Unit 4 Flashcards
Solutions:
homogenous mixtures of two or more substances
Solvent
A compound of a solution that is present in the greatest amount
Solute
Any component in a solution other than the solvent (i.e, the other ingredients in the mixture)
How is a solution made?
By dissolving a solute in a solvent (solute is added to the solvent)
How are solutions described qualitatively?
As concentrated or dilute
Concentrated solutions…
have a large amount of solute compared to solvent
Dilute solutions…
have a small amount of solute compared to solvent
Saturated solution
a solution that contains the maximum concentration of a solute possible at a given temperature
Unsaturated solution
- a solution that contains less than the maximum concentration of a solute possible at a given temperature
- can dissolve more of the solute into the solution
Supersaturated solution:
a solution containing more than the maximum quantity of solute predicted to be soluble in a given volume of solution at a given temperature
Concentration units
PPM
- grams of solute per million grams of solution
- =grams of solute/grams of solution (all times 10^6)
- OR mg of solute/kg of solution
PPB
- grams of solute per billion grams of solution
- ppb=grams of solute/grams of solution (all times 10^9)
- OR micrograms of solute/kg of solution
How to find the amount of solute (moles or grams) in a given voume of solution?
Use molarity
Molarity formula
Molarity=# of moles of solute/# of L of solution
molarity formula rearranged
number of moles solute=?
(molarity)(# liters of solution)
Beer’s law
absorbance=molar absorptivity x path length x concentration of absorbing species
intensity of color can be used to measure concentrations
A (in Beer’s law)
absorbance (amount of light absorbed by sample)
E (in beer’s law)
molar absorptivity
b (in beer’s law)
path length
c (in beer’s law)
concentration of absorbing species
Stock solution
a concentrated solution of a substance used to prepare solution of lower concentration
Dilution
the process of lowering the concentration of a solution by adding more solvent
Ionic Theory of Solutions
- proposed by Arrhenius to account for the electrical conductivity of water
- proposed that certain substances produce freely moving ions when they dissolve in water, and these ions conduct electric current in an aqueous solution
Electrolytes
- An electrolye dissolves in water to give an electrically conducting solution
- most ionic solids dissolve in water
- ions in previously fixed states are free to move about, forming an electric current
Strong electrolyte properties
- Total dissociation
- Efficient conductivity
- Includes strong acids, strong bases, and soluble salts
Weak Electrolyte
- Partial dissociation
- Slight conductivity
- Weak acids and week bases
Nonelectrolyte
- no dissociation
- n/a conductivity
- includes molecular compounds
Ionic compounds in solution
- When an ionic compound is dissolved into solution, the molarity for each ion is based on how many ions there were in the salt
- For example, in an aqueous solution that is 0.1M NaCl, your solution will have 0.1M Na+ ions and 0.1M Cl- ions based on the 1:1:1 mole ratio.
- But if you have an aqueous solutio that is 0.1M Na2SO4, your solution will have 0.2M Na+ ions and 0.1M SO4 ions based on the 1:2:1 mole ratio.
H+ ions strongly associated with water molecules form…
Hydronium ions (H30+)
Acids
proton (H+ donors)
Bases
Proton acceptors
Neutralization
reaction that takes place when an acid reacts with a base a produces a solution of a salt in water
Salt
- product of a neutralization reaction
- made up of the cation of the base plus the anion of the acid
amphiprotic
acts as acid or base (ex. water)
Titration
an analytical method to determine the concentration of a solute in a sample by reacting it with a standard solution
Standard solution
a solution of known concentration (also called the titrant)
Equivalence point
point when moles of added titrant is stoichiomerically equivalent to moles of substance being analyzed
End point
point reached when the indicator changes color
Precipitation
combining an insoluable cation with an insoluable anion forms a precipitate
Oxidation
loss of electrons
reduction
gain of electrons
Redox reactions
transfer of electrons