Solution Chemistry

Solutions are special kinds of mixtures

Let’s review!!

Element – pure substance homogeneous throughout only one kind of matter present

Compound – pure substance homogenous throughout made from 2 or more elements chemical in nature

Mixture – can be homogeneous or heterogeneous made from 2 or more elements, compounds, or both physical in nature

Because solutions are mixtures they have two parts:

solutes thing being dissolved most often a solid, but can be any state

think: SODA

solvents thing doing the dissolving most often a liquid – water for instance – but can be any state

think: our atmosphere – NITROGEN

Dissolving does not mean a change in state. Solutes do not melt! They remain a solid (if they are a solid to begin with)

Polarity – the uneven distribution of charges on a moleculeuneven distribution is a result of:

a. Sharing of electrons between atoms with different energy

1. Asymmetric molecules are polar

Electrons are veryPresent on this sideOf the molecule

That makes this sideOr pole of the moleculeFeel negative

This side or pole of theMolecule has no Electrons present.The charge of the nucleusIs felt making it feelpositive

Hydrogen has one electron on the K shellFluorine has 9 electrons on the K and L shells. Fluorine is a larger atom withMore energy. F controls all of the electrons.

In the water molecule, hydrogen is a smaller atom with less energy than oxygen.When the electrons are share between these two atoms, oxygen controls the electrons because it is an atom with more energy.

Because of this the molecule has two poles – one that feels positive (hydrogen’s end) and the other that feels negative (oxygen’s end).

Molecules can also be nonpolar – an even distribution of charge on the molecule. a. Sharing of electrons between atoms of equal energy

1. Diatoms

Here this diatom, electrons are on the same energy level. Electrons are on the sameenergy shells and therefore are controlled equally by each atom. Electrons spin equally around each nucleus.

2. Symmetric molecules

Well how does all this connect with solutions? The reason why solutes stay in solutionis because of polarity. Polar solutes dissolve most easily in polar solvents – water is polarand so it can dissolve all polar molecules. Nonpolar solvents dissolve nonpolar solutes.

NaCl

NaCl is an ionic compoundthat is made up of + Naions and - Cl ions.NaClWhen an ionic compounddissolves in water it is called DISSOCIATION.

Na +Na +

Na +

Na +

Na + Na +

Na +Na +

Na +

Na +

Na +

Na +Na +

Na +

Na + Na +

Na +

Cl -

Cl -

Cl -

Cl -

Cl -

Cl -

Cl -

Cl -Cl -

Cl -

Cl -

Cl -

Cl -

Cl -

Cl -

Cl -

Cl - Cl -

Cl -Cl -

If a non polar molecule is put into water, it will NOT dissolve because of the like Charges that will meet in the water and the solute.

CH4 is a symmetricmolecule that is non polar. It will notdissolve in waterbecause it will be repelledby the positive pole ofthe water molecule.

Solubility – the ability of a solvent to dissolve a solute.

Solubility will be affected by: pressure temperature

particle size – the smaller the particles of solute the easier it will fit into the

spaces of the solvent. stirring – moving the solute around pushes particles into solution.

Affects molecular distance of solvent.The larger the MD, the more solute thatcan be dissolved, and vice versa.

Temperature:

Pressure:

There exists two types of solutions ( well there really are more but that’s all we’re going to talk about)

a. Saturated Remember, solubility and therefore saturation is

b. Unsaturated dependent on temperature of solvent!!

**On solubility chart, saturation is marked anywhere on the graphLine. Unsaturation is the area under the graph line.**

Concentration: the amount of solute dissolved in a GIVEN amount of solvent.

Dilute – a little bit of solute in a specific amount of solvent.

Concentrated – a lot of solute in the SAME amount of solvent.

Special solutions

Suspensions• Made of solute/solvent• Heterogeneous • Solute is suspended in the

solvent for a period of time• Solute will eventually settle

out of solution• Oil and vinegar• Chocolate milk• Sand and water

Colloids• A special kind of suspension

where the solute is held in the solvent for an extended time period.

• Homogeneous • The use of an emulsifier is

needed to keep the solute in suspension.

• Mayonnaise• Whipped cream

Acid base comparisonacid

• Any aqueous solution that releases Hydrogen ions in solution.

• Generally, any compound that contains Hydrogen

• Will react with metals to release Hydrogen gas.

• Has a pH between 1 and 6.9• Tastes sour• Turns blue litmus red• Will react with a base to

produce a salt + water

base

• Any aqueous solution that releases hydroxyl ions (OH) in solution.

• Generally, any compound that contains the OH ion.

• Has a pH between 7 and 14• Tastes bitter• Feels slippery• Turns pink litmus blue.• Will react with an acid to

product a salt + water.

Acid: hydrochloric acid – HCl stomach acid sulfuric acid - H2SO4 car battery acid nitric acid HNO3 fertilizers carbonic acid H2CO3 acid found in sodas

Bases: sodium hydroxide – NaOH Drano human blood potassium hydroxide – KOH soaps calcium hydroxide – Ca(OH)2 hair relaxer, remover, Ca supplement in baby food.

Neutralization reaction: Acid + base = salt + water HCl + NaOH NaCl + HOH pH 2 pH 14 pH 7 pH 7