High School Chemistry/Solutions, Acids, & Bases

All matter is made up of atoms that have mass and occupy volume (or space).

Matter is broken down into pure substances (homogeneous matter) and mixtures (heterogeneous matter). A homogeneous matter (Pure Substance) is where the composition is organized while a heterogeneous matter (Mixture) is where the structure is not organized.

Pure substances are broken down into elements (H₂ and Cu) and compounds (H₂O, NaCl_(s)) and they are mostly made up of only one atom. Mixtures are broken down into more categories that we will dive right in to!

Mixtures

A homogeneous mixture is a mixture where there is a rigid structure. A heterogeneous mixture is a mixture which is unequally distributed and has no structure.

Pepper and salt poured onto each other make a heterogeneous mixture, where there is no defined composition. Vinegar is an example of a homogeneous mixture, and not a pure substance since water, its solute, is dissolved in the solvent, being acetic acid. Homogeneous mixtures are also known as solutions, which are mostly composed of liquids (including vinegar), but can include gases.

Phases are termed as samples that have a rigid composition. A homogenous mixture only consists of one phase, while a heterogeneous mixture is made up of 2+ phases. An example is when oil and vinegar are mixed together, forming layers/phases. Thus, oil and vinegar mixed together both make a heterogeneous mixture.

Homogeneous mixtures are broken down to solutions, with solutions possessing the tiniest particles of the mixtures. The solids are alloys, the liquids are acqueous solutions (like NaCl_(aq)), and the gases are matter like air. Air is where gases, like O₂, are dissolved in nitrogen. Alloys are a mixture of 2+ elements, which at least one of them is a metal. A solution's particles cannot be separated through a filter paper since their particles are too small.

Now, for the rest of the heterogeneous mixtures: Colloids are heterogeneous mixtures which contain particles that are bigger than solutions, the tiniest particles, and smaller than suspensions, the biggest particles. Colloids possess a milky or misty appearance and they exhibit the Tyndall Effect. The Tyndall Effect is where the particles of light are scattered by the colloids. You can observe this by witnessing sunlight passing through a colloid known as fog. A colloid's particles will also not settle to the bottom and will be suspended for an indefinite period of time, an example being milk. This difference is what separates colloids and suspensions.

Suspensions are heterogeneous mixtures who possess the biggest particles of the mixtures. Their particles remain suspended for only a short amount of time, before settling to the bottom (as a result of their large-particle size).

Solubility

1. Soluble - Solute will dissolve in solvent (aq)
2. Insoluble - Solute will not dissolve in solvent (s)
3. Solubility - The degree to which a solute dissolves in a solvent

Solvents move from an area of low concentration to high concentration (osmosis). Solutes move from an area of high concentration to low concentration. A dilute is a solution that doesn't have a lot of solutes dissolved, while a concentration is a solution that has a lot of solutes dissolved.

1. Unsaturated - The solute is dissolved but more solute can be added.
2. Saturated - All solute is dissolved, no more are able to be added.
3. Super Saturated - The solute is dissolved and there is more undissolved solute in the solution (too much).

You will be taught how to read a solubility curve, a graph which showcases how much solute can be dissolved [in a solution] at different temperatures. You should be able to determine whether a solution is unsaturated, saturated, or supersaturated at a given temperature.

Dissolution

Factors [AMOUNT]

1. Composition of the solute and solvent ("like dissolves like")
2. Pressure: Gases (P ↑ S ↑)
3. Temperature (T ↑ S ↑ [solids]; T ↑ S ↓ [gases])

Factors [RATE]

1. Surface Area, as more SA increases the interactions between the particles of the solute and the solvent.
2. Stirring/Agitation, as it spreads out the solute particles and brings in new solute with new solvent particles.
3. Temperature, as it increases the dissolving of the solid solute in the liquid solvent.

Mathematical Formulas

Mass Percent

Mass solute (g)

---

Entire solution (g)

Molarity

moL of the solute

---

entire Liter of solution

Dissolution

M₁V₁=M₂V₂

Colligative Properties

Definition: Properties of a solution which are affected by the amount of dissolved solute presented in the solution

• Vapor Pressure decreases as adding solute to solvent always has this effect.
• Boiling Point increases. Recall that liquid boils when the VP is equal to the atmospheric pressure. Since VP is already decreasing, the solvent's temperature must be really high in order to equal the VP to the atmospheric pressure.
• Freezing Point decreases as the addition of the solute interferes with the intermolecular forces in the solvent needed during solidification.

Titration

How to prepare a solution from concentrated stock solution

1. Use M₁V₁ = M₂V₂ to find the volume of concentrated stock solution needed.
2. Measure [9.4mL] stock solution and pour into a [1.5L] size volumetric flask.

How to prepare a solution from a solid solute

The task is to prepare 200. mL of .5M of KNO₃

1. Use m=mol/L to calculate the moles of the solute. (get moles)
2. Convert the moles to grams to measure. (--> g)
3. Use the triple beam balance to mass out the needed solute (g). (measure grams in a triple beam balance)
4. Obtain [200. mL] volume flask and add the solute to it. (obtain the desired volume [volumetric flask] and add the solute to it)
5. Add dH₂O up to the line and mix. (add distilled water 'till line and mix)