chem 30 solutions
solution
homegenous mixture of two substance: a solute and a solvent
solute
substance being dissolved, present in lesser amount
solvent
substance doing the dissolving, present in larger amount
what states of matter can a solute and solvent be
any
how do solutions form
between solute and solvent molecules because of similarities between them (like dissolves like)
why do ionic solids dissolve in water
because the charged ions (polar) are attracted to the polar water molecules
what dissolves in what
non polar in nonpolar, polar in polar
what solutions are conductors and which are not
conductor: containing ions
non conductor: containing molecules
electrolytes
substances that dissolve in water to form ions. ions formed from these conduct electric current in a solution
strong electrolytes
in water, contain many ions. make the light bulb on conductivity appartus glow brightly. ionic substances are strong electrolytes
weak electrolytes
contain only a few ions. make lightbulb on conductivity apparatus glow dimly. weak acids and bases that dissolve in water and produce few ions are weak electrolytes
non-electrolytes
substances that do not form any ions in solution. bulb on conductivity apparatus does not glow. covalent molecules that dissolve in water but do not form ions (i.e. sugar) are non electrolytes
what compounds are strong acids
group 1 and 2 metal compounds
solubility
maximum amount of solute that can be dissolved in a given amount of solvent, affected by type of solute, type of solvent, and temperature. measured in g of solute per 100 g solvent at given temp
unsaturated solution
does not contain the maximum amount of solute in it, at a given temperature
saturated solution
contains the maximum amount of solute in it at a given temperature
supersaturated solution
contains more than the maximum amount of solute in it at a given temperature. unstable: dust, vibrations or extra solute added can cause all excess solute to precipitate out. made at higher temps then cooled down, if no solute settles out it is supersaturated
how to increase solubility of solids in water
increases as temperature increases
when does solubility of gases in water decrease
when temperature increases. at higher temps since more gas molecules have the energy to escape from solutions
molarity
most common unity of concentration used. defined as moles of solute/ liters of solution= M
how to prepare a solution
1. amount of solute weighed out, added to flask
2. portion of solvent added to volumetric flask
3. mixture is swirled unitl all solute is dissolved
4. additional solvent added up to the mark on the flask
dilution
solutions prepared from more concentrated ones by adding water. when more water is added, the volume increases, causing a decrease in concentration, but amount of solute does not change
what does the amount of solute depend on dilutions
concentration and volume of solution
dilution formula
M1V1=M2V2
ion concentration
concentration of ionic substances in solution reflects the concentration of the solute before it dissolves. concentration of ions dissolved in solution calculated by noting number of each ion present in the formula unit
percent concentration
amount of solute dissolved in a certain amount of solution.
concentration = amount of solute/amount of solution
mass percent
mass of solute/mass of solution x 100
mass of solution= mass of solute + mass of solvent
mass/volume percent
(m/v)= mass of solute/volume of solution x 100
volume/volume percent
volume of solute/volume of solution x 100
how can percent compositon be used
in the preparation of solutions, you need to calculate the amount of solute or solution. to achieved this, percent composition can be used as a conversion factor. ex) 15%=15g/100gsolution
colligative properties
properties of solutions that depends on the number of particles dissolved in solution. some important colligative properties are vapor pressure lowering, freezing point depression and boiling point elevation.
freezing point depression
addition of solute to a solvent lowers its FP. proportional to the amount of solute in a solution. the solute interferes with the IMFs that bring the solvent particles together at the FP. solution must be well below normal FP to form solid
boiling point elevation
addition of a solute to a solvent increases its boiling point. proportional to amount of solute in a solution.
vapor pressure
pressure of a gas above a liquid at a certain temperature. at a certain temp, gas and liquid molecules for a substance are in dynamic equillibrium (rate of vaporization = rate of condensation)
what is the effect of a solute on the VP of the liquid into which it dissolves
when a solute is added to a liquid, the solute particles interfere with the ability of the solvent particles to vaporize. as a result, the VP of the liquid is lowered by the addition of solute- BP increases
very low concentration
used for water quality where to be safe Pb, Hg compounds etc. have to be very low.
ppm= parts per million, 2ppm= 2 molec in 1mil molec
ppb= parts per billion