the blog

nobody blogged so i decided to do it anyways.

today we took the pop quiz that everyone failed including top ten chem student in shelby county michael scully (congrats on the award we know the quiz was a fluke). also the answers to all the homework problems were put on the board and everyone copied them down. if you have any issues use the email and be ready for any more disastrous quizzes in the future.

4.7.10.

Sorry the blog took so long to get up, the rain and everything messed with my computer and it kept crashing on me. But here you go.

The seperation of ions that occurs when an ionic compound dissolves is dissociation.
see book for example equations.
review book pg 436 example problem A.

Although no ionic compound is completely insoluble, compounds of very low solubility can be considered insoluble for most practical purposes.

GENERAL SOLUBILITY GUIDELINES -
1. Sodium, potassium, and ammonium compounds are soluble in water.
2. Nitrates, acetates, and chlorates are soluble.
3. Most chlorides are soluble, except those of silver, mercury (I), and lead. Lead(II) chloride is soluble in hot water.
4. Most sulfates are soluble, except those of barium, strontium, lead, calcium, and mercury.
5. Most carbonates, phosphates, and silicates are insoluble, except those of sodium, potassium, and ammonium.
6. Most sulfides are insoluble, except those of calcium, strontium, sodium, potassium, and ammonium.

NOTE:
To decide whether a precipitate can form, you must know the solubilities of those two compounds.

Net Ionic Equation -
includes only those compounds and ions that undergo a chemical change in a reaction in an aqueous solution.
see book pg 439 for example equation.

Spectator Ions -
ions that do not take part in a chemical reaction and are found in solution both before and after the reaction.
see book pg 439 for example equation.

review example problem B, pg 440.

ionization -
ions are formed from solute molecules by the action of the solvent in a process called ionization.

When a molecular compound dissolves and ionizes in a polar solvent, ions are formed where none existed in the undissolved compound.

Hydrogen chlorie, HCl, is a molecular compound that ionizes in aqueous solutions. It contains a highly polar bond. The attraction between a polar HCl molecule and the polar water molecules is strong enough to break the HCl bond, forming hydrogen ions and chloride ions.
see book pg 441 for example equation.

The Hydronium Ion -
some compounds ionize in an aqueous solution to release H+. The H+ ion attracts other molecules or ions so strongly that it does not normally exist alone.
see book for example equation pg 441.

The H3O+ ion is known as the hydronium ion.

Substances that yield ions and conduct an electric current in solution are electrolytes.
Substances that do not yield ions and do not conduct an electric current in solutions are non-electrolytes.

Strong Electrolyte-
is any compound whose dilute aqueous soltions conduct electricity well; this is due to the presence of all or almost all of the dissolved compound in the form of ions.

Weak Electrolyte -
is any compound whose dilute aqueous solutions conduct electricity poorly; this is due to the presence of a small amount of the dissolved compound in the form of ions.

STRONG AND WEAK ELECTROLYTES DIFFER IN **THE DEGREE OF IONIZATION OR DISSOCIATION.**

Have a good night guys.
Colby & Co.

Tuesday, April 6

Today in Dr. B's class we handed in our homework whch was #7-15 (additional problems). Dr. B then handed back the test on chapter 10 & 11, the test is out of thirty (27 on the scantron, 3 written answers). After we looked over the test Dr.B assigned the rest of the additional problems for homework. Thats pretty much it.

Blog?

Was there no blog for tonight, because I need posts and we're running shorter and shorter on time..

Friday, March 26th

Molarity and Molality

(M) Molarity- number of mols of a solute dissolved in one liter solution

(m) Molality- number of mols of a solute dissolved in one kilogram solvent
One Molal Solution- one mol solute dissolved in one kilogram solvent





also the lab will be collected on Monday

March 25th, 2010

Here are the R values for everyone--

• Justin and Griff--0.07563
• Joe and Ben-- 0.07718
• Taylor and Nick-- 0.0727
• Henry and Evan-- 0.06379
• Matt Orians and Kyle-- 0.06697
• Charlie and Chris-- 0.0814
• Ryan and Jim-- 0.07667
• Donnie and Colby-- 0.07833
• Alex and Jacob-- 0.06356
• Will Long and Matt Johnson-- 0.07997
• Riley and Patrick Blose-- 0.07383
• Matt Farrel and Andrew Parmenter-- 0.06745
• Patrick "The Sweenenator" Sweeney and Peter-- 0.07885

Notes:

• The effect of temperature on the solubility of solids in liquids is more difficult to predict
• increasing the temperature increases the solubility of solids
• equivalent temperature increase can result in a large increase in solubility for some solvents and only a slight change for others
• in some cases, solubility of a solid decreases with an increase in temperature
• the formation of a solution is accompanied by an energy change.
• if you dissolve some KI in water you will find that the outside of the container feels cold to the touch
• if you dissolve some NaOH in water, the outside of the container feels hot
• the formation of a solid-liquid solution can apparently either absorb or release energy as heat
• before dissolving begins, solvent molecules are held together by intermolecular forces.
• in the solute, molecules are held together by intermolecular forces
• energy is required to separate solute molecules and solvent molecules from their neighbors
• a solute particle that is surrounded by solvent molecules is said to solvated
• the net amount of energy absorbed as eat by the solution when a specific amount of solute dissolves in a solvent is the enthalpy of solution
• the enthalpy of solution is negative (energy released) when the sum of attractions from Steps 1 and 2 is less than Step 3
• the enthalpy of solution is positive (energy absorbed) when the sum of attractions from steps 1 and 2 is less than Step 3
• the concentration of a solution is a measure of the amount of solute in a given amount of solvent or solution
• "dilute" just means that there is a relatively small amount of solute in a solvent
• note that these terms are unrelated to the degree to which a solution is saturated. a saturated solution of a substance that is not very soluble might be very dilute
• Molarity is the number of moles per solute in one liter of a solution
• to relate the molarity of a solution to the mass of solute present, you must know the molar mass of the solute. for example, a "one molar" solution of NaOH contains one mole of NaOH in every liter of solution
• the symbol for molarity is M, and the concentration of one molar solution of sodium hydroxide is written as 1 M NaOH
• one mole of NaOH has a mass of 40.0 g. If this quantity of NaOH is dissolved in enough water to make exactly 1.00 L of solution, the solution is a 1 M solution

molarity (M) = amount of solute (mol)/volume of solution (L)

• note that a 1 M solution is not made by adding 1 mol of solute to 1 L of solvent. in such a case, the final total volume of the solution might not be 1 L.
• the resulting solution is carefully diluted with more solvent to bring the total volume to 1 L
• see pages 420 and 421 for the answers and explanations of Sample Problems A, B, and C
• the lab is due tomorrow. dont forget to find the class avg and % error of the class average, as well as writing your conclusion

Notes from Wednesday, March 24, 2010

So, we started the day off with some demonstrations that taught us a few things. For instance, the volume of a mixture of two liquids is not necessarily the sum of the volume of its components, supersaturated solutions form crystals when disturbed by the addition of more solute, and water and methanol can be made immiscible by adding a salt (in our case, KCO3). Why? Comment with your theories.

Here's the other things from today.

• Pressure increases the solubility of gas in liquid. Increased pressure causes more gas particles to dissolve in the liquid, and decreased pressure allows more dissolved gas to escape from the liquid.
• Henry's law: The solubility of a gas in a liquid is directly proportional to the partial pressure of that gas on the surface of the liquid.
• The rapid escape of gas from a liquid in which it is dissolved is known as effervesence.
• Unlike a solid, increasing the temperature usually decreases gas solubility.

Since we have a short blog today, I leave you with another video, about the awesomeness of effervesence. Have a good night!