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!

Solubility

Solubility
-every combination of solute and solvent has a limit to the amount of solute that can be dissolved
-depends on nature of solute, solvent, and temperature
-solute molecules leave the solid surface and move around randomly
-when max solubility is reached, the amount of solid dissoluting is the same as the amount crystallizing
-solubility equilibrium- dissolution and crystallization of a solute occur at the same rate
Saturated vs. Unsaturated
-saturated-contains the maximum amount of dissolved solute
-unsaturated-contains any amount less than the maximum amount of dissolved solute
-supersaturated-upon cooling, the solute does not settle out of the solution, creating a solution with more than the maximum amount of solute dissolved at certain conditions
-"Like Dissolves Like"
-dissolution happens between two like substances
-type of bondin
-polarity of molecules
-intermolecular forces
-solutions with water involved as the solvent are hydrated
-liquids that do not dissolve in each other are immiscible
-liquids that dissolve freely in each other are miscible

Chapter 12 Section 2

Section 2 The Solution Process

Factors Affecting the Rate of Dissolution

• Because the dissolution process occurs at the surface of the solute, it can be sped up if the surface area of the solute is increased


• Stirring or shaking helps to disperse solute particles and increase contact between the solute surface. This speeds up the dissolving process


• At higher temperatures, collisions between solvent molecules and solvent are more frequent and are of higher energy than at lower temperature. This helps to disperse solvent molecules among the solvent molecules, and speeds up the dissolving process

Solubility

• If you add spoonful after spoonful of sugar to tea, eventually no more sugar will dissolve
• This illustrates the fact that for every combination of solvent with a solid solute at a given temperature there is a limit to the amount of solid that can be dissolved
• The point at which this limit is reached for any solvent-solute combination is difficult to predict precisely and depends on the nature of the solute, the nature of the solvent and the temperature.
• When a solute is first added to a solvent-solute molecules leave the solid surface and more about at random in the solvent
• As more solute is added, more collisions occur between dissolved solute particles. Some of the solute molecules return to the crystal
• When maximum solubility is reached molecules are returning to the solid form at the same rate at which they are going into the solution
• Solution equilibrium is the physical state in which the opposing processes of dissolution and crystallization of a solute occur at which the same rates

Saturated vs. Unsaturated Solutions

• A solution that contains the maximum amount of dissolved solute is described as a saturated solution
• If more solute is added to a saturated solution it falls to the bottom of that container and doesn't dissolve
• A solution that contains less solute than a saturated solution under the existing conditions is called unsaturated solution
• When a saturated solution is cooled the excess solute usually comes out of solution, leaving the solution at the lower temperature
• But sometimes the excess solute doesn't separate a supersaturated solution is produced which is a solution that contains more dissolved solution that contains a more dissolved solute than a saturated solution under the same conditions
• The solubility of a sub solution is the amount of that sub solution required to form a saturated solution with a specific amount of solvent at a specific temperature
• Solubility's vary widely and must be determined experimentally
• They can be found in chemical hand/books and are usually given as gimmes of solute per 100g of solvent at a given temperature

Solute-Solvent Interactions

• Solubility varies greatly with the type of compound involved
• "Like" dissolves like it is a rough but useful rule for predicting whether one substance will dissolve in another
• What makes substances similar depends on type of bonding, polarity and non polarity of molecules, and intermolecular forces between solute and solvent

Dissolving Ionic Compounds in Aqueous Solutions

• The polarity of water molecules plays an important role in the formation of solutions of ionic compounds in water
• The slightly charged parts of water molecules attract ions in the ionic compounds and surround them to keep them separated from other ions in the solution
• This solution process with water as the solvent is referred to as hydration

Non polar Solvents

• Ionic compounds are generally not soluble in non polar solvents such as carbon tetrachloride and toluene
• The non polar solvent molecules do not attract the ions of the crystal strongly enough to overcome the forces holding the crystal together
• Ionic and non polar substances differ widely in bonding, polarity, and intermolecular forces

Liquid Solutes and Solvents

• Liquids that are not soluble in each other are immiscible
• Liquids that dissolve freely in one another in any proportion are said to be miscible

Test Study Material

Guys, these videos are awesome. I couldn't help but to share them:

http://khanacademy.org/

for these chapter, click on the ones about ideal gases and states of matter. I'm sure the next chapters will have videos, too.

KEEP BLOGGIN'!

acid

today in chemistry, we did the lab where we found the partial pressure of the gas created by the magnesium and and acid. Don't forget to finish your labs over the next couple of days and STUDY FOR THE TEST ON THURSDAY.

Chapter 12 Solutions

Section 1 Types of Mixtures

Solutions

• You know from experience that sugar dissolves in water. Sugar is described as "soluble in water". By soluble we mean capable of being dissolved.
• When sugar dissolves, all its molecules become uniformly disturbed among the water molecules. The solid sugar is no longer visible
• Such a mixture is called a solution. A solution is a homogeneous mixture of two or more substances in a single phase.
• The dissolving medium in a solution is called the solvent and the substances dissolved in a solution is called the solute
• Solutions may exist as gases, liquids, or solids. Therefore many possible solute-solvent combinations between gases, liquids, or solids.
• example: Alloys are solid solutions in which the atoms of two or more metals are uniformly mixed
• Solution = Solvent + Solute

Suspensions

• If the particles in a solvent are so large that they settle out unless the mixture is constantly stirred or agitated, the mixture is called a suspension.
• example: A jar of muddy water consists of soil particles suspended in water. The soil particles will eventually all collect or the bottom of he jar because the soil particles are denser than the solvent
• Particles over 1000mm in diameter are 1000 times as large as atoms molecules, or ions suspensions

Colloids

• Particles that are intermediate in sizes between those in solutions and suspensions from mixtures known are as colloidal dispersions or simply colloids
• The particles in a colloid are small enough to be suspended throughout the solvent by the constant movement of the surrounding molecules
• Colloidal particles make up the dispersed phase, and water is the dispersing medium

Tyndall Effect

• Many colloids look similar to solutions because their particles can not be seen
• The Tyndall Effect is a property that can be used to distinguish between a solution and a colloid

Solutes: Electrolytes Versus Nonelectrolytes

• A substance that dissolves in water to give a solution that conducts electric currents is called an electrolyte
• Any soluble ionic compound such as sodium chloride, is an electrolyte
• The positive and negative ions separate from each other in solution and are free to move, making it possible for an electric current to pass through the solution
• A substance that dissolves in water to give a solution that doesn't conduct electric current is called a nonelectrolyte
• Sugar is an example of a nonelectrolyte
• Neutral solute molecules do not contain mobile charged particles, so a solution of a nonelectrolyte cannot conduct electric currents

Movie Day, No Test

Today, our class was scheduled to take the ch. 10&11 test. Instead Dr. Bautista put in a movie , which i am getting ready to summarize, because we were very good for her. The test was rescheduled for after spring break, though, along with the gas lab. Here are some of the key points stated in the movie:

- In the beginning of the film, a group of scientists discussed some of the volcano eruptions and history of the eruptions at Montserrat, an island in the Lesser Antilles.

- The dangerous part of this volcano is its deadly flow of pyroclast. Pyroclast will burn, crush, and suffocate anything in its way.

- The ash from this volcano prevents any outdoor activity for civilians

- 18000 meteorites hit the earth every year

- Most of this is space junk made from molten rock of planet earth.

- Many pacific islands, like Hawaii, are made from these earth shaping meteorites and volcano lava.

- Studies show that under the plates we live on, there are remains of ancient volcanic rock.

- In this volcanic area, there lives more types of bacteria then people living on earth

- Sedimentary Rock is made from rock being in water, and age of earth.

- Stromatolides are rocks found especially in regions of Australia, that are around 3,000 million years old.

- Volcanic lava will destroy all vegetation in its way

- Africa, Asia, and South America once were bonded togethor as one big supercontinent. Similar rock structures from each of these continents proves this theory.

- At the very bottom of the volcano type ocean floor there are some of the most unique life forms in the entire earth.

- Iceland is the only place where the midatlantic ridge is evident above water.

If I missed anything then comment it

3/1/10

TEST TOMORROW!!

The Chapter 10 and 11 test is tomorrow! Be sure to study, especially calculations! Also tomorrow, an outline of chapter 11 is due. Today we worked on our outlines during class, so here's all the blog notes from this chapter compiled into one to help with your outline:

Please comment with study tips or online quizzes etc.

ch 11

the pressure formula is p=f/a such that p-pressure, f=force, and a is area

always remember that area is squared

the SI unit for area is N which means newton. it will increase the speed of one kilogram mass by one meter per second that that force is applied.

pressure is a force per unit area, therefore pressure of a 500 N on a floor with an Area of 325 cm^2 is:

500 n / 325 cm^2 = 1.5 N/Cm^2

*the greater the force -> greater pressure

*smaller the area-> greater pressure KNOW THOSE TWO THINGS

introduced by Evangelista Toricelli who was constantly picked on by his parents, the ultimate teaser being his girlish name....

water pumps can raise about 34 feet

thought that it must be dependent on weight and weight of air

reasoned that since mercury was 14 times less dense than water, it would be 1/14 of 34 feet

tested it and it in rose 30 in.

pressures can be also measured in units of atmospheres. Because the average pressure is 760 mm of Hg or one torr named after evangelista.

In pascals pressure is exerted by one N on one square meter

Daltons law

the measure of full pressure in a gas is the sum of the measure of partial pressures

- To determine the pressure of a gas inside a collection bottle, you would use this equation, which is an instance of Dalton's Law of Partial Pressure:

- P(atmosphere) = P(gas) + P(water)

- If you raise the bottle until the water levels inside and outside the bottle are the same, the total pressure outside and inside will be the same.

- Reading the atmospheric pressure on a barometer and looking up the value of P(water) at the temperature of the experiment in a table (p. 859 in our book), you can calculate the P(gas).

Sample Problem B

- Oxygen gas from the decomposition of potassium chlorate, KClO3, was collected by water displacement. The barometric pressure and the temperature during the experiment were 731.0 torr and 20.0 degrees C respectively. What was the partial pressure of the oxygen collected?

G: Total Pressure = P(atmosphere) = 731.0 torr

P(water) = 17.5 torr (vapor pressure of water at 20.0 C from table A)

P(atmosphere) = P(oxygen) + P(water) ; solve for P(oxygen)

P(oxygen) = P(atm) - P(water)

substitute: P(oxygen) = 731.0 torr - 17.5 torr = 713.5 torr

- Boyle's Law

- Robert Boyle discovered that doubling the pressure on a sample of gas at constant temperature reduced its volume by 1/2

- explained by the Kinetic-Molecular Theory (Dr. B said to make sure and know this!)

- the pressure of a gas is caused by moving molecules hitting the container walls

- if the volume of the container is decreased, more collisions will occur and the pressure will increase

- if the volume of the container is increased, less collisions will occur and the pressure will decrease

- Boyle's Law states that the volume of a fixed mass of gas varies inversely with the pressure at constant temperature.

- Formula: PV=K (P=pressure, V=volume, K= constant)

-the inverse would be a straight line (V=K/P)

- Because of the transitive property of equality, since two different quantities are equal to the same thing (volume x pressure = K), it can be concluded that two separate sets of conditions are equal to each other (P1V1 = P2V2)

Charles Law (cont)

Charles Law: Volume-Temperature between volume and temperature was discovered by the French scientist Jacques Charles in 1787.

Charles found that the volume changes by 1/273 of the original volume for each Celsius degree, at a constant pressure and at an initial temperature of 0 degrees C.

The temperature 273 is absolute zero and is given a value of zero in the Kelvin temperature scale. The relationship between the two temperature scales is K=273.15 +degrees C.

Charles Law states that the volume of a fixed mass of gas at a constant pressure varies directly with the Kelvin temperature.

Gas volume and Kelvin temperature are directly proportional to each other at constant pressure.

Mathematically, Charles Law can be expressed as: V=KT or V/T=K where V is the volume, T is the Kelvin temperature, and K is a constant. the ratio V/T for any set of volume temperature values always equals the same K.

The equation reflects the fact that volume and temperature are directly proportional to each other at constant pressure.

The form of Charles Law that can be applied directly to most volume- temperature gas problems is: V1/T1 = V2/T2.

V1 and T1 represent initial conditions, and V2 and T2 represent another set of conditions.

Given three of the four values, V1, T1, V2, and T2, you can use this equation to calculate the 4th value for a system at constant pressure.

Gay-Lussacs Law: Pressure Temperature Relationship

At a constant volume, the pressure of a gas increases with increasing temperature.

Gas pressure is the result of collisions of molecules with container walls.

The energyu and frequency of collisions depend on the average kinetic energy of the molecues.

Pressure is directly proportional to Kelvin temperature.

Gay Lussacs Law: The pressure of a fixed mass of gas at constant volume varies directly with the Kelvin temperature.

This law is named after Joseph Gay-Lussac, who discovered it in 1802.

Mathematically, Gay Lussacs Law can be expressed as P=KT or P/T=K where P is pressure, T is the Kelvin temperaure, and K is a constant. The ratio P/T for any set of volume-temperature values always equals the same K.

• Boyle's Law, Charles' Law, and Gay-Lussac's Law can be combined into a single equation that can be used for situations in which temperature, pressure, and volume all vary at the same time.
• This is the combined gas law, PV/T=k, or P1V1/T1=P2V2/T2.
• Each gas law can be derived from the combined gas law when the proper variable is kept constant.
• Sample Problem F can be found in your book.
• In the early 1800s, French chemist Joseph Gay-Lussac observed that 2L hydrogen can react with 1 L oxygen to form 2L water vapor.
• This reaction shows a simple 2:1:2 ratio in the volumes of reactants and products. This same ratio applies to any volume proportions.
• Gay-Lussas's law of combining volumes of gases (that's a mouthful) states that at constant temperature and pressure, the volumes of gaseous reactants and products can be expressed as ratios of small whole numbers.
• 1811: Avogadro explained Gay-Lussac's law of combining volumes of gases without violating Dalton's idea of indivisible atoms.
• Avogadro reasoned that, instead of always being in monoatomic form, when they combine to form products, gas molecules can contain more than one atom.
• Avogadro's law: equal volumes of different gases contain the same number of molecules, at given pressure and temperature. Also, gas volume is directly proportional to the amount of gas at a given temperature or pressure. V=kn.
• Dalton had guessed that the formula for water was HO, but Avogadro's reasoning established that water must contain twice as many hydrogen atoms as oxygen atoms because of the volume ratios in which the gases combine.
• Ergo, Avogadro's idea of diatomic gases was consistent with all other knowledge and laws.

• You can use the volume ratios as conversion factors in gas stoichiometry problems as you would mole ratios.
• Ideal Gas Law
• You have learned about equations describing the relationships between 2 or 3 of the 4 variables - Pressure, Volume, Temperature and number of moles - needed to describe a sample at a time.
• All of the laws you have learned thus far can be combined into a single equation, the IDEAL GAS LAW: the mathematical relationship among pressure, volume, temperature, and number of moles of a gas.
• R is a constant
• PV=nRT
• In the equation representing the Ideal gas law, R = idea gas constant
• Its value depends on the units chosen for pressure, volume, and temperature in the rest of the equation.
• Measured values of P, V, Temp., and n for a gas at near-ideal conditions can be used to calculate R
• R = 0.082058

At the begining of the lab Dr. B will give us the barometric pressure, but not the units we need, we will have to convert it as part of the lab.
During the lab there will be no chewing on any substances. HCl will be used during the lab and it will burn your skin.
......................................................Missed some info...................................................
Add HCl the the tube then hold the tube with HCl at an angle when squeezing the water slowly into the tube, try not to let the water and HCl mix because it will cause the reaction to go slower. When putting the capper and magnesium in the tube put it in close to the top and not far in the tube. Then you put your finger over the top of the tube and flip it over and into the beaker with water. It should start to bubble and gas will start to form at the what used to be the bottom of the tube, now the top.
NOTES - CH11 sec 3 cont.
The Ideal Gas Law cont.
The Ideal Gas Constant cont.

• The calculated value of R is usually rounded to 0.0821(L x atm)(md x k)
• Dr. B wants Rto equal 0.08206
• use this value in ideal gas law calculations when the volume is in liters, the preasure is in atmospheres, and the temp is in kelvins
• The ideal gas law canbe applied to determine the existing conditions of a gas sample when three of the four values; P,T,V, and n; are known
• be sure to match the units of the known quantities and the units of R
• Sample problem 1: what is the pressure in atmospheres exerted by a 0.500mol smple of nitrogen gas in a 10.0 L container at 298K?........P=nRT/V..........P=(0.500mol)(0.08206L x atm)(298K)/10.0L 122atm

Graham's Law of Efusion

• Rates of effusion and diffusion depend on the relative velocities of gas molecules. the velocity of a gas varies inversely with the square root of its molar mass.
• recall that the average kinetic energy of the molecules in any gas depends on the temperature and equalys(1/2)mv^2
• for 2 different gases, A and B, at the same temperature, the following relationship is true 1/2 MaVa^2= 1/2 MbVb^2
• from the equation relationg the kinetic energy of two different gases at the same conditions, one can derive an equation relating the rates of effusion of two gases with their molecular mass. Rate of effusion of A/rate of effusion of B= square root of Mb/ square root of Ma
• this equation is known as Graham's law of effusion which states that the rates of effusion of gasses at the same temperature and pressure are inversely proportional to the square roots of their molar mass