Solutions Unit Flashcards
What is a solution?
A homogeneous mixture
What is a mixture?
A combination of 2 or more substances, not chemically combined
How can mixtures be seperated?
Some by filtration if the particles are big enough, others by evaporation or distillation (if the boiling points are different)
What is a homogeneous mixture?
It is a mixture that is the same all throughout
What is a heterogeneous mixture?
A mixture that is not uniform
What is a solute?
The dissolved substance in the solution (or the part in lesser amount)
What is a solvent?
The part of a solution in which the solute is dissolved (or the part in greater amount)
What is an aqueous solution?
A solution in which water is the solvent
What are the properties of a solution?
- homogeneous
- dissolved particles will not come out of the solution if left standing
- clear and transparent
the solute and solvent cannot be separated by filtration
What are the types of solution?
Gas (ex air), liquid (ex NaCl aq), solids (ex metals, amalgams and alloys)
What is concentration?
A ratio of solute to solvent
What is a concentrated solution?
One which has a large amount of solute dissolved per unit of solvent
What is a dilute solution?
One which has a small amount of solute dissolved per unit of solvent
What is solubility?
How much solute can dissolve in a particular solvent under given conditions of temperature and pressure.
What is a saturated solution?
One which the solvent has dissolved all the solute it can hold at given conditions.
What is an unsaturated solution?
One which the solvent has not yet dissolved all the solute it can hold
What are the factors that affect solubility?
Temperature: for ionic substances (salts) an increase in temperature will increase the solubility. For gases, an increase in temperature lowers solubility.
Nature of the solute and solvent: like dissolves like, polar dissolves polar (and ionic), non-polar dissolves non-polar.
Pressure (for gases only): The higher the pressure the greater the solubility
What conditions are gases most soluble at?
High pressure and lower temperature.
What are the factors affecting rate of solution?
- Size of the particles
- Stirring
- How much of the solute is already dissolved
- Temperature
What is a precipitate?
A solid that forms suddenly in a solution as a result of a chemical reaction or a change in solubility.
What are colligative properties?
Properties that depend on the number of particles in a solution (not on the identity of the solute).
What do colligative properties include?
Freezing point depression and boiling point elevation.
What is freezing point depression?
Adding a solute to a solvent lowers the freezing point of the solution. (the solution has a lower freezing point than the pure solution)
What is the relationship between number of particles and freezing point?
The higher number of particles, the lower the freezing point.
What is molality?
Another method of calculating concentration.
moles of solute/kg of solvent
Formula for calculating freezing point depression:
∆Tf = Kf x m
What is Kf for water?
1.86 1.86 C/molal
What are non electrolytes?
Substances which dissolve but do NOT dissociate in water.
Why is this?
Because they do not produce ions i solution, they do not conduct electricity.
What are electrolytes?
Substances which dissociate in water. They produce ions in a solution and DO conduct electricity. They are mostly ionic compounds.
What will one mole of a electrolyte produce?
More than one mole of ions/particles.
What will one mole of a non-electrolyte produce?
One mole of particles in a solution.
What is the formula for freezing point depression for electrolytes?
∆Tf = Kf x m x number of mole of particles/ions in the solution.
Of the following, which is an example of an electrolyte?
C6H12O6
(NH4)3PO4
(NH4)3PO4 because it is ionic.
How do you calculate ppm?
ppm = mass of solute/mass of solution x 1000000
How do you solve dilution problems?
Use the formula (Vi)(Mi) = (Vf)(Mf) and remember to subtract.
