concentrations of solutions

• a solution can have more than one solute, but there can only be one solvent in a solution
• the amount of solute dissolved in the solvent determines a substance’s concentration

there are several ways to express the concentration of a solution:

by mass

percent\,by\,mass = \frac{mass\,of\,solute}{mass\,of\,solution} * 100

by volume

percent\,by\,volume = \frac{volume\,of\,solute}{volume\,of\,solution} * 100

percent by volume is used when liquids or gases are the solute

• closely related to percent by mass (percenti s a ratio that expresses parts per 100)

ppm tells us how many parts a solute makes up of a million (10⁶) parts of a solution this also tells us the mass in mg of solute in one L of solution

parts\,per\,million = \frac{mass\,of\,solute}{mass\,of\,solution} * 10^{6} = \frac{mg\,solute}{L\,solution}

ppb tells us how many parts a solute makes up of a billion (10⁹) parts of a solution this also tells us the mass in micrograms of solute in one L of solution

parts\,per\,billion = \frac{mass\,of\,solute}{mass\,of\,solution} * 10^{9} = \frac{microgram\,solute}{L\,solution}

the unit ppm is often associated with the concentration of pollutants when measuring water quality in rivers, lakes, etc.

• a common way to express concentration
• the number of moles of solute in 1L of solution
• chemists use this more in the laboratory

molarity\,(M) = \frac{moles\,of\,solute}{liters\,of\,solution}

the unit for molarity is mol/L and is abbr as M (molar)

M_{1}V_{1} = M_{2}V_{2}

where: M₁ and V₁ represent the molarity and volume of the stock solution M₂ and V₂ represent the molarity and volume of the dilute solution

V can be any unit but has to be the same on both sides

• physical properties of solutions that are affected by the amount of dissolved solute—but not the identity of the solute
• affected by a chaange in the concentration of a solute

• the pressure exerted on the walls of a closed container by the gas particles that have evaporated from the enclosed liquid
• an increase in the concentration of a solute will cause the vapor pressure of the solution to decrease
  • an increase in solute decreases the number of solvent particles to evaporate

• the temperature when the vapor pressure is equal to the pressure exerted by the surroundings of the liquid
• an increase in the concentration of a solute will cause the boilin point of the solution to increase
  • the increased presence of solute at the surface of a liquid decreases the number of solvent particles to evaporate (more energy needed to happen)

• the temperature when molecules in the liquid phase transfer into the solid phase
• an increase in the concentration of a solute will cause the freezing point of the solution to decrease
  • the solute get in the way of the solvent particles’ abilitty to arrange as a solid form

• through the process of osmosis, the particles of water pass through the semiperemable membrane from an area of higher solvent concentration to an area of lower solvent concentration
• An increase in the concentration of a solute will cause the osmotic pressure to increase
• more water molecules will move across the membrane, increasing the pressure of the flow