Major Concepts• Solids, Liquids, and Gases
• Pressure Conversions • Boyle's Law • Charles's Law • Parts of a Solution • Solubility and Polarity • Concentration of a Solution • Concentrated vs. Dilute (dilution formula) • Mass Percent formula |
Example Calculations1. A 2.5L sample of Freon-12 had a pressure of 56 torr. If the pressure is change to 125 torr, what is the new volume (if the temperature is consistent)?
Answer: 1.1L 2. A 3.5L sample of air is collected at 300 K and then is cooled to 258 K. The pressure is held constant. Does the volume increase or decrease? Answer: Decrease 3. Using the information from the problem above, calculate the new volume of the sample. Answer: 3.0L 4. What is the pressure in atm if the pressure was measured at 37 psi? Answer: 2.5 atm 5. You have a tire that has a volume of 29.0L. The pressure of the tire was a 34.4 psi with the temperature being 78.4ºC. What is the new pressure on the tire when the temperature was increased to 101.9ºC? The new volume of the tire was determined to be 29.5L Answer: 36.1 psi 6. A sample of Xe gas with a volume of 420ml at 785mm Hg is compressed at constant temperature until the volume is 123 ml. What will the new pressure be? Answer: 2.7x10^3 mm Hg 7. Identify the solvent and the solute in this substance: saltwater Answer: solvent- water; solute- salt 8. A solution is prepared by dissolving 5.0 grams of sodium chloride into 50. grams of water. What is the mass percent of NaCl? Answer: 9.0% PRESSURE CONVERSIONS1 atm = 760mm Hg
1 atm = 760 torr 1 atm = 14.7 psi 1 atm = 101,325 Pa |
Boyle's Law: P1V1=P2V2
Robert Boyle was one of the first scientists to study gas laws.
He proposed that pressure and volume are inversely proportional.
** assumes that mass and temperature are constant
Charles's Law: V1/T1 = V2/T2
Jaques Charles showed that the volume of a given amount of gas at constant pressure will increase with the temperature of the bass.
In other words, temperature is proportional to volume.
** assumes that mass and pressure are constant
Combined Gas Law: P1V1/T1 = P2V2/T2
This law combines both Boyle's Law and Charles's Law.
**assumes that the number of moles is constant
Avogadro's Law: V1/n1 = V2/n2
This law states that there is a relationship between the volume and the number of molecules present in the gas sample.
**assumes that temperature and pressure are constant
Ideal Gas Law: PV=nRT
The ideal gas law was derived from the observations from Boyle's, Charles's, and Avogadro's Laws.
**assumes that the gas is ideal
What is an ideal gas?
•1) Ideal gases consist of tiny particles
•2) These particles are so small, compared with the distances between them, that the volume of the individual particles can be assumed to be zero
•3) The particles are in constant random motion, colliding with the walls of the container. The collision with the walls cause the pressure exerted by gas
•4) The particles are assumed not to attract or repel each other
•5) The average kinetic energy of the gas particles is directly proportional to the Kelvin temperature of the gas
Here we are introduced to a new letter... R. R= .08206 L*atm/mol*K
Dalton's Law of Partial Pressure: Ptotal=P1 + P2 +....
John Dalton was one of the first scientists to study mixtures of gases.
For a mixture of gases in a container, the total pressure exerted is the sum of the partial pressures of the gases present.
Parts of a SolutionThere are two parts to a solution:
1- Solvent: the substance that is present in the largest amount 2- Solute: the substance that is dissolved into the solvent; the substance that is present in the smallest amount **Note: In an aqueous solution, the solvent is ALWAYS water! Concentration of a SolutionConcentration (Molarity) is denoted by the symbol M.
M=mol/L Molarity is important when doing liquid stoichiometry problems. It will be your conversion factor between liters of a solution and moles. Every soluble substance has a limit on how much solute can be added before it stops dissolving. When a solution reaches its limit of solute, it is called saturated. If the soluble substance has not yet reached its limit of how much solute it can take, it is unsaturated. By heating a solution up (adding energy) we can sometimes supersaturate it. Supersaturation occurs when a solution is forced to dissolve more solute than it can normally handle under regular circumstances such as standard temperature and pressure. |
Solubility and PolarityWhen determining whether or not a certain compound will be able to dissolve into a certain solvent, keep this phrase in mind: "like dissolves like." Therefore, nonpolar solutes can only dissolve in nonpolar solvents and polar solutes can only dissolve in polar solutes.
How can I tell if a certain compound is polar? There are a few ways to tell if the compound you are looking at is polar: 1) The compound has a charge- If you can tell that the compound in question has a charge, positive or negative, then it is polar. 2) The compound contains O or S- If you see that your compound contains either Oxygen or Sulfur, it is polar. 3) The compound contains one or more halogens- If the compound you are looking at contains Fl, Cl, Br, or any other halogens, it's polar. **Note: a compound doesn't have to have ALL of these traits to be polar. It only needs to have one! Concentration vs. DilutionThe more concentration a solution has, the more concentrated it is.
By adding water to a concentrated substance, you can dilute it. Dilution Formula: C1V1=C2V2 Mass PercentTo find out what percent of a solution a certain solute takes up, you can use the mass percent formula.
Mass %= mass of solute/mass of entire solution x 100 |
Online Resources
Charles's Law: http://www.iun.edu/~cpanhd/C101webnotes/gases/charleslaw.html
The Chemistry of Solutions (this page has pretty much all you need to know about solutions): http://water.me.vccs.edu/courses/env211/lesson8_3.htm
The Chemistry of Solutions (this page has pretty much all you need to know about solutions): http://water.me.vccs.edu/courses/env211/lesson8_3.htm
Video Resources
Dalton's Law of Partial Pressure: http://www.youtube.com/watch?v=AnHrWzN6T10
Boyle's Law: http://www.youtube.com/watch?v=_yS8M3gjjV4
Solutions Song: http://www.youtube.com/watch?v=AyCvICluBM0
Saturation of Solutions: http://www.youtube.com/watch?v=_gNpeZXIHRI
Boyle's Law: http://www.youtube.com/watch?v=_yS8M3gjjV4
Solutions Song: http://www.youtube.com/watch?v=AyCvICluBM0
Saturation of Solutions: http://www.youtube.com/watch?v=_gNpeZXIHRI
Activity Resources
Practicing Boyle's Law: http://www.chm.davidson.edu/vce/gaslaws/boyleslawcalc.html
Molarity practice: http://www.chemteam.info/Solutions/Molarity.html
Molarity practice: http://www.chemteam.info/Solutions/Molarity.html