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)

The charge of the nucleus Is felt making it feel positive Polarity – the uneven distribution of charges on a molecule uneven distribution is a result of: a. Sharing of electrons between atoms with different energy 1. Asymmetric molecules are polar Electrons are very Present on this side Of the molecule That makes this side Or pole of the molecule Feel negative This side or pole of the Molecule has no Electrons present. The charge of the nucleus Is felt making it feel positive Hydrogen has one electron on the K shell Fluorine has 9 electrons on the K and L shells. Fluorine is a larger atom with More 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 same energy 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 Well how does all this connect with solutions? The reason why solutes stay in solution is because of polarity. Polar solutes dissolve most easily in polar solvents – water is polar and so it can dissolve all polar molecules. Nonpolar solvents dissolve nonpolar solutes. NaCl Cl - Cl - Na + Na + Cl - Cl - Cl - Na + Na + Na + Cl - Na + Na + Cl - NaCl is an ionic compound that is made up of + Na ions and - Cl ions. NaCl When an ionic compound dissolves in water it is called DISSOCIATION. Cl - Cl - Na + Cl - Na + Na + Na + Na + Cl - Cl - Cl - Na + Cl - Cl - Cl - Cl - Cl - Na + Cl - Na + Na + Cl - Na +

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 symmetric molecule that is non polar. It will not dissolve in water because it will be repelled by the positive pole of the 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 that can 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) Saturated Remember, solubility and therefore saturation is b. Unsaturated dependent on temperature of solvent!! **On solubility chart, saturation is marked anywhere on the graph Line. 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 Colloids 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 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 comparison base acid 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 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