number
a concept that is used to simplify the electron bookkeeping in redox reactions
The oxidation number of an element in an elementary substance is:
(I.e. Cl₂, P₄)
0
The oxidation number of an element in a monatomic ion is:
equal to the charge of the ion
Ex: in NaCl, sodium has an oxidation number of +1 (because it has a charge of +1) and chlorine has an oxidation number of -1
(because it has a charge of -1)
Group 1 elements always have an oxidation number of ____ in their compounds
they always have an oxidation number of +1 because they always exist as +1 ions in their compounds
Group 2 elements always have an oxidation number of ____ in their compounds
they always have an oxidation number of +2 because they always exist as +2 ions in their compounds
Oxygen is ordinarily assigned an oxidation number of ____ in its compounds
-2 (except for peroxide, where the oxidation number of oxygen is -1)
The sum of the oxidation numbers in a neutral species is:
0
The sum of oxidation numbers in a polyatomic ion is:
equal to the charge of that ion
Define oxidation in terms of increasing/decreasing oxidation number
oxidation is defined as an increase in oxidation number
Define reduction in terms of increasing/decreasing oxidation number
reduction is defined as a decrease in oxidation number
Half-equation
two equations that come from a redox reaction: one for oxidation (electron loss) and one for reduction (electron gain
When balancing half-reactions, what aspects need to be balanced and in what order should you balance them?
- Number of atoms of the element being oxidized or reduced
- Oxidation number
- Charge
- Hydrogen
- Oxygen
When you are balancing the oxidation number in reduction half-equations, which side do you add electrons onto?
left
When you are balancing the oxidation number in oxidation half-equations, which side do you add electrons onto?
right
When balancing the charge of a half-equation in an acidic solution, what do you add?
H⁺ ions
When balancing the charge of a half-equation in a basic solution, what do you add?
OH⁻ ions
In order to put the two half-equations together to balance the entire redox reaction, what should you make sure cancels?
the electrons
