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3.7Properties of Substances and Mixtures

Solutions and Mixtures — AP CHEMISTRY Revision Notes & Topical Questions

5 min read 8 parts Lesson 12 of 20 1 quiz

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Lesson summary

3.7 Solutions and Mixtures — Notes — AP CHEMISTRY notes: Distinguish solutions from heterogeneous mixtures and calculate with molarity and dilution.A solution (homogeneous mixture) has uniform composition and properties at the particle level.Solutions can be solid (alloys), liqui…

  • Molarity (M)
  • Amount of solute
  • A 0.10 M CaCl2 solution gives [Ca2+]
  • Volumetric flask
  • Solutions can be solid (alloys), liquid or gaseous (air)
  • A heterogeneous mixture has properties that depend on location, with visible regions or phases, such as sand in water

Section 1 of 8Solutions and mixtures

1
A solution (homogeneous mixture) has uniform composition and properties at the particle level.
2
Solutions can be solid (alloys), liquid or gaseous (air).
3
A heterogeneous mixture has properties that depend on location, with visible regions or phases, such as sand in water.
4
The solvent is the component present in the larger amount, often water; the solute is the substance dissolved.
5
The components of a solution cannot be separated by filtration because the solute particles are dispersed at the molecular or ionic level.

Section 2 of 8Molarity

Molarity (M)
Molarity (M) moles of solute ÷ litres of solution, which is solution volume, not solvent volume.
Amount of solute
  • Amount of solute n = M × V, and mass = n × molar mass.

Section 3 of 8Ion concentrations

1
Soluble ionic compounds dissociate completely.
2A 0.10 M CaCl2 solution gives [Ca2+]
0.10 M and [Cl−] = 0.20 M.

Section 4 of 8Dilution

Dilution
Moles of solute are conserved on dilution, so M1V1 = M2V2.
A dilution diagram shows the same number of solute particles in a larger volume.

Section 5 of 8Preparing solutions

  • Solutions are prepared accurately in a volumetric flask calibrated to contain one exact volume.
TaskFormulaEquipment
Make from solidn = MV; m = nMBalance, volumetric flask
DiluteM1V1 = M2V2Pipette, volumetric flask
Find molesn = MVVolume must be in litres
  • Add acid to water when diluting concentrated acids.

Section 6 of 8More from the specification

1Stationary phase
  • The solid or liquid phase fixed in place in chromatography.
2Mobile phase
  • The solvent or gas that moves through the stationary phase.
3Hydrogen bonding
  • A strong attraction between molecules containing –OH groups.
4Column chromatography
  • Separation using a column of solid stationary phase and liquid mobile phase.
5Chromatography
  • Method separating substances by their different solubilities in a solvent.
6Distillation
  • Separating a liquid from a solution by boiling and condensing the vapour.

Section 7 of 8Key terms

TermMeaning
SolutionHomogeneous mixture of solute and solvent.
SoluteSubstance dissolved in a solution.
SolventComponent present in the larger amount.
MolarityMoles of solute per litre of solution.
Heterogeneous mixtureMixture with properties that depend on location.
Volumetric flaskGlassware calibrated to contain one exact volume.

Section 8 of 8Exam technique

1
Using the volume of solvent in the molarity calculation — use the volume of solution
2
Saying dilution changes the moles of solute — it only changes the volume
3
Forgetting that ionic compounds release more than one ion per formula unit
4
Not converting millilitres to litres

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