Unit+6+-+Solutions+and+Solubility

= __Unit 6 – Solutions and Solubility__ =

a. Intermolecular Forces
__**Intramolecular forces:**__ the forces inside a molecule that keep the individual atoms attached to one another //ex) covalent and ionic bonds// __**Intermolecular forces:**__ attract or repel molecules to one another

//*Side note*// By analyzing the Lewis structure of water we're led to the conclusion that it's a strongly polar molecule; we could reach the conclusion that polarity plays a role in solubility. We could test the hypothesis that like-dissolves-like by dissolving polar solute in polar solvent and non-polar solute in non-polar solvent.

__**Intermolecular Forces**__

Occurs in a networked lattice (which is a sophisticated repeating pattern called a crystal structure) of oppositely charged, and thus attracted, particles.
 * //Ionic Bond//**

//**London Dispersion**// Attracts all particles towards one another, if you can imagine an electron cloud around each nucleus, occasionally a shift will occur (more electrons on one side than the other) momentarily creating a polarized state where opposite charges on each particle attract. //*__extremely__ weak*//

//**Dipole - Dipole**// An attractive force between polar molecules; whenever electrons are unequally shared in a covalent bond, a polar bond exists, this polar bond creates an apparent partial charge on either end. //*the attraction of oppositely charged ends of molecules* Special type of dipole - dipole interaction; Hydrogen atoms on one water molecule are attracted to the electron density of lone pairs on neighboring molecules //*much stronger than Dipole - Dipole or London Dispersion*// Any substance that includes a hydrogen covalently bonded to a **N, O,** or **F** atom can "hydrogen bond" to it's own molecules to increase the effect of the dipole - dipole interaction
 * Hydrogen Bond**//

__**Polarity and Hydrogen Bonds**__ Ethylene glycol is highly soluble in water; the theoretical explanation for this is: Polar solute molecules are surrounded and suspended in solution by Polar Solvent Molecules.

b. Using State Notation
-When writing equations, we must take care to note the solvents being used. -Some reactions will not occur without water, we should note that it is required. -This notation is critical when we analyze energy, enthalpy, and entrapy. -A small, bracketed subscript follows each formula in a chemical equation indicating its state. -Only one subscript is allowed per formula. -(s)=solid -(g)=gas -(l)=liquid -(aq)=aqueous (a solution dissolved in water) -(al)=dissolved in alcohol (tincture)

//Example:// Ammonia gas dissolved in water = NH 3(aq) //Example:// Solid iodine dissolved in alcohol = I 2(al) //Example:// Water vapour = H 2 0 (g)

c. Making solutions
To describe the amount of solute in a solution you must calculate the ratio concentration. To do so, use the following formula: concentration= quantitiy of solute /quantity of solution //Example 1:// 15 g of salt is dissolved in 42.0 g solution of water, what is the concentration?

To calculate the percent concentration of a substance, use the following formula: concentration= __volume of solute__ x 100 volume of solution //Example 2:// A photographic "stop batter" contain 140 mL of pure acetic acid in a 500 mL bottle of solution, what is the percent solution?

To calcuate the percent concentration in terms of weight and volume, use the following equation: concentration= __weight of solute__ x 100 volume of solution //Example 3:// 17 g of salt is disolved in 100 mL of water, what is the percent concentration?

To calculate the percent concentration in terms of the weight of solute and solution, use the following formula: concentration= __weight of solute__ x 100 weight of solution //Example 4:// A sterling silver ring has a mass of 12 g and contains 11.1 of pure silver. What is the % weight by weight concentration of silver in this substance?

Small quantities of solution are measured in ppm. The following is a list of ratio equivalents to ppm: ppm= mg/L =g/10^6 ml =g/1000L =mg/kg =mg/g //Example 5:// Dissolved oxygen in natural waters is an important measure of the health of the ecosystem. In a chemical anaylysis of 250 mL of water, 2.2 mg of oxygen was measured. What is the concentration of oxygen in ppm?

To measure a substance's initial and final concentration or volume, use the following formula: (C1)(V1)=(C2)(V2) //Example 6:// A student has 50mL of a concentrated solution of hyrdrogen peroxide(3.0M); if she adds 100 mL of water to this mixture; what will be its new concentration?

To calculate the molarity of a substance, use the following formula: Molarity= __amount of solute(in moles)__ amount of total solution(in L) //Example 7:// In a quantitatvie analysis, a stoichiometric calcuation produced 0.186 mol of sodium hydroxide in 0.251L of solution. Calculate the molariy of sodium hyroxide.

//Example Answers:// **1.** //0.36// **2.** //28%// **3.** //17%// **4.** //92.5%// **5.** //8.8 ppm// **6.** //1.0 M// **7.** //0.744 M//