solubility chapter 2 ms. mishriky & m. moscoso. a solution is a mixture review: separation...

Solubility

Chapter 2Ms. Mishriky & M. Moscoso

A solution is a mixture

• Review: Separation Techniques of Mixtures– Decantation– Magnetism– Evaporation– Distillation– Filtration– Sieving– Sedimentation– Hand removal

Solutions

Definition:Definition: a solution is a homogeneous mixture whose component substances cannot be distinguished, even with the aid of a magnifying instrument.

- can be solid, liquid or gas.The component substances are called solvent and

solute. The solute is dissolved in the solvent. Solute molecules fit into “holes” of solvent.

Aqueous solution: solution in which the solvent is water.

Solutions• An aqueous solution is a solution in which the

solvent is water. • It is the polarity of the water molecule that

makes it capable of dissolving a great number of substances.

• In general, water dissolves molecules made up of ionic bonds (like salt) and those that have a certain polarity (like sugar).

• Conversely, non-polar molecules are not very soluble in water.

How does that work?

Properties of Solutions

• Solubility• Concentration• Electrical conductivity• pH

Solubility

• Solubility: it is the maximum amount of solute that can be dissolved in a certain amount of solvent, at a certain temperature.

• “Like dissolves like”: A solution forms when the attractive forces between the solute and the solvent are similar (polar & polar, non-polar with non-polar).– Solubility in water: solutes that are polar (Na+Cl-) dissolve best in

water. Solutes that are non polar (oil) almost never dissolve in water.

– http://www.mhhe.com/physsci/chemistry/essentialchemistry/flash/molvie1.swf

Factors that influence solubility

• Nature of the solute• Nature of the solvent• Pressure (gas solutes)• Temperature

Solubility is expressed inmg/L.

Saturation of solutions

• Saturation: saturation is the point at which a solvent can dissolve no more of a solute and additional amounts of solute will appear as a precipitate.

• 36 grams of salt is fully saturated in 100 ml of water.

36.0

Supersaturated solution

• Undersaturation: is a state of a solvent that is capable of dissolving more solute (under certain conditions).

• Saturation: saturation is the point at which a solvent can dissolve no more of a solute and additional amounts of solute will appear as a precipitate.

• Supersaturation: To cause a solution to have more solute dissolved in the solvent than it can stably contain (under certain conditions).