Chapter 04: Chemical Quantities and Aqueous Reactions Flashcards
Stoichiometry
Quantitative relationships between products and reactants in chemical equations
Requires use of:
1) Balanced chemical equation
2) Conversion factor: mole ratios
Mole ratio
Ratio in units of moles relating any two species in a chemical reaction
Used as a conversion factor
Solving stoichoimetry problems
Mass (g) of compound A
to
Moles of compound A
using molar mass
Then to
Moles of compound B
using mole ratio
Then to
mass (g) of compound B
using molar mass
Limiting reactant (reagent)
Reactant that limits the amount of product that can be made
Excess reactant
Leftover reactant (not reacted) in a chemical reaction
Reaction yield: theoretical yield
The amount of product that would result if all the limiting reactant reacted
Reaction yield: actual yield
The amount of product that is actually obtained from a reaction
% yield
% yield = actual yield x 100
theoretical yield
Solution
Homogenous mixture of 2+ substances
Solvent
Substance present in larger amount within solution
Solute
Substance(s) present with smaller amounts dissolved in solvent
Aqueous solution
Solution with water as solvent
Solution concentration
Qualitative and/or quantitative description of amount of solute in a solvent/solution
Molarity
Molarity (M) = moles of solute (n)
liters of solution (V)
Dilute solution
Relatively small amount of dissolved solute
Concentrated solution
Relatively large amount of dissolved solute
Dilution
Procedure for preparing a less concentrated solution from a more concentrated solution
Dilution formula
M1V1=M2V2
Where M = molarity
V = volume
*moles (n) of solute remain the same
Solute and solvent interactions
Attractive forces between solute particles, between solvent particles, and between solute and solvent particles
If attractions between solute and solvent are strong enough –> dissolve
Charge distribution in water molecule
Oxygen = partial charge negative Hydrogen = partial charge positive
Hydration
Process in which an ion is surrounded by water molecules arranged in a specific manner
Electrolyte
Substance that, when dissolved in water, conducts electricity
Contain cations and anions –> dissolve into ions
(Ionic compounds, some acids, some bases)
Nonelectrolyte
Substance that, when dissolved in water, does not conduct electricity
No cations, no anions
(Molecular substances)
Strong electrolyte
Dissolve completely as ions
*Irreversible reaction.
Most salts, some acids and bases
Weak electrolyte
Do not dissolve completely as ions
*Reversible reaction
Dissociation
Ions of a salt separate as salt dissolves
Ionization
Process of ion formation in solution
Results from chemical reaction between water + compound
(acids, bases)
Soluble
A compound that dissolves in water
Insoluble
A compound that does not dissolve in water
Solubility
The maximum amount of solute that will dissolve in a given quantity of solvent at a specifc temperature
Precipitation reactions & preciptate
Reactions that produce precipitate
&
An insoluble solid that separates from solution
Spectator ions
Ion that exists in the same form on both sides of chemical reaction
Complete ionic equation
Molecular equation’s aqueous solutions are broken down to ions
Solids, liquids, and gases are still written as compounds
Net ionic equation
A complete ionic equation with spectator ions cancelled out
A shorthand way of showing what ions react
Gravimetric Analysis
Make aqueous solution with unknown substance
React unknown with known –> form precipitate
Filter & dry precipitate
Weigh precipitate
Use chemical formula and mass of precipitate to determine amount of unknown ion
Acid properties (6)
- sour taste
- blue litmus paper –> red (red means acid)
- reacts with certain metals to produce H2 (g) (as H is less reactive than most metals and displaced)
- reacts with carbonates and bicarbonates to produce CO2 gas
- reacts with bases to produce salt and water (neutralization)
- aqueous acid solutions conduct electricity
Base properties (5)
- bitter taste
- feel slippery
- red litmus –> blue (blue means base)
- reacts with acids to produce salt and water (neutralization)
- aqueous base solutions conduct electricity
Arrhenius acid
Produces H+ (H3O+) in water
Arrhenius base
Produces OH- in water
H3O+
Hydronium ion
Hydrated proton (i.e. H+ + H2O)
(Remember: H+ has 0 electrons, 0 neutrons, 1 proton)
Brønsted acid
Proton donor (donor = acid)
Must contain at least one ionizable proton
Brønsted base
Proton acceptor (acceptor = base)
Acid ionization
Acids = molecular compounds Ionization = ion formation in solution from compound + H<sub>2</sub>O reaction
Thus:
- Acid molecules are pulled apart by attraction for water
- When acids ionize, H+ and counter anions form
- % of acid molecules that ionize varies
Strong acids
Acids that ionize virtually 100%
(Irreversible)
Weak acids
Ionize only a small percentage
(Reversible)
Monoprotic acids
Each unit of acid yields one H+ ion
Diprotic acids
Each unit of acid yields two H+ ions
Triprotic acids
Each unit of acid yields three H+ ions
Neutralization reactions
Acid + base –> salt + water
Weak acid + base –> salt + water
Gas-evolving reactions
Reactions that form gas directly (from ion exchange) or indirectly (from decomposition; reactants –> ion exchange –> gas + water)
acid + salt –> salt + gas + water
compared to
acid + base –> salt + water
Compounds that undergo gas-evolution reactions (4)
Sulfides –> H2S (g)
(Bi)carbonates –> H2CO3 –> CO2 (g)
(Bi)sulfites –> H2SO4 –> SO2 (g)
Ammonium –> NH4OH –> NH3 (g)
Oxidation-reduction reactions
(Redox reactions)
Electron transfer reactions
Uses chemical “bookkeeping” of election transfers
Oxidation half-reaction
Shows the loss of electron(s)
OIL = oxidiation is loss [of elections]
Reduction half-reaction
Shows the gaining of electron(s)
RIG = reduction is gaining [of electrons]
Oxidation reaction
Half-reaction that involves loss of electron(s)
Reduction reaction
Half-reaction that involves gain of electron(s)
Oxidizing agents
Oxidizing agents are reduced and gain electron(s)
RIG = reduction is gain –> oxidizing agent reduces
Reduction agents
Reducing agents are always oxidized and lose electron(s)
OIL = oxidization is loss – reducing agents oxidize
Combination reaction
Type of redox reaction
A + B –> C
Decomposition reaction
Type of redox reaction
C –> A + B
Combustion reaction
Type of redox reaction
A + O2 –> B
Substance + O2 –> [1+ O-containing substances] + water
Emits heat (exothermic)
Displacement reaction
Type of redox reaction
A + BC –> AC + B
3 subtypes:
- *Hydrogen** displacement
- *Metal** displacement
- *Halogen** displacement
Activity series for halogens
F2 > Cl2 > Br2 > I2
Note: order from top to bottom = decreasing activity
Note: diatomic!
Disproportionation reaction
Type of redox reaction
Same element is simultaneously oxided and reduced
Titrations
Measure the volume of one reagent required to react with a measured mass or volume of another reagent
- *Often** used to determine amount of acid or base in sample
- *Also** used for redox reactions
Buret drips into Erlenmeyer flask
Indicator
Used in titrations to indicate when amount of known substance has neutralized unknown
Endpoint (equivalence point)
When an acid and base have become neutralized
Modified dilution equation
MacidVacid(# of H+) = MbaseVbase(# of OH-)